Fluke 5725A Instruction Manual

© 1993, 1996 Fluke Corporation, All rights reserved. Printed in U.S.A. All product names are trademarks of their respective companies.

Chapter Title Page 1 Introduction and Specifications........................................................ 1-1 1-1. Introduction .......................................................................................... 1-3 1-2. Where to Go From Here....................................................................... 1-4 1-3. How to Use the Manuals. ..................................................................... 1-5 1-4. 5725A Instruction Manual ............................................................... 1-5 1-5. 5700A Operator Manual .................................................................. 1-5 1-6. 5700A Operator Reference Guide ................................................... 1-5 1-7. 5700A Remote Programming Reference Guide............................... 1-5 1-8. 5700A Service Manual..................................................................... 1-6 1-9. Specifications ....................................................................................... 1-6 2 Installation.......................................................................................... 2-1 2-1. Introduction .......................................................................................... 2-3 2-2. Unpacking and Inspection.................................................................... 2-3 2-3. Service Information.............................................................................. 2-5 2-4. Placement and Rack Mounting............................................................. 2-5 2-5. Cooling Considerations........................................................................ 2-5 2-6. Connecting to the 5700A Calibrator .................................................... 2-6 2-7. Selecting Line Voltage......................................................................... 2-7 2-8. Accessing the Fuse............................................................................... 2-8 2-9. Connecting to Line Power.................................................................... 2-9 3 Operating Notes................................................................................. 3-1 3-1. Introduction .......................................................................................... 3-3 3-2. Front Panel Features............................................................................. 3-4 3-3. Rear Panel Features.............................................................................. 3-6 3-4. Turning on the 5725A Amplifier.......................................................... 3-8 3-5. Warm Up .............................................................................................. 3-8 3-6. 5725A Operating Functions and Modes............................................... 3-9 3-7. Standby............................................................................................. 3-9 3-8 Voltage Standby............................................................................... 3-10 3-9. Current Standby ............................................................................... 3-11 3-10. Voltage Operate ............................................................................... 3-12 3-11. Current Operate................................................................................ 3-13 3-12. Conditions That Activate the 5725A.................................................... 3-14

4-1. Introduction .......................................................................................... 4-3 4-2. Overall Functional Description............................................................ 4-3 4-3. 1100V AC Range Functional Description ....................................... 4-5 4-4. 11A Range Functional Description.................................................. 4-6 4-5. Operation in the 11A DC Range.................................................. 4-7 4-6. Operation in the 11A AC Range.................................................. 4-7 4-7. Voltage and Current Standby Modes............................................... 4-7 4-8. Voltage Standby........................................................................... 4-7 4-9. Current Standby........................................................................... 4-7 4-10. How the 5700A and 5725A Communicate ...................................... 4-8 4-11. Description of the Out-Guard Lines (5725A Side) ..................... 4-8 4-12. Description of the In-Guard Lines............................................... 4-9 4-13. Functional Summaries by Assembly................................................ 4-10 4-14. Detailed Circuit Description ................................................................ 4-11 4-15. Interconnect Assembly (A1) ............................................................ 4-11 4-16. Power Supply Assembly (A4).......................................................... 4-12 4-17. High Voltage Supply Section ...................................................... 4-13 4-18. Switching Section........................................................................ 4-14 4-19. Current-Limit Section.................................................................. 4-15 4-20. System Supply Section ................................................................ 4-15 4-21. Fan Supply Section...................................................................... 4-16 4-22. Digital Assembly (A5)..................................................................... 4-16 4-23. Microcomputer ............................................................................ 4-16 4-24. External RAM.............................................................................. 4-16 4-25. External ROM.............................................................................. 4-16 4-26. EEROM ....................................................................................... 4-18 4-27. Data Latch.................................................................................... 4-18 4-28. Strobe Lines................................................................................. 4-18 4-29. Led Driver.................................................................................... 4-18 4-30. Optoisolator Link......................................................................... 4-18 4-31. Break-Detect Circuitry................................................................. 4-19 4-32. Power Up and Reset Circuitry..................................................... 4-19 4-33. Watchdog Timer.......................................................................... 4-19 4-34. Current Amplifier Assembly (A2) ................................................... 4-19 4-35. Error Amplifier Section............................................................... 4-21 4-36. Output Stage Section ................................................................... 4-22 4-37. Monitor Section........................................................................... 4-22 4-38. Control and Switching Section.................................................... 4-23 4-39. Power Supply Section.................................................................. 4-23 4-40. High Voltage Amplifier (A3)........................................................... 4-24 4-41. Input Amplifier ............................................................................ 4-24 4-42. Integrator...................................................................................... 4-26 4-43. Window Comparator ................................................................... 4-26 4-44. Input Clamp ................................................................................. 4-26 4-45. Transconductance and Cascode Stage......................................... 4-27 4-46. Midstage ...................................................................................... 4-27 4-47. Midstage -400V Filter ................................................................. 4-27 4-48. High Voltage Heat Sink Assemblies ........................................... 4-27 4-49. Autobias Current Source ............................................................. 4-28 4-50. Autobias Sense Circuit ................................................................ 4-28 4-51. High Voltage Amplifier Feedback............................................... 4-29 4-52. Signal Transformers .................................................................... 4-29 4-53. Temperature Monitoring.............................................................. 4-29

4-55. Sense Amplifier Section .............................................................. 4-32 4-56. Analog Monitor Section .............................................................. 4-34 4-57. Serial Interface/Guard Crossing Section ..................................... 4-35 4-58. Analog Input Switching Section.................................................. 4-35 4-59. Control Section............................................................................ 4-36 4-60. AC Line Voltage Selection Section............................................. 4-37 5 Calibration and Verification .............................................................. 5-1 5-1. Introduction .......................................................................................... 5-3 5-2. Where to Find Further Information...................................................... 5-3 6 Maintenance ....................................................................................... 6-1 6-1. Introduction .......................................................................................... 6-3 6-2. Replacing the Fuse ............................................................................... 6-3 6-3. Cleaning the Air Filter.......................................................................... 6-4 6-4. General Cleaning.................................................................................. 6-5 6-5. Cleaning PCA’s..................................................................................... 6-5 6-6. Access Procedures................................................................................ 6-6 6-7. Initial Access Procedure .................................................................. 6-7 6-8. Accessing the Power Supply Assembly (A4) .................................. 6-9 6-9. Accessing the Digital Assembly (A5).............................................. 6-9 6-10. Accessing the Current Amplifier Assembly (A2)............................ 6-11 6-11. Accessing the High Voltage Amplifier (A3) ................................... 6-12 6-12. Accessing the High Voltage Sense Assembly (A6)......................... 6-13 6-13. Accessing the High Voltage Output Transistors.............................. 6-14 6-14. Accessing the Interconnect Assembly (A1)..................................... 6-14 6-15. Enabling Front or Rear Binding Posts.................................................. 6-15 7 Troubleshooting................................................................................. 7-1 7-1. Introduction .......................................................................................... 7-3 7-2. 5725A Fault Codes............................................................................... 7-3 7-3. Self Diagnostics.................................................................................... 7-3 7-4. Manual Tests for Fault Isolation .......................................................... 7-6 7-5. Problems 1 or 2: Fault at Power-Up or When Entering Voltage Standby............................................................................... 7-7 7-6. Problem 3: Fault When Entering Voltage Operate.......................... 7-8 7-7. Problem 4: Fault When Entering Current Standby.......................... 7-8 7-8. Problem 5: Fault When Entering Current Operate .......................... 7-8 7-9. Reduced-Voltage Troubleshooting Mode ............................................ 7-8 7-10. Testing the Power Supply By Itself...................................................... 7-9 8 List of Replaceable Parts .................................................................. 8-1 8-1. Introduction .......................................................................................... 8-3 8-2. How to Obtain Parts ............................................................................. 8-3 8-3 Manual Status Information................................................................... 8-3 8-4. Newer Instruments................................................................................ 8-3 8-5. Service Centers..................................................................................... 8-4 9 Schematic Diagrams.......................................................................... 9-1 Index

Table Title Page 2-1. Standard Equipment............................................................................................... 2-3 2-2. Line Power Cord Types Available from Fluke...................................................... 2-4 3-1. Front Panel Features .............................................................................................. 3-5 3-2. Rear Panel Features ............................................................................................... 3-7 4-1. Internal Fuse Data.................................................................................................. 4-13 4-2. Signal Transformer Usage ..................................................................................... 4-29 4-3. High-Quality Reference Name Destination........................................................... 4-33 4-4. Signals Monitored by the Analog Monitor Section............................................... 4-34 7-1. 5725A Fault Codes ................................................................................................ 7-4 7-2. Analog Monitor Faults........................................................................................... 7-7 8-1. Final Assembly ...................................................................................................... 8-4 8-2. A1 Interconnect PCA............................................................................................. 8-14 8-3. A2 Current Amplifier PCA.................................................................................... 8-16 8-4. A3 High Voltage Amplifier PCA .......................................................................... 8-20 8-5. A4 Power Supply PCA .......................................................................................... 8-24 8-6. A5 Digital PCA...................................................................................................... 8-28 8-7. A6 High Voltage Sense PCA................................................................................. 8-30 8-8. A12 Transformer Enclosure Assembly.................................................................. 8-34 8-9. A30 Inductor PCA ................................................................................................. 8-39

Figure Title Page 2-1. Line Power Cords Available for Fluke Instruments.............................................. 2-4 2-2. Correct Way to Dress Interface Cable................................................................... 2-6 2-3. Line Power Label and Switch Location................................................................. 2-7 2-4. Accessing the Fuse ................................................................................................ 2-8 3-1. Front Panel Features .............................................................................................. 3-4 3-2. Rear Panel Features ............................................................................................... 3-6 4-1. 5725A Overall Block Diagram.............................................................................. 4-4 4-2. Digital Assembly Block Diagram.......................................................................... 4-17 4-3. Current Amplifier Assembly Block Diagram........................................................ 4-20 4-4. High Voltage Amplifier Assembly Block Diagram............................................... 4-25 4-5. High Voltage Sense Assembly Block Diagram..................................................... 4-31 6-1. Accessing the Fuse ................................................................................................ 6-4 6-2. Accessing the Air Filter......................................................................................... 6-5 6-3. Assembly Location Diagram ................................................................................. 6-6 6-4. Initial Access Procedure ........................................................................................ 6-8 6-5. Accessing the Digital Assembly............................................................................ 6-10 6-6. Correct Way to Dress Cables................................................................................. 6-12 6-7. Enabling Front or Rear Binding Posts................................................................... 6-16 8-1. Final Assembly ...................................................................................................... 8-6 8-2. A1 Interconnect PCA............................................................................................. 8-15 8-3. A2 Current Amplifier PCA.................................................................................... 8-19 8-4. A3 High Voltage Amplifier PCA .......................................................................... 8-23 8-5. A4 Power Supply PCA .......................................................................................... 8-27 8-6. A5 Digital PCA...................................................................................................... 8-29 8-7. A6 High Voltage Sense PCA................................................................................. 8-33 8-8. A12 Transformer Enclosure Assembly.................................................................. 8-35 8-9. A30 Inductor PCA ................................................................................................. 8-40 9-7. A12 Transformer Enclosure Assembly.................................................................. 9-3

accordance with the manufacturer’s instructions, may cause interference to radio and television reception. It has been type tested and found to comply with the limits for a Class B computing device in accordance with the specifications of Part 15 of FCC Rules, which are designed to provide reasonable protection against such interference in a residential installation. Operation is subject to the following two conditions: • This device may not cause harmful interference. • This device must accept any interference received, including interference that may cause undesired operation. There is no guarantee that interference will not occur in a particular installation. If this equipment does cause interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one of more of the following measures: • Reorient the receiving antenna • Relocate the equipment with respect to the receiver • Move the equipment away from the receiver • Plug the equipment into a different outlet so that the computer and receiver are on different branch circuits If necessary, the user should consult the dealer or an experienced radio/television technician for additional suggestions. The user may find the following booklet prepared by the Federal Communications Commission helpful: How to Identify and Resolve Radio-TV Interference Problems. This booklet is available from the U.S. Government Printing Office, Washington, D.C. 20402. Stock No. 004-000-00345-4. Declaration of the Manufacturer or Importer We hereby certify that the Fluke Model 5725A Amplifier is in compliance with BMPT Vfg 243/1991 and is RFI suppressed. The normal operation of some equipment (e.g. signal generators) may be subject to specific restrictions. Please observe the notices in the users manual. The marketing and sales of the equipment was reported to the Central Office for Telecommunication Permits (BZT). The right to retest this equipment to verify compliance with the regulation was given to the BZT. Bescheinigung des Herstellers/Importeurs Hiermit wird bescheinigt, daβ Fluke Models 5725A Amplifier in Übereinstimung mit den Bestimmungen der BMPT-AmtsblVfg 243/1991 funk-entstört ist. Der vorschriftsmäßige Betrieb mancher Geräte (z.B. Meßsender) kann allerdings gewissen Einschränkungen unterliegen. Beachten Sie deshalb die Hinweise in der Bedienungsanleitung. Dem Bundesamt für Zulassungen in der Telekcommunikation wurde das Inverkehrbringen dieses Gerätes angezeigt und die Berechtigung zur Überprüfung der Seire auf Einhaltung der Bestimmungen eingeräumt. Fluke Corporation

LETHAL VOLTAGE may be present on the terminals, observe all safety precautions! To avoid electrical shock hazard, the operator should not electrically contact the output hi or sense hi binding posts. During operation, lethal voltages of up to 1100V ac or dc may be present on these terminals. Whenever the nature of the operation permits, keep one hand away from equipment to reduce the hazard of current flowing thought vital organs of the body. Terms in this Manual This instrument has been designed and tested in accordance with IEC Publication 348, Safety Requirements for Electronic Measuring Apparatus. This manual contains information and warnings which have to be followed by the user to ensure safe operation and to retain the instrument in safe condition. Warning statements identify conditions or practices that could result in personal injury or loss of life. Caution statements identify conditions or practices that could result in damage to the equipment or other property.

DANGER — High Voltage Protective ground (earth) terminal Attention — refer to the manual. This symbol indicates that information about the usage of a feature is contained in the manual. Power Source The 5725A is intended to operate from a power source that will not apply more than 264V ac rms between the supply conductors or between either supply conductor and ground. A protective ground connection by way of the grounding conductor in the power cord is essential for safe operation. Use the Proper Fuse To avoid fire hazard, use only the fuse specified on the line voltage selection switch label, and which is identical in type voltage rating, and current rating. Grounding the 5725A The 5725A is Safety Class I (grounded enclosure) instruments as defined in IEC 348. The enclosure is grounded through the grounding conductor of the power cord. To avoid electrical shock, plug the power cord into a properly wired earth grounded receptacle before connecting anything to any of the 5725A or 5700A terminals. A protective ground connection by way of the grounding conductor in the power cord is essential for safe operation. Use the Proper Power Cord Use only the power cord and connector appropriate for proper operation of a 5725A in your country. Use only a power cord that is in good condition. Refer cord and connector changes to qualified service personnel. Do Not Operate in Explosive Atmospheres To avoid explosion, do not operate the 5725A in an atmosphere of explosive gas. Do Not Remove Cover To avoid personal injury or death, do not remove the 5725A cover. Do not operate the 5725A without the cover properly installed. There are no user-serviceable parts inside the 5725A, so there is no need for the operator to ever remove the cover. Do Not Attempt to Operate if Protection May be Impaired If the 5725A appears damaged or operates abnormally, protection may be impaired. Do not attempt to operate it. When is doubt, have the instrument serviced.

PERSONNEL ONLY Also refer to the preceding Operator Safety Summary Do Not Service Alone Do not perform internal service or adjustment of this product unless another person capable of rendering first aid and resuscitation is present. Use Care When Servicing With Power On Dangerous voltage exist at many points inside this product. To avoid personal injury, do not touch exposed connections and components while power is on. Whenever the nature of the operation permits, keep one hand away from equipment to reduce the hazard of current flowing through vital organs of the body. Do not wear a grounded wrist strap while working on this product. A grounded wrist strap increase the risk of current flowing through the body. Disconnect power before removing protective panels, soldering, or replacing components. High voltage may still be present even after disconnecting power.

ELECTRIC SHOCK Free the Victim From the Live Conductor Shut off high voltage at once and ground the circuit. If high voltage cannot be turned off quickly, ground the circuit. If the circuit cannot be broken or grounded, use a board, dry clothing, or other nonconductor to free the victim. Get Help! Yell for help. Call an emergency number. Request medical assistance. Never Accept Ordinary and General Tests for Death Symptoms of electric shock may include unconsciousness, failure to breathe, absence of pulse, pallor, and stiffness, and well as severe burns. Treat the Victim If the victim is not breathing, begin CPR or mouth-to-mouth resuscitation if you are certified.

Title Page 1-1. Introduction .......................................................................................... 1-3 1-2. Where to Go From Here....................................................................... 1-4 1-3. How to Use the Manuals ...................................................................... 1-5 1-4. 5725A Instruction Manual ............................................................... 1-5 1-5. 5700A Operator Manual .................................................................. 1-5 1-6. 5700A Operator Reference Guide ................................................... 1-5 1-7. 5700A Remote Programming Reference Guide............................... 1-5 1-8. 5700A Service Manual..................................................................... 1-6 1-9. Specifications ....................................................................................... 1-6

Introduction 1 1-3 Introduction 1-1. The Fluke 5725A Amplifier enhances the 5700A Calibrator in the ac voltage, ac current, and dc current functions. The 5725A operates under complete control of the 5700A through an interface cable supplied with the 5725A. A diagram in the specifications tables at the end of this section illustrates the extended ac volt-hertz product achieved by using a 5725A. Increased ac voltage load limits allow using the 5700A Calibrator in systems with long cables. Voltage output from the 5725A is available at the 5700A Calibrator front or rear binding posts. This eliminates the need to move cables during a procedure that requires amplified as well as standard calibrator outputs. The 5725A front or rear panel OUTPUT binding posts are only for current output. Extended-range ac and dc current is supplied through them. Since most meters with a high current range use a separate high current input terminal, this configuration normally eliminates the need to move cables during a procedure. If a single-point current output is needed, the 5700A Calibrator can be configured to source all current outputs through the 5725A binding posts. Enhancements to 5700A ac voltage output capability provided by the 5725A are as follows: • Frequency limits at higher voltage increase to 100 kHz at 750V, 30 kHz at 1100V. • Load limits are to 70 mA for frequencies above 5 kHz, and to 50 mA for frequencies less than 5 kHz. • Capacitive load limits are increased to 1000 pF. Model 5725A operating functions and ranges are as follows: • AC voltage: 220 to 1100V rms up to 70 mA (50 mA < 5 kHz), 40 Hz to 30 kHz; 220 to 750V rms up to 70 mA, 30 kHz to 100 kHz • DC current: 0 to ±11A • AC current: 1 to 11A rms, 40 Hz to 10 kHz

1-2. This manual is the operator and service manual for the 5725A. However, because the 5725A operates under the control of the 5700A Calibrator, most operating instructions for the 5725A are in the 5700A manuals. Topics such as selecting output values, connecting to a UUT (Unit Under Test), and self calibration are covered in the 5700A Operator Manual. The list below gives some specific pointers, and the text further on describes how to use all the manuals to find 5725A information. For More Information About: Refer To: • Unpacking and setup Section 2 of this manual • Installation and rack mounting Section 2 of this manual and the Y5735/Y5737 Instruction Sheet • AC line power and interface cabling Section 2 of this manual • Controls, indicators, and binding posts Section 3 of this manual • 5725A service information Sections 4 through 9 of this manual • Operating the amplifier Section 3 of this manual and Section 4 of the 5700A Operator Manual • Cabling to a Unit Under Test Section 4 of the 5700A Operator Manual • Self calibration Section 7 of the 5700A Operator Manual • Full verification Section 3 of the 5700A Service Manual • IEEE-488 or serial remote operation Section 5 of the 5700A Operator Manual • 5700A/5725A specifications Section 1 of this manual • Theory of operation Section 4 and 9 of this manual • Troubleshooting Section 6 of this manual • Ordering a part Section 8 of this manual

How to Use the Manuals 1 1-5 How to Use the Manuals 1-3. The following paragraphs describe how each manual addresses the 5725A. 5725A Instruction Manual 1-4. Use the 5725A Instruction Manual for installing the 5725A, learning about its front and rear panel features, and for all service-related topics such as maintenance, troubleshooting, parts lists, and schematics. (The 5725A Instruction Manual is the service and operator manual for the 5725A.) Although the instruction manual also contains a section devoted to 5725A operating notes, once the 5725A is up and running you will find that the 5700A Operator Manual contains most of the information you need to operate the 5725A. 5700A Operator Manual 1-5. The 5700A Operator Manual contains the following information pertaining to the 5725A: • Specifications for both the 5700A and 5725A (these same specifications are in this Instruction Manual) • Cable connections to a UUT for amplified voltage and current • Front panel (local) operation • Remote control operation, IEEE-488 or RS-232 • Self calibration • Fault codes (these appear on the 5700A Control Display, or are read from the 5700A in remote control operation) • Calibration constant symbolic names • Glossary of calibration-related terms The 5700A Operator Manual comes with two pocket-sized booklets: one for front panel operation and one for remote programming. 5700A Operator Reference Guide 1-6. The 5700A Operator Reference Guide contains a summary of operating instructions from the Operator Manual. This booklet contains information needed to start up and operate the 5700A, but since the 5700A controls the 5725A, much of this information applies to the 5725A. The booklet is included in the binder with the 5700A Operator Manual. 5700A Remote Programming Reference Guide 1-7. The 5700A Remote Programming Reference Guide contains a summary of remote commands for the 5700A. It also contains information needed to determine system status using the status byte and registers. Remote commands and system status apply to a 5725A under control of the 5700A. This booklet is also included in the binder with 5700A Operator Manual.

1-8. The 5700A Service Manual is a maintenance guide for the 5700A. The following 5725A topics are included in the 5700A Service Manual: • Specifications for both the 5700A and 5725A (these same specifications are in this Instruction Manual) • Full verification of the 5700A and 5725A (recommended every two years) • Calibration of the 5700A and 5725A (same procedure as in the 5700A Operator Manual) Specifications 1-9. Specifications are valid after allowing a warm-up period of 30 minutes, or if the 5725A has been recently on, twice the time the 5725A has been turned off. For example, if the 5725A has been turned off for five minutes, the warm-up period is ten minutes. Absolute uncertainty includes stability, temperature coefficient, linearity, line and load regulation, and traceability to external standards. You do not need to add anything to absolute uncertainty to determine the ratios between 5700A/5725A uncertainties and the uncertainties of your calibration workload. Relative uncertainty specifications are provided for enhanced accuracy applications. These specifications apply when range constants are adjusted (see "Range Calibration" in the 5700A Operator Manual). To calculate absolute uncertainty, you must combine the uncertainties of your external standards and techniques with relative uncertainty. Secondary performance specifications and operating characteristics are included in the uncertainty specifications. They are also provided separately for special calibration requirements such as stability or linearity testing.

Specifications 1 1-7 DC Voltage Absolute Uncertainty ± 5°C from calibration temperature Relative Uncertainty ± 1°C Range Resolution 24 Hours 90 Days 180 Days 1 Year 24 Hours 90 Days ± (ppm output + µV) ± (ppm output + µV) 220 mV 10 nV 6.5 + .75 7 + .75 8 + .75 9 + .8 2.5 + .5 4 + .5 2.2V 100 nV 3.5 + 1.2 6 + 1.2 7 + 1.2 8 + 1.2 2.5 + 1.2 4 + 1.2 11V 1 µV 3.5 + 3 5 + 4 7 + 4 8 + 4 1.5 + 3 3.5 + 4 22V 1 µV 3.5 + 6 5 + 8 7 + 8 8 + 8 1.5 + 6 3.5 + 8 220V 10 µV 5 + 100 6 + 100 8 + 100 9 + 100 2.5 + 100 4 + 100 1100V 100 µV 7 + 600 8 + 600 10 + 600 11 + 600 3 + 600 4.5 + 600 Secondary Performance Specifications and Operating Characteristics Included in Uncertainty Specifications Stability Temperature Coefficient [Note] Noise Range ± 1°C 24 Hours 10°-40°C 0°-10°C and Linearity ± 1°C Bandwidth 0.1-10 Hz Bandwidth 10-10 kHz 40°-50°C pk-pk RMS ± (ppm output + µV) ± (ppm output + µV)/°C ± (ppm output + µV) µV 220 mV 2.2V 11V 22V 220V 1100V .3 + .3 .3 + 1 .3 + 2.5 .4 + 5 .5 + 40 .5 + 200 .4 + .1 .3 + .1 .15 + .2 .2 + .4 .3 + 5 .5 + 10 1.5 + .5 1.5 + 2 1 + 1.5 1.5 + 3 1.5 + 40 3 + 200 1 + .2 1 + .6 .3 + 2 .3 + 4 1 + 40 1 + 200 .15 + .1 .15 + .4 .15 + 2 .15 + 4 .15 + 60 .15 + 300 5 15 50 50 150 500 Note: Temperature coefficient is an adder to uncertainty specifications that does not apply unless operating more than ±5°C from calibration temperature. Minimum output: 0V for all ranges, except 100V for 1100V range Maximum load: 50 mA for 2.2V through 220V ranges; 20 mA for 1100V range; 50Ω output impedance on 220 mV range; all ranges <1000 pF,>25Ω Load regulation: <0.2 ppm + 0.2 µV change, full load to no load Line regulation: <0.1 ppm change, ±10% of selected nominal line Settling time: 3 seconds to full accuracy; + 1 second for range or polarity change; + 1 second for 1100V range Overshoot: <5% Common mode rejection: 140 dB, DC to 400 Hz Remote sensing: Available 0V to ±1100V, on 2.2V through 1100V ranges

Relative Uncertainty ± 1°C 24 Hours 90 Days 180 Days 1 Year 24 Hours 90 Days Hz ± (ppm output + µV) ± (ppm output + µV) 2.2 mV 1 nV 10-20 20-40 40-20k 20k-50k 50k-100k 100k-300k 300k-500k 500k-1M 500 + 5 200 + 5 100 + 5 340 + 5 800 + 8 .11% + 15 .15% + 30 .4% + 40 550 + 5 220 + 5 110 + 5 370 + 5 900 + 8 .12% + 15 .17% + 30 .44% + 4 600 + 5 230 + 5 120 + 5 390 + 5 950 + 8 .13% + 15 .17% + 30 .47% + 40 600 + 5 240 + 5 120 + 5 410 + 5 950 + 8 .13% + 15 .18% + 30 .48% + 40 500 + 5 200 + 5 60 + 5 100 + 5 220 + 8 400 + 15 .10% + 30 .3% + 30 550 + 5 220 + 5 65 + 5 110 + 5 240 + 8 440 + 15 .11% + 30 .33% + 30 22 mV 10 nV 10-20 20-40 40-20k 20k-50k 50k-100k 100k-300k 300k-500k 500k-1M 500 + 6 200 + 6 100 + 6 340 + 6 800 + 8 .11% + 15 .15% + 30 .4% + 40 550 + 6 220 + 6 110 + 6 370 + 6 900 + 8 .12% + 15 .17% + 30 .44% + 4 600 + 6 230 + 6 120 + 6 390 + 6 950 + 8 .13% + 15 .17% + 30 .47% + 40 600 + 6 240 + 6 120 + 6 410 + 6 950 + 8 .13% + 15 .18% + 30 .48% + 40 500 + 6 200 + 6 60 + 6 100 + 6 220 + 8 400 + 15 .10% + 30 .3% + 30 550 + 6 220 + 6 65 + 6 110 + 6 240 + 8 440 + 15 .11% + 30 .33% + 30 220 mV 100 nV 10-20 20-40 40-20k 20k-50k 50k-100k 100k-300k 300k-500k 500k-1M 500 + 16 200 + 10 95 + 10 300 + 10 750 + 30 940 + 30 .15% + 40 .30% + 100 550 + 16 220 + 10 100 + 10 330 + 10 800 + 30 .1% + 30 .17% + 40 .33% + 100 600 + 16 230 + 10 110 + 10 350 + 10 850 + 30 .11% + 30 .17% + 40 .35% + 100 600 + 16 240 + 10 110 + 10 360 + 10 900 + 30 .11% + 30 .18% + 40 .36% + 100 500 + 16 200 + 10 60 + 10 100 + 10 220 + 30 400 + 30 .1% + 40 .3% + 100 550 + 16 220 + 10 65 + 10 110 + 10 240 + 30 440 + 30 .11% + 40 .33% + 100 2.2V 1 µV 10-20 20-40 40-20k 20k-50k 50k-100k 100k-300k 300k-500k 500k-1M 500 + 100 150 + 30 70 + 7 120 + 20 230 + 80 400 + 150 .10% + 400 .20% + 1 mV 550 + 100 170 + 30 75 + 7 130 + 20 250 + 80 440 + 150 .11% + 400 .22% + 1 mV 600 + 100 170 + 30 80 + 7 140 + 20 270 + 80 470 + 150 .12% + 400 .23% + 1 mV 600 + 100 180 + 30 85 + 7 140 + 20 280 + 80 480 + 150 .12% + 400 .24% + 1 mV 500 + 100 150 + 30 40 + 7 100 + 20 200 + 80 400 + 150 .1% + 400 .2% + 1 mV 550 + 100 170 + 30 45 + 7 110 + 20 220 + 80 440 + 150 .11% + 400 .22% + 1 mV 22V 10 µV 10-20 20-40 40-20k 20k-50k 50k-100k 100k-300k 300k-500k 500k-1M 500 + 1 mV 150 + 300 70 + 70 120 + 200 230 + 400 500 + 1.7 mV .12% + 5 mV .26% + 9 mV 550 + 1 mV 170 + 300 75 + 70 130 + 200 250 + 400 550 + 1.7 mV .13% + 5 mV .28% + 9 mV 600 + 1 mV 170 + 300 80 + 70 140 + 200 270 + 400 550 + 1.7 mV .13% + 5 mV .29% + 9 mV 600 + 1 mV 180 + 300 85 + 70 140 + 200 280 + 400 600 + 1.7 mV .14% + 5 mV .30% + 9 mV 500 + 1 mV 150 + 300 40 + 70 100 + 200 200 + 400 500 + 1.7 mV .12% + 5 mV .26% + 9 mV 550 + 1 mV 170 + 300 45 + 70 110 + 200 220 + 400 550 + 1.7 mV .13% + 5 mV .28% + 9 mV ± (ppm output + mV) ± (ppm output + mV) 220V 100 µV 10-20 20-40 40-20k 20k-50k 50k-100k 100k-300k 300k-500k 500k-1M 500 + 10 150 + 3 75 + 1 200 + 4 500 + 10 .15% + 110 .50% + 110 1.20% + 220 550 + 10 170 + 3 80 + 1 220 + 4 550 + 10 .15% + 110 .52% + 110 1.25% + 220 600 + 10 170 + 3 85 + 1 240 + 4 600 + 10 .16% + 110 .53% + 110 1.25% + 220 600 + 10 180 + 3 90 + 1 250 + 4 600 + 10 .16% + 110 .54% + 110 1.30% + 220 500 + 10 150 + 3 45 + 1 100 + 1 300 + 10 .15% + 110 .50% + 110 1.20% + 220 550 + 10 170 + 3 50 + 1 110 + 1 330 + 10 .15% + 100 .52% + 110 1.20% + 220 1100V 11 mV 50-1k 75 + 4 80 + 4 85 + 4 90 + 4 50 + 4 55 + 4 5725A Amplifier: 1100V 1 mV 40-1k 1k-20k 20k-30k 75 + 4 105 + 6 230 + 11 80 + 4 125 + 6 360 + 11 85 + 4 135 + 6 440 + 11 90 + 4 165 + 6 600 + 11 50 + 4 85 + 6 160 + 11 55 + 4 105 + 6 320 + 11 750V 30k-50k 50k-100k 230 + 11 600 + 45 360 + 11 .13% + 45 440 + 11 .16% + 45 600 + 11 .23% + 45 160 + 11 380 + 45 320 + 11 .12% + 45

Specifications 1 1-9 AC Voltage (continued) Secondary Performance Specifications and Operating Characteristics Included in Uncertainty Specifications Stability Temperature Coefficient Maximum Distortion Range Frequency ± 1°C 24 Hours 10°-40°C 0°-10°C and 40°-50°C Output Impedance Bandwidth 10 Hz-10 MHz Hz ± µV ±µV/°C Ω ± (% output + µV) 2.2 mV 10-20 20-40 40-20k 20k-50k 50k-100k 100k-300k 300k-500k 500k-1M 5 5 2 2 3 3 5 5 .05 .05 .05 .1 .2 .3 .4 .5 .05 .05 .05 .1 .2 .3 .4 .5 50 .05 + 10 .035 + 10 .035 + 10 .035 + 10 .035 + 10 .3 + 30 .3 + 30 2 + 30 22 mV 10-20 20-40 40-20k 20k-50k 50k-100k 100k-300k 300k-500k 500k-1M 5 5 2 2 3 5 10 15 .2 .2 .2 .4 .5 .6 1 1 .3 .3 .3 .5 .5 .6 1 1 50 .05 + 11 .035 + 11 .035 + 11 .035 + 11 .035 + 11 .3 + 30 .3 + 30 1 + 30 ± (ppm output + µV) ± (ppm output µV)/°C 220 mV 10-20 20-40 40-20k 20k-50k 50k-100k 100k-300k 300k-500k 500k-1M 150 + 20 80 + 15 12 + 2 10 + 2 10 + 2 20 + 4 100 + 10 200 + 20 2 + 1 2 + 1 2 + 1 15 + 2 15 + 4 80 + 5 80 + 5 80 + 5 2 + 1 2 + 1 2 + 1 15 + 2 15 + 4 80 + 5 80 + 5 80 + 5 50 .05 + 16 .035 + 16 .035 + 16 .035 + 16 .035 + 16 .3 + 30 .3 + 30 2 + 30 Load Regulation ± (ppm output + µV) 2.2V 10-20 20-40 40-20k 20k-50k 50k-100k 100k-300k 300k-500k 500k-1M 150 + 20 80 + 15 12 + 4 15 + 5 15 + 5 30 + 10 70 + 20 150 + 50 50 + 10 15 + 5 2 + 1 10 + 2 10 + 4 80 + 15 80 + 40 80 + 100 50 + 10 15 + 5 5 + 2 15 + 4 20 + 4 80 + 15 80 + 40 80 + 100 10 + 2 10 + 2 10 + 4 30 + 10 120 + 16 300 ppm 600 ppm .12% .05 + 80 .035 + 80 .035 + 80 .035 + 80 .035 + 80 .3 + 110 .3 + 110 1 + 110 22V 10-20 20-40 40-20k 20k-50k 50k-100k 100k-300k 300k-500k 500k-1M 150 + 20 80 + 15 12 + 8 15 + 10 15 + 10 30 + 15 70 + 100 150 + 100 50 + 100 15 + 30 2 + 10 10 + 20 10 + 40 80 + 150 80 + 300 80 + 500 50 + 100 15 + 40 4 + 15 20 + 20 20 + 40 80 + 150 80 + 300 80 + 500 10 + 20 10 + 20 10 + 30 30 + 50 80 + 80 100 + 700 200 + 1.1 mV 600 + 3.0 mV .05 + 700 .035 + 700 .035 + 700 .035 + 700 .035 + 700 .3 + 800 .3 + 800 2 + 800 220V 10-20 20-40 40-20k 20k-50k 50k-100k 100k-300k 300k-500k 500k-1M 150 + 200 80 + 150 12 + 80 15 + 100 15 + 100 30 + 400 100 + 10 mV 200 + 20 mV 50 + 1 mV 15 +300 2 + 80 10 + 100 10 + 500 80 + 600 80 + 800 80 + 1 mV 50 + 1 mV 15 + 300 4 + 80 20 + 100 20 + 500 80 + 600 80 + 800 80 + 1 mV 10 + .2 mV 10 + .2 mV 10 + .3 mV 30 + .6 mV 80 + 3 mV 250 + 25 mV 500 + 50 mV 1000 + 110 mV .05 + 10 mV .05 + 10 mV .05 + 10 mV .05 + 10 mV .1 + 13 mV 1.5 + 50 mV 1.5 + 50 mV 3.5 + 100 mV ±(ppm output + mV) ±(ppm output)/°C ±(% output) 1100V 50-1k 20 + .5 2 5 10 + 1 .07

Secondary Performance and Operating Characteristics (continued) Included in Uncertainty Specifications 5725A Amplifier: Stability Temperature Coefficient Load Regulation Distortion Range Frequency ±1°C 24 Hours 10°-40°C 0°-10°C and 40°-50°C [Note 2] Bandwidth 10 Hz-10 MHz Hz ±(ppm output + mV) ±(ppm output)/°C ±(ppm output + mV) ±(% output) 150 pF 1000 pF 1100V 40-1k 1k-20k 20k-50k 50k-100k 10 + .5 15 + 2 40 + 2 130 + 2 5 5 10 30 5 5 10 30 10 + 1 90 + 6 275 + 11 500 + 30 .10 .10 .30 .40 .10 .15 .30 .40 Voltage Range Maximum Current Limits Load Limits Output display formats: Voltage or dBm, dBm reference 600Ω. 2.2V [Note 1] 22V 220V 50 mA, 0°C-40°C 20 mA, 40°C-50°C >50Ω, 1000 pF Minimum output: 10% on each range External sense: Selectable for 2.2v, 22V, 220V, and 1100V ranges; 5700A <100 kHz, 5725A <30 kHz 1100V 6 mA 600 pF Settling time to full accuracy: 5725A Amplifier: 1000 pF [Note 2] Frequency (Hz) Settling time (seconds) 40 Hz-5 kHz 50 mA <20 7 1100V 5 kHz-30 kHz 70 mA 300 pF 120-120k 5 30 kHz-100 kHz 70 mA [Note 3] 150 pF >120k 2 Notes: 1. 2.2V Range, 100 kHz-1.2 MHz only: uncertainty specifications cover loads to 10 mA or 1000 pF. For higher loads, load regulation is added. 2. The 5725A will drive up to 1000 pF of load capacitance. Uncertainty specifications include loads to 300 pF and 150 pF as shown under "Load Limits." For capacitance’s up to the maximum of 1000 pF, add "Load Regulation." 3. Applies from 0°C to 40°C 100V 220V 22V 3.5V 10 Hz 50 Hz 1 kHz 100 kHz 1 MHz 30 MHz FREQUENCY VOLTAGE VOLT-HERTZ CAPABILITY 40 Hz 30 kHz 5700A 5725A 5205A or 5215A 5700A-03 2.2 x 107 V-Hz + 1 second for amplitude or frequency range change; + 2 seconds for 5700A 1100V range; + 4 seconds for 5725A 1100V range Overshoot: <10% Common mode rejection: 140 dB, DC to 400 Hz Frequency: Ranges (Hz): 10.000-11.999, 12.00-119.99 120.0-1199.9, 1.200k-11.999k 12.00k-119.99k, 120.0k-1.1999 Uncertainty: ±0.01% Resolution: 11.999 counts Phase lock: Selectable rear panel BNC input Phase uncertainty (except 1100V range): >30 Hz: ±1° + 0.05°/kHz), <30 Hz: ±3° Input voltage: 1V to 10V rms sine wave (do not exceed 1V for mV ranges) Frequency range: 10 Hz to 1.1999 MHz Lock range: ±2% of frequency Lock-in time: Larger of 10/frequency or 10 msec Phase reference: Selectable, rear panel BNC output Range: ±180° Phase Uncertainty (except 1100V range): ±1° at quadrature points (0°, ±90°, ±180°) elsewhere ±2° Stability: ±0.1° Resolution: 1° Output level: 2.5V rms ±0.2V Frequency range: 50 kHz to 1 kHz, useable 10 Hz to 1.1999 MHz

Specifications 1 1-11 Resistance Nominal Absolute Uncertainty of Characterized Value ±5°C from calibration temperature [Note 1] Relative Uncertainty ±1°C Value 24 Hours 90 Days 180 Days 1 Year 24 Hours 90 Days Ω ±ppm ±ppm 0 1 1.9 10 19 100 190 1k 1.9k 10k 19k 100k 190k 1M 1.9M 10M 19M 100M 50 µΩ 85 85 26 24 15 15 11 11 9 9 11 11 16 17 33 43 110 50 µΩ 95 95 28 26 17 17 12 12 11 11 13 13 18 19 37 47 120 50 µΩ 100 100 30 28 18 18 13 13 12 12 14 14 20 21 40 50 125 50 µΩ 110 110 33 31 20 20 15 15 14 14 16 16 23 24 46 55 130 50 µΩ 32 25 5 4 2 2 2 2 2 2 2 2 2.5 3.5 10 20 50 50 µΩ 40 33 8 7 4 4 3.5 3.5 3.5 3.5 3.5 3.5 5 6 14 24 60 Secondary Performance Specifications and Operating Characteristics Included in Uncertainty Specifications Nominal Stability Temperature Coefficient [Note 2] Full Spec Load Maximum Maximum Difference of Two-Wire Adder active compensation [Note 4] Value ±1°C 24 Hours 10°-40°C 0°-10°C and Range [Note 3] Peak Current Characterized to Nominal Lead Resistance 40°-50°C Value 0.1Ω 1Ω Ω ±ppm ±ppm/°C mA mA ±ppm ±mΩ 0    8-500 500  2 4 1 32 4 5 8-100 700 500 2 4 1.9 25 6 7 8-100 500 500 2 4 10 5 2 3 8-11 220 300 2 4 19 4 2 3 8-11 160 300 2 4 100 2 2 3 8-11 70 150 2 4 190 2 2 3 8-11 50 150 2 4 1k 2 2 3 1-2 22 150 10 15 1.9k 2 2 3 1-1.5 16 150 10 15 10k 2 2 3 100-500 µA 7 150 50 60 19k 2 2 3 50-250 µA 5 150 100 120 100k 2 2 3 10-100 µA 1 150 190k 2 2 3 5-50 µA 500 µA 150 1M 2.5 2.5 6 5-20 µA 100 µA 200 1.9M 3.5 3 10 2.5-10 µA 50 µA 200 10M 10 5 20 .5-2 µA 10 µA 300 19M 20 8 40 .25-1 µA 5 µA 300 100M 50 12 100 50-200 nA 1 µA 500 Notes: 1. Specifications apply to displayed value. 4-wire connections, except 100 mΩ. 2. Temperature coefficient is an adder to uncertainty specifications that does not apply unless operated more than 5°C from calibration temperature, or calibrated outside the range 19°C to 24°C. Two examples: a) Calibrate at 20°C: Temperature coefficient adder is not required unless operated below 15°C or above 25°C. b) Calibrate at 26°C: Add 2°C temperature coefficient adder. Additional temperature coefficient adder is not required unless operated below 21°C or above 31°C. 3. Refer to current derating factors table for loads outside of this range. 4. Active two-wire compensation may be selected for values less than 100 kΩ, with either the front panel or the meter input terminals as reference plane. Active compensation is limited to 11 mA load, and to 2V burden. Two wire compensation can be used only with Ω meters that source continuous (not pulsed) dc current.

Nominal Value Value of Derating Factor K for Over or Under Current Ω Two-Wire Comp I

Specifications 1 1-13 DC Current Range Resolution Absolute Uncertainty ±5°C from calibration temperature For fields strengths >1 V/m but <3 V/m, add 1% of range Relative Uncertainty ±1°C 24 Hours 90 Days 180 Days 1 Year 24 Hours 90 Days nA ± (ppm output + nA) ± (ppm output + nA) 220 µA 2.2 mA 22 mA .1 1 10 45 + 10 45 + 10 45 + 100 50 + 10 50 + 10 50 + 100 55 + 10 55 + 10 55 + 100 60 + 10 60 + 10 60 + 100 24 + 2 24 + 5 24 + 50 26 + 2 26 + 5 26 + 50 µA ± (ppm output + µA) ± (ppm output + µA) 220 mA 2.2A [Note 1] .1 1 55 + 1 75 + 30 60 + 1 80 + 30 65 + 1 90 + 30 70 + 1 95 + 30 26 + .3 40 + 7 30 + .3 45 + 7 5725A Amplifier: 11A 10 330 + 470 340 + 480 350 + 480 360 + 480 100 + 130 110 + 130 Secondary Performance Specifications and Operating Characteristics Included in Uncertainty Specifications Temperature Coefficient [Note 2] Burden Voltage Maximum Load Noise Range Stability ±1°C 24 Hours 10°-40°C 0°-10°C and Compliance Limits Adder [Note 3] For Full Accuracy Bandwidth 0.1-10 Hz Bandwidth 10-10 kHz 40°-50°C [Note 4] pk-pk RMS V ± (ppm output + nA) ± (ppm output + nA)/°C ±nA/V Ω ppm output + nA nA 220 µA 2.2 mA 22 mA 220 mA 2.2A 5 + 1 5 + 5 5 + 50 8 + 300 9 + 7 µA 1 + .40 1 + 2 1 + 20 1 + 200 1 + 2.5 µΑ 3 + 1 3 + 10 3 + 100 3 + 1 µA A3 + 10 µA 10 10 10 10 3 [Note 5] .2 .2 10 100 2 µA 20k 2k 200 20 2 6 + .9 6 + 5 6 + 50 9 + 300 12 + 1.5 µA 10 10 50 500 20 µA 5725A: ± (ppm output + µA) ± (ppm output + µA)/°C ppm output + µA µA 11A 25 + 100 20 + 75 30 + 120 4 0 4 15 + 70 175 Notes: Maximum output from 5700A terminals is 2.2A. Uncertainty specifications for 220 µA and 2.2 mA ranges are increased by 1.3 X when supplied through 5725A terminals. Specifications are otherwise identical for all output locations. 1. Add to uncertainty specifications: ±200 X I 2 ppm for >100 mA on 220 mA range ±10 X I 2 ppm for >1A on 2.2A range 2. Temperature coefficient is an adder to uncertainty specifications. It does not apply unless operating more than ±5°C from calibration temperature. 3. Burden voltage adder is an adder to uncertainty specifications that does not apply unless burden voltage is greater than 0.5V. 4. For higher loads, multiply uncertainty specification by: 1 + 0.1 x actual load maximum load for full accuracy 5. 5700A compliance limit is 2V for outputs from 1A to 2.2A. 5725A Amplifier may be used in range-lock mode down to 0A. Minimum output: 0 for all ranges, including 5725A. Settling time to full accuracy: 1 second for µA and mA ranges; 3 seconds for 2.2A range; 6 seconds for 11A range; + 1 second for range or polarity change Overshoot: <5%

For fields strengths >1 V/m but <3 V/m, add 1% of range Relative Uncertainty ±1°C 24 Hours 90 Days 180 Days 1 Year 24 Hours 90 Days Hz ± (ppm output + nA) ± (ppm output + nA) 220 µA 1 nA 10-20 20-40 40-1k 1k-5k 5k-10k 650 + 30 350 + 25 120 + 20 500 + 50 .15% + 100 700 + 30 380 + 25 140 + 20 600 + 50 .16% + 100 750 + 30 410 + 25 150 + 20 650 + 50 .17% + 100 800 + 30 420 + 25 160 + 20 700 + 50 .18% + 100 450 + 30 270 + 25 110 + 20 450 + 50 .14% + 100 500 + 30 300 + 25 120 + 20 500 + 50 .15% + 100 2.2 mA 10 nA 10-20 20-40 40-1k 1k-5k 5k-10k 650 + 50 350 + 40 120 + 40 500 + 500 .15% + 1 µA 700 + 50 380 + 40 140 + 40 600 + 500 .16% + 1 µA 750 + 50 410 + 40 150 + 40 650 + 500 .17% + 1 µA 800 + 50 420 + 40 160 + 40 700 + 500 .18% + 1 µA 450 + 50 270 + 40 110 + 40 450 + 500 .14% + 1 µA 500 + 50 300 + 40 120 + 40 500 + 500 .15% + 1 µA 22 mA 100 nA 10-20 20-40 40-1k 1k-5k 5k-10k 650 + 500 350 + 400 120 + 400 500 + 5 µA .15% + 10 µA 700 + 500 380 + 400 140 + 400 600 + 5 µA .16% + 10 µA 750 + 500 410 + 400 150 + 400 650 + 5 µA .17% + 10 µA 800 + 500 420 + 400 160 + 400 700 + 5 µA .18% + 10 µA 450 + 500 270 + 400 110 + 400 450 + 5 µA .14% + 10 µA 500 + 500 300 + 400 120 + 400 500 + 5 µA .15% + 10 µA Hz ± (ppm output + µA) ± (ppm output + µA) 220 mA 1 µA 10-20 20-40 40-1k 1k-5k 5k-10k 650 + 5 350 + 4 120 + 4 500 + 50 .15% + 100 700 + 5 380 + 4 150 + 4 600 + 50 .16% + 100 750 + 5 410 + 4 170 + 4 650 + 50 .17% + 100 800 + 5 420 + 4 180 + 4 700 + 50 .18% + 100 450 + 5 280 + 4 110 + 4 450 + 50 .14% + 100 500 + 5 300 + 4 130 + 4 500 + 50 .15% + 100 2.2A 10 µA 20-1k 1k-5k 5k-10k 600 + 40 700 + 100 .80% + 200 650 + 40 750 + 100 .90% + 200 700 + 40 800 + 100 .95% + 200 750 + 40 850 + 100 1.0% + 200 600 + 40 650 + 100 .75% + 200 650 + 40 750 + 100 .85% + 200 5725A Amplifier: 11A 100 µA 40-1k 1k-5k 5k-10k 370 + 170 800 + 380 .3% + 750 400 + 170 850 + 380 .33% + 750 440 + 170 900 + 380 .35% + 750 460 + 170 950 + 380 .36% + 750 300 + 170 700 + 380 .28% + 750 330 + 170 800 + 380 .32% + 750

Specifications 1 1-15 AC Current (continued) Secondary Performance Specifications and Operating Characteristics Included in Uncertainty Specifications Range Frequency Stability ±1°C Temperature Coefficient [Note 1] Compliance Maximum Resistive Load Noise and Distortion 24 Hours 10°-40°C 0°-10°C and 40°-50°C Limits For Full Accuracy [Note 2] Bandwidth 10 Hz-50 kHz <0.5V Burden Hz ± (ppm output + nA) ± (ppm output + nA)/°C V rms Ω ± (% output + µA) 220 µA 10-20 20-40 40-1k 1k-5k 5k-10k 150 + 5 80 + 5 30 + 3 50 + 20 400 + 100 50 + 5 20 + 5 4 + .5 10 + 1 20 + 100 50 + 5 20 + 5 10 + .5 20 + 1 20 + 100 7 2k .05 + .1 .05 + .1 .05 + .1 .25 + .5 .5 + 1 2.2 mA 10-20 20-40 40-1k 1k-5k 5k-10k 150 + 5 80 + 5 30 + 3 50 + 20 400 + 100 50 + 5 20 + 4 4 + 1 10 + 100 50 + 400 50 + 5 20 + 4 10 + 2 20 + 100 50 + 400 7 500 .05 + .1 .05 + .1 .05 + .1 .25 + .5 .5 + 1 22 mA 10-20 20-40 40-1k 1k-5k 5k-10k 150 + 50 80 + 50 30 + 30 50 + 500 400 + 1 µA 50 + 10 20 + 10 4 + 10 10 + 500 50 + 1 µA 50 + 10 20 + 10 10 + 20 20 + 400 50 + 1 µA 7 150 .05 + .1 .05 + .1 .05 + .1 .25 + .5 .5 + 1 Hz ± (ppm output + µA) ± (ppm output + µA)/°C 220 mA 10-20 20-40 40-1k 1k-5k 5k-10k 150 + .5 80 + .5 30 + .3 50 + 3 400 + 5 50 + .05 20 + .05 4 + .1 10 + 2 50 + 5 50 + .05 20 + .05 10 + .1 20 + 2 50 + 5 7 15 .05 + 10 .05 + 10 .05 + 10 .25 + 50 .5 + 100 2.2A 20-1k 1k-5k 5k-10k 50 + 5 80 + 20 800 + 50 4 + 1 10 + 5 50 + 10 10 + 1 20 + 5 50 + 10 1.4 [Note 3] .5 .5 + 100 .3 + 500 1 + 1 mA 5725A Amplifier: ± (% output) 11A 40-1k 1k-5k 5k-10k 75 + 100 100 + 150 200 + 300 20 + 75 40 + 75 100 + 75 30 + 75 50 + 75 100 + 75 3 3 [Note 4] . . . 05 12 5    Notes: Maximum output from 5700A terminals is 2.2A. Uncertainty specifications for 220 µA and 2.2 mA ranges are increased by 1.3 x plus 2 µA when supplied through 5725A terminals. Specifications are otherwise identical for all output locations. 1. Temperature coefficient is an adder to uncertainty specifications that does not apply unless operating more than ±5°C from calibration temperature. 2. For larger resistive loads multiply uncertainty specifications by: ( actual load maximum load for full acuracy ) 2 3. 1.5V compliance limit above 1A. 5725A Amplifier may be used in range-lock mode down to 1A. 4. For resistive loads within rated compliance voltage limits. Minimum output:: 9 µA for 220 µA range, 10% on all other ranges. 1A minimum for 5725A. Inductive load limits: 400 µH (5700A or 5725A). 20 µH for 5700A output >1A. Power factors: 5700A, 0.9 to 1; 5725A, 0.1 to 1. Subject to compliance voltage limits. Frequency: Range (Hz): 10.000-11.999, 12.00-119.99, 120.0-1199.9, 1.200k-10.000k Uncertainty: ±0.01% Resolution: 11,999 counts Settling time to full accuracy: 5 seconds for 5700A ranges; 6 seconds for 5725A 11A range; +1 second for amplitude or frequency range change. Overshoot: <10%

Specifications apply to the end of the cable and 50Ω termination used for calibration: Range Absolute Uncertainty ±5°C from calibration temperature 30 Hz-500 kHz Volts dBm Resolution 24 Hours 90 Days 180 Days 1 Year ± (% output + µV) 1.1 mV -46 10 nV .4 + .4 .5 + .4 .6 + .4 .8 + 2 3 mV -37 10 nV .4 + 1 .45 + 1 .5 + 1 .7 + 3 11 mV -26 100 nV .2 + 4 .35 + 4 .5 + 4 .7 + 8 33 mV -17 100 nV .2 + 10 .3 + 10 .45 + 10 .6 + 16 110 mV -6.2 1 µV .2 + 40 .3 + 40 .45 + 40 .6 + 40 330 mV +3.4 1 µV 0.2 + 100 0.25 + 100 .35 + 100 .5 + 100 1.1V +14 10 µV .2 + 400 .25 + 400 .35 + 400 .5 + 400 3.5V +24 10 µV 15 + 500 .2 + 500 .3 + 500 .4 + 500 Frequency Frequency Resolution Amplitude Flatness, 1 kHz Reference Voltage Range Temperature Coefficient Settling Time To Full Accuracy Harmonic Distortion 1.1 mV 3 mV >3 mV Hz Hz ±% ±ppm/°C Seconds dB 10-30 .01 .3 .3 .3 100 7 -40 30-120 .01 .1 .1 .1 100 7 -40 120-1.2k .1 .1 .1 .1 100 5 -40 1.2k-12k 1 .1 .1 .1 100 5 -40 12k-120k 10 .1 .1 .1 100 5 -40 120k-1.2M 100 .2 + 3 µV .1 + 3 µV .1 + 3 µV 100 5 -40 1.2M-2M 100k .2 + 3 µV .1 + 3 µV .1 + 3 µV 100 0.5 -40 2M-10M 100k .4 + 3 µV .3 + 3 µV .2 + 3 µV 100 0.5 -40 10M-20M 1M .6 + 3 µV .5 + 3 µV .4 + 3 µV 150 0.5 -34 20M-30M 1M 1.5 + 15 µV 1.5 + 3 µV 1 + 3 µV 300 0.5 -34 Additional Operating Information: dBm reference = 50Ω Range boundaries are at voltage points, dBm levels are approximate. dBm = 10 log ( Power 1 mW ), 0.22361V across 50Ω = 1 mW or 0 dBm Minimum output: 300 µV (-57 dBm) Frequency uncertainty: ±0.01% Frequency resolution: 11,999 counts to 1.1999 MHz, 119 counts to 30 MHz. Overload protection: A short circuit on the wideband output will not result in damage. After settling time, normal operation is restored upon removal.

Specifications 1 1-17 General Specifications: Warm-Up time: 2 X the time since last warmed up, to a maximum of 30 minutes. System installation: Rear output configuration and rack- mount kit available. Standard interfaces: IEEE-488, RS-232, 5725A, 5205A or 5215A, 5220A, phase lock in (BNC), phase reference out (BNC). Temperature performance: Operating: 0°C to 50°C. Calibration: 15°C to 35°C. Storage: -40°C to 75°C. Relative humidity: Operating: <80% to 30°C, <70% to 40°C, <40% to 50°C. Storage: <95%, non-condensing. Safety: Designed to comply with UL1244 (1987); IEC 348-1978; IEC 66E (CO) 4; CSA 556B. Guard isolation: 20 volts EMI/RFI: Designed to comply with FCC Rules Part 15, Subpart J, Class B; VDE 0871, Class B. Reliability: MIL-T-28800D, para. 3.13.3. Line Power: 47 to 63 Hz; ±10% allowed about selectable nominal line voltage: 100V, 110V, 115V, 120V, 200V, 220V, 230V, 240V. Maximum power: 5700A, 300 VA; 5725A, 750 VA. Electromagnetic Compatibility: This instrument is designed to operate in Standards Laboratory environments where in electromagnetic is highly controlled. If used in areas with RF fields >0.78 V/m there could be errors in measurements. Size: 5700A: Height 17.8 cm (7 in), standard rack increment, plus 1.5 cm (0.6 in) for feet; Width 43.2 cm (17 in), standard rack width; Depth 63.0 cm (24.8 in), overall; 57.8 cm (22.7 in), rack depth. 5725A: Height 13.3 cm, (5.25 in); Width and depth same as 5700A. Both units project 5.1 cm, (2 in) from rack front. Weight: 5700A: 27 kg (62 lbs); 5725A: 32 kg (70 lbs). 43.2 cm (17 in) 17.8 cm (7 in) 63 cm (24.8 in) 6.35 cm (2.5 in) FOR CABLE ACCESS

2-2. Unpacking and Inspection.................................................................... 2-3 2-3. Service Information.............................................................................. 2-5 2-4. Placement and Rack Mounting............................................................. 2-5 2-5. Cooling Considerations........................................................................ 2-5 2-6. Connecting to the 5700A Calibrator .................................................... 2-6 2-7. Selecting Line Voltage......................................................................... 2-7 2-8. Accessing the Fuse............................................................................... 2-8 2-9. Connecting to Line Power.................................................................... 2-9

not touch the 5700A output terminals. Read this section before operating the 5725A. Introduction 2-1. This section provides instructions for unpacking and installing the 5725A. Procedures for line voltage selection, fuse replacement, and connection to line power and the 5700A Calibrator are provided here. Read this section before operating the 5725A. Instructions for connecting cables to a UUT (Unit Under Test) are in Section 4 of the 5700A Operator Manual. Unpacking and Inspection 2-2. The 5725A is shipped in a container that is specially designed to prevent damage during shipping. Inspect the 5725A carefully for damage, and immediately report any damage to the shipper. Instructions for inspection and claims are included in the shipping container. If you need to reship the 5725A, use the original container. If it is not available, you can order a new container from Fluke by identifying the amplifier’s model and serial number. When you unpack the 5725A, check for all the standard equipment listed in Table 2-1. Report any shortage to the place of purchase or to the nearest Technical Service Center. (A List of Technical Service Centers is located in Section 8 of this manual.) If performance tests are required for your acceptance procedures, refer to Section 3 of the 5700A Service Manual for instructions. Line power cords available from Fluke are listed in Table 2-2 and illustrated in Figure 2-1. Table 2-1. Standard Equipment Item Model or Part Number Amplifier 5725A Line Power Cord (See Table 2-2 and Figure 2-1) Shielded 5700A/5725A Interface Cable 842901 5725A Instruction Manual 823435 Spare 4A, 250V Fuse 216846 Certificate of Calibration (None)

TYPE VOLTAGE/CURRENT FLUKE OPTION NUMBER North America 120V/15A LC-1 North America 240V/15A LC-2 Universal Euro 220V/16A LC-3 United Kingdom 240V/13A LC-4 Switzerland 220V/10A LC-5 Australia 240V/10A LC-6 South Africa 240V/5A LC-7 LC-1 LC-2 LC-3 LC-4 LC-5 LC-6 LC-7 aq2f.eps Figure 2-1. Line Power Cords Available for Fluke Instruments

2-5 Service Information 2-3. Each 5725A Amplifier is warranted to the original purchaser for a period of one year beginning on the date received. The warranty is located at the front of this manual. Factory-authorized service and technical advice for the 5725A is available at Fluke Service Centers. Section 8 contains a list of Service Centers. Warning Servicing described in this manual is to be done by qualified service personnel only. To avoid electrical shock, do not service the 5725A unless you are qualified to do so. The owner may choose to repair a 5725A using the troubleshooting information in Section 7 to isolate a faulty module, then use the Module Exchange Program. Refer to the Fluke catalog or contact a Service Center representative for the module exchange procedure. Placement and Rack Mounting 2-4. You can stack the 5725A on top of or below the 5700A Calibrator. (Choose the configuration that provides the easiest access to the 5700A Calibrator controls.) Or, you can mount the 5725A in a standard-width, 24-inch (61-cm) deep equipment rack. For bench-top stacking, the 5725A is equipped with non-skid feet. To mount the 5725A in an equipment rack, order the accessory 5725A Rack Mount Kit, Model Y5735. An instruction sheet is packed with the kit. Caution Use only the rack mount slides included in the Y5735 kit. Rack mount slides intended for other instruments can block the side ventilation holes on the 5725A and cause overheating. Cooling Considerations 2-5. Caution Damage caused by overheating may occur if the area around the air intake is restricted, the intake air is too warm, or the fan filter becomes clogged. Accuracy and dependability of all internal parts of the 5725A are enhanced by maintaining the coolest possible internal temperature. By observing the following rules you can lengthen the life of the 5725A: • The area around the fan filter must be at least 3 inches from nearby walls or rack enclosures. • Exhaust perforations on the sides of the 5725A must be clear of obstructions. Most of the heat exits from the side vents near the front. • Air entering the instrument must be room temperature. Make sure that exhaust from another instrument is not directed into the fan inlet. • Clean the fan filter every 30 days, or more frequently if the 5725A is operated in a dusty environment. (Instructions for cleaning the fan filter are in Section 6.)

2-6. Proceed as follows to connect the 5725A to the 5700A: 1. Turn the power off for both instruments and disconnect their line power cords. 2. Connect either end of the interface cable to the 5725A connector labeled 5700A. Dress the cable only as Figure 2-2 shows. The figure shows how to dress the cable in installation arrangements with the 5725A on top or bottom. 3. Connect the other end to the 5700A connector labeled 5725A. The 5700A/5725A interface cable provides all the digital and analog control signals for the amplifier, and it provides conductors to route amplified voltage to the 5700A OUTPUT binding posts. 5700A 5725A 5700A 5725A 5725A AMPLIFIER 5700A CALIBRATOR 5700A CALIBRATOR 5725A AMPLIFIER aq3f.eps Figure 2-2. Correct Way to Dress Interface Cable

2-7 Selecting Line Voltage 2-7. The 5725A arrives from the factory configured for the line voltage normally appropriate for the country of purchase, or as specified at the time of purchase. Check the line power label on the rear panel of the 5725A to verify that the line voltage matches local line power. Figure 2-3 shows the location of the line power label and switches, and the switch settings for each line voltage. The 5725A can be set to operate from eight different nominal line voltages; each voltage setting has a voltage tolerance of ±10% and a frequency range of 47 to 63 Hz. The line voltage switches are located on the bottom left side of the rear panel. To change the line voltage setting, set the line voltage selection switches to the correct setting shown in Figure 2-3. 100V 110V 115V 120V S2 S3 S4 VOLTAGE SELECTION FUSE F8A 250V (FAST) 200V 220V 230V 240V S2 S3 S4 F4A 250V (FAST) JOHN FLUKE MFG. CO., INC. MADE IN U.S.A. PATENTS PENDING NO INTERNAL USER SERVICEABLE PARTS REFER SERVICE TO QUALIFIED SERVICE PERSONNEL TO CLEAN FILTER REMOVE FROM INSTRUMENT AND FLUSH WITH WARM SOAPY WATER 5700A CALIBRATOR 20V PK MAX CHASSIS GROUND FUSE WARNING GROUNDING CONNECTOR IN POWER CORD MUST BE CONNECTED TO ENSURE PROTECTION FROM ELECTRONIC SHOCK. 47-63 Hz 750VA MAX CAUTION FOR FIRE PROTECTION REPLACE ONLY WITH A 250V FUSE OF INDICATED RATING. S4 S3 S2 100V 110V 115V 120V S2 S3 S4 VOLTAGE SELECTION FUSE F8A 250V (FAST) 200V 220V 230V 240V S2 S3 S4 F4A 250V (FAST) CAUTION FOR FIRE PROTECTION REPLACE ONLY WITH A 250V FUSE OF INDICATED RATING. 11A MAX HI LO CALIBRATION ENABLE NORMAL CURRENT OUTPUT ! ! ! ! ! aq4f.eps Figure 2-3. Line Power Label and Switch Location

2-8. wCaution To prevent instrument damage, verify that the correct fuse is installed for the line voltage setting. Acceptable fuse types are Bussman type MTH or Littelfuse type 312 or equivalent, of the appropriate amperage rating. Use only a 4A, 250V fast-blow fuse when the line voltage selection switches are set in the range 200-240V. Note A spare 4A, 250V fuse is shipped with the 5725A to ensure that one is available for use on the 200-240V range. The line power fuse is accessible on the rear panel. The fuse rating label to the right of the fuse holder (labeled FUSE) shows the correct replacement fuse rating for each line voltage setting. To check or replace the fuse, refer to Figure 2-4 and proceed as follows: 1. Turn off the POWER switch and disconnect the line power cord from ac line power. 2. Insert the blade of a standard screwdriver in the slot of the fuse holder labeled FUSE. 3. Turn the screwdriver counterclockwise until the cap and fuse pop free. 4. To reinstall the fuse, reverse this procedure. 100V 110V 115V 120V S2 S3 S4 VOLTAGE SELECTION FUSE F8A 250V (FAST) 200V 220V 230V 240V S2 S3 S4 F4A 250V (FAST) JOHN FLUKE MFG. CO., INC. MADE IN U.S.A. PATENTS PENDING NO INTERNAL USER SERVICEABLE PARTS REFER SERVICE TO QUALIFIED SERVICE PERSONNEL TO CLEAN FILTER REMOVE FROM INSTRUMENT AND FLUSH WITH WARM SOAPY WATER 5700A CALIBRATOR 20V PK MAX CHASSIS GROUND FUSE WARNING GROUNDING CONNECTOR IN POWER CORD MUST BE CONNECTED TO ENSURE PROTECTION FROM ELECTRONIC SHOCK. 47-63 Hz 750VA MAX CAUTION FOR FIRE PROTECTION REPLACE ONLY WITH A 250V FUSE OF INDICATED RATING. S4 S3 S2 11A MAX HI LO CALIBRATION ENABLE NORMAL CURRENT OUTPUT ! ! ! aq5f.eps Figure 2-4. Accessing the Fuse

2-9 Connecting to Line Power 2-9. Warning To avoid shock hazard, connect the factory-supplied, three- conductor line power cord to a properly grounded power outlet. Do not use a two-conductor adapter or extension cord; this will break the protective ground connection. After verifying that the line voltage selection switches are correctly set, verify that the correct fuse is installed. Connect the 5725A to a properly grounded three-prong outlet.

3-2. Front Panel Features............................................................................. 3-4 3-3. Rear Panel Features.............................................................................. 3-6 3-4. Turning on the 5725A Amplifier.......................................................... 3-8 3-5. Warm Up .............................................................................................. 3-8 3-6. 5725A Operating Functions and Modes............................................... 3-9 3-7. Standby............................................................................................. 3-9 3-8. Voltage Standby............................................................................... 3-10 3-9. Current Standby ............................................................................... 3-11 3-10. Voltage Operate ............................................................................... 3-12 3-11. Current Operate................................................................................ 3-13 3-12. Conditions That Activate the 5725A.................................................... 3-14

section begins with a reference for the 5725A front and rear panel features. Information about setting up and powering up the 5725A follows. Please read this information before operating the amplifier. Also contained in this section is a description of all 5725A operating functions and modes. Because the amplifier operates under complete control of the 5700A Calibrator, operating instructions such as how to call up a specific output value are contained in Section 4 of the 5700A Operator Manual. Operating the 5725A in remote control is covered in Section 5 of the 5700A Operator Manual.

3-2. Front panel features are called out in Figure 3-1. Each front panel feature is described in Table 3-1. CURRENT OUTPUT HI LO VOLTAGE MODE CURRENT MODE 5725A STANDBY FAULT OVERLOAD CABLE OFF POWER 1 2 3 4 5 6 7 8 11A MAX 2OV PK MAX aq6f.eps Figure 3-1. Front Panel Features

3-5 Table 3-1. Front Panel Features A CURRENT OUTPUT Binding Posts The source of all amplified current if the 5725A is configured for front output. You can set the 5700A to source all unamplified as well as amplified current through these binding posts. The LO binding post is isolated from ground when in the current function, and is open-circuited at other times. Cable and connection recommendations are made in Section 4 of the 5700A Operator Manual. B 5725A STANDBY Indicator Lit whenever the 5725A is in any of three standby modes. This indicator is lit alone in standby mode; it is lit at the same time as VOLTAGE MODE in voltage standby mode; and it is lit at the same time as CURRENT MODE in current standby mode. (See "5725A Operating Functions and Modes," further on in this section.) C CURRENT MODE Indicator Lit when the 5725A is in current standby or current operate mode. In current standby mode, the STANDBY indicator is also lit. (See "5725A Operating Functions and Modes," further on in this section.) D VOLTAGE MODE Indicator Lit when the 5725A is in voltage standby or voltage operate mode. In voltage standby mode, the STANDBY indicator is also lit. (See "5725A Operating Functions and Modes," further on in this section.) E POWER Switch Turns the power on and off. The switch is a push-push type; the first push turns the power on and locks the switch in, and the second push turns the power off and releases the switch. F CABLE OFF Indicator Lit when the 5700A/5725A interface cable is not connected, or when the 5700A power is turned off. This condition also lights the FAULT indicator. G OVERLOAD Indicator Lights on entering current operate mode in overcompliance conditions (load not connected to the proper binding posts, or load resistance too high). The OVERLOAD indicator also lights on entering voltage operate mode if the load resistance is too low. H FAULT Indicator Lit whenever any fault condition is detected. Normally, a fault code and message appears on the 5700A Control Display when this happens. The FAULT indicator also comes on with the CABLE OFF indicator when the 5700A/5725A interface cable is not connected. In case of a FAULT indication, check the 5700A/5725A interface cable connections, make sure the 5700A power is on, and check that the load is appropriate and connected to the correct binding posts. Refer to "Service Information" in Section 2, or to Section 7, Troubleshooting, in case of a FAULT indication that appears to be a malfunction.

3-3. Rear panel features are called out in Figure 3-2. Each rear panel feature is briefly described in Table 3-2. 1 2 3 4 5 6 7 8 100V 110V 115V 120V S2 S3 S4 VOLTAGE SELECTION FUSE F8A 250V (FAST) 200V 220V 230V 240V S2 S3 S4 F4A 250V (FAST) JOHN FLUKE MFG. CO., INC. MADE IN U.S.A. PATENTS PENDING NO INTERNAL USER SERVICEABLE PARTS REFER SERVICE TO QUALIFIED SERVICE PERSONNEL TO CLEAN FILTER REMOVE FROM INSTRUMENT AND FLUSH WITH WARM SOAPY WATER 5700A CALIBRATOR 20V PK MAX CHASSIS GROUND FUSE WARNING GROUNDING CONNECTOR IN POWER CORD MUST BE CONNECTED TO ENSURE PROTECTION FROM ELECTRONIC SHOCK. 47-63 Hz 750VA MAX CAUTION FOR FIRE PROTECTION REPLACE ONLY WITH A 250V FUSE OF INDICATED RATING. S4 S3 S2 11A MAX HI LO CALIBRATION ENABLE NORMAL CURRENT OUTPUT ! ! ! 9 aq7f.eps Figure 3-2. Rear Panel Features

3-7 Table 3-2. Rear Panel Features A CURRENT OUTPUT Binding Posts The source of all amplified current if the 5725A is configured for rear output. You can set the 5700A to source all its unamplified as well as amplified current through these binding posts. The LO binding post is isolated from ground when in the current function, and is open-circuited at other times. Cable and connection recommendations are made in Section 4 of the 5700A Operator Manual. B CALIBRATION Switch A slide switch that enables and disables writing to the nonvolatile memory that stores 5725A calibration constants. Switching to ENABLE allows writing to the memory, and switching to NORMAL protects data in memory from being overwritten. The switch must be in the ENABLE position to store corrections generated during calibration. The switch is recessed to allow a metrologist to cover it with a calibration seal to guarantee calibrator integrity. C 5700A CALIBRATOR Connector Provides the analog and digital interface to the 5700A Calibrator. After connecting to the 5700A, you control the 5725A from the 5700A front panel or by sending remote commands to the 5700A. Refer to "Using an Auxiliary Amplifier" in Section 4, or for remote operation to Section 5, of the 5700A Operator Manual for details. D Fan Filter Covers the air intake to keep dust and debris out of the instrument. The fan directs a constant cooling air flow throughout the chassis. E Line Voltage/Fuse Rating Label Shows the various settings of the line voltage switches, and the correct replacement fuse for operating voltages of 110 (90 to 132) and 220 (180 to 264) volts ac. Refer to "Accessing the Fuse" in Section 2 for the fuse replacement procedure. F Line Voltage Selection Switches Select the operating line voltage. Refer to "Selecting Line Voltage" in Section 2 for instructions on how to select operating line voltage. G Fuse Holder The line power fuse. Refer to "Accessing the Fuse" in Section 2 for fuse rating information and the fuse replacement procedure. H CHASSIS GROUND Connector If the 5725A is the location of the ground reference point in a system, the CHASSIS GROUND binding post can be used for connecting other instruments to earth ground. (The chassis is connected to earth ground through the three-conductor line cord.) I Line Power Input A grounded male three-prong connector that accepts the line power cord.

3-4. Warning To avoid electric shock, make sure the 5725A is safely grounded as described in section 2. Caution Before turning the 5725A on, make sure that the line voltage selection switches are set properly for your line voltage. Refer to Figure 2-3 or the line voltage switch label and check the line voltage setting now if you have not already done so. When you turn on the 5725A, all six front panel indicators light briefly and the 5725A undergoes a self test. If the self test fails, a fault message on the 5700A Control Display identifies the failure, indicating that you should service the 5725A. After the 5725A passes its self test, it transfers its calibration constants to the 5700A. During the transfer, the BOOST indicator on the 5700A flashes. For the few seconds that the BOOST indicator is flashing, the 5725A is not usable. After the transfer is complete, the 5725A is in standby mode. (See "5725A Operating Functions and Modes" for more information about standby mode.) Warm Up 3-5. When you turn on a cold 5725A, warm it up for 30 minutes to allow the components inside to stabilize. This ensures that the 5725A meets or exceeds the specifications listed in Section 1. If you turn off the 5725A after it has warmed up, allow it to warm up again for at least twice the length of time it was turned off (up to a maximum of 30 minutes of warm-up). For example, if the 5725A is turned off for 10 minutes, allow it to warm up again for at least 20 minutes.

3-9 5725A Operating Functions and Modes 3-6. Warning Both the 5700A and 5725A can produce fatal voltages. boosted voltage operation produces high voltage at higher current levels than normally available from the 5700A. during 5725A voltage operation, the potential risk of injury or fatal accident is greater than during unamplified 5700A voltage operation. The 5725A has five normal modes of operation, including active output in its three output functions: ac voltage, dc current, and ac current. The five normal operating modes are: • Standby (also referred to as "dormant" on the schematics) • Voltage Standby • Current Standby • Voltage Operate • Current Operate Each normal operating mode is described in the following paragraphs. For the meaning of FAULT, OVERLOAD, or CABLE OFF indications, refer to Table 3-1. Standby 3-7. CURRENT OUTPUT HI LO VOLTAGE MODE CURRENT MODE 5725A STANDBY FAULT OVERLOAD CABLE OFF 11A MAX 2OV PK MAX NO OUTPUT HI HI LO LO AUX CURRENT GUARD GROUND WIDEBAND SENSE V A Ω OUTPUT V A Ω EX SNS EX GRD BOOST µ m k 9 8 7 5 6 M 3 0 • 2 1 OPR STBY W BND 4 +/- NO OUTPUT HI BOOST OFF aq8i.eps Standby mode is when only the 5725A STANDBY indicator is lit. In standby mode, the 5725A is not supplying an output. However, the 5700A, depending on how it is set, can be supplying up to 1100V or 2.2A. Standby occurs under any of the following conditions: • At power-up with no pending 5725A entry on the 5700A. • When the 5725A is not selected in a 5700A setup menu as the amplifier for the 5700A output function in use, and the 5725A is not selected as the output location for all 5700A current.

indicators are lit. In voltage standby mode, the 5725A is not supplying an output. Voltage standby occurs if "5725A" is selected in a 5700A setup menu as the voltage amplifier, and the next two conditions are true: • An ac voltage 220V or above is showing on the 5700A Output Display with the STANDBY annunciator lit. • The BOOST indicator on the 5700A is lit. Note If condition 1 is true, the BOOST indicator can be toggled on and off by pressing the 5700A BOOST key. If the BOOST indicator is off, the 5725A is in standby mode, not voltage standby.

3-11 Current Standby 3-9. CURRENT OUTPUT HI LO VOLTAGE MODE CURRENT MODE 5725A STANDBY FAULT OVERLOAD CABLE OFF 11A MAX 2OV PK MAX NO OUTPUT HI HI LO LO AUX CURRENT GUARD GROUND WIDEBAND SENSE V A Ω OUTPUT V A Ω µ • NO OUTPUT HI BOOST LIT aq10i.eps Current standby mode is when both CURRENT MODE and 5725A STANDBY indicators are lit. In current standby mode, the 5725A is not supplying an output. Current standby occurs under any of the following conditions: • When the 5700A current output location is set to "5725A", and any ac or dc current level is showing on the 5700A Output Display with the STANDBY annunciator lit. • If "5725A" is selected in a 5700A setup menu as the current amplifier, and any of the following conditions are true: 1. An ac or dc current 2.2A or above is showing on the 5700A Output Display with the STANDBY annunciator lit. 2. Any level of dc current is showing on the 5700A Output Display with the STANDBY annunciator lit, and the BOOST key on the 5700A is pressed so that the BOOST indicator is lit. 3. An ac current 1A or above is showing on the 5700A Output Display with the STANDBY annunciator lit, and the BOOST key on the 5700A is pressed so that the BOOST indicator is lit. 4. The 5700A is ranged locked on the 11A range, and any dc current or an ac current 1A or above is showing on the Output Display with the STANDBY annunciator lit.

voltage operation produces high voltage at higher current levels than normally available from the 5700A. during voltage operation, the potential risk of injury or fatal accident is greater than during normal operation. Voltage operate mode is when only the VOLTAGE MODE indicator is lit. In voltage operate mode, amplified voltage output is available at the 5700A binding posts. Voltage operate occurs if "5725A" is selected in a 5700A setup menu as the voltage amplifier, and the next two conditions are true: • An ac voltage 220V or above is showing on the 5700A Output Display with the OPERATE annunciator lit. • The BOOST indicator on the 5700A is lit. Note If condition 1 is true, the BOOST indicator can be toggled on and off by pressing the 5700A BOOST key. If the BOOST indicator is off, then the 5725A is in standby mode. Note Under certain settings of ac voltage, especially high voltage between 1 to 5 kHz, a whine from the 5725A is audible. This originates from the output transformer, and is normal.

3-13 Current Operate 3-11. CURRENT OUTPUT HI LO VOLTAGE MODE CURRENT MODE 5725A STANDBY FAULT OVERLOAD CABLE OFF 11A MAX 2OV PK MAX CURRENT OUTPUT HERE HI HI LO LO AUX CURRENT GUARD GROUND WIDEBAND SENSE V A Ω OUTPUT V A Ω µ • NO OUTPUT HI BOOST LIT aq12i.eps Note An overcompliance fault occurs if a low-resistance load is not connected to the enabled 5725A binding posts when entering current operate mode. Current operate mode is when only the CURRENT MODE indicator is lit. In current operate mode, current output (either 5725A amplified current or redirected 5700A current) is available at the 5725A binding posts. Current operate occurs under the following conditions: • When, on the 5700A, the current output location is set to "5725A", and any ac or dc current level is showing on the 5700A Output Display with the OPERATE annunciator lit. • If "5725A" is selected in a 5700A setup menu as the current amplifier, and any of the following conditions are true: 1. An ac or dc current 2.2A or above is showing on the 5700A Output Display with the OPERATE annunciator lit. 2. Any level of dc current is showing on the 5700A Output Display with the OPERATE annunciator lit, and the BOOST key on the 5700A is pressed so that the BOOST indicator is lit. 3. An ac current 1A or above is showing on the 5700A Output Display with the OPERATE annunciator lit, and the BOOST key on the 5700A is pressed so that the BOOST indicator is lit. 4. The 5700A is ranged locked on the 11A range, and any dc current or an ac current 1A or above is showing on the Output Display with the OPERATE annunciator lit. Note Under certain settings of ac current, especially high current at frequencies above 1 kHz, a whine from the 5725A is audible. This is caused by a piezo effect in the current output transistors, and is normal.

3-12. When the 5725A is connected to the 5700A, and is selected as the amplifier for the active output function, it supplies an output under the conditions shown in the following list. (These conditions are the same as VOLTAGE OPERATE and CURRENT OPERATE as previously described.) • Whenever current above 2.2A is selected and the 5700A is set to operate. (Output available at the 5725A binding posts.) • Whenever ac voltage in the 220-1100V range is selected and the 5700A is set to operate. Note that the 5725A takes over the 1100V ac range of the 5700A if the 5725A is selected as the voltage amplifier in a setup menu. (Output available at the 5700A binding posts.) • Whenever the 5700A BOOST key is toggled on while the 5700A output setting is in the operating range of the 5725A, voltage or current. (Output location is 5725A for current, 5700A for voltage.) • If the "Range" softkey is set to "LOCKED" while supplying a current greater than 2.2A, then the 5725A stays active if the 5700A output setting is adjusted down to 0A dc, or down to 1A ac. (Output available at the 5725A binding posts.) Regardless of the "BOOST AMP TYPES" setting in the 5700A setup menus, all unamplified 5700A current is supplied through the 5725A binding posts when, on the 5700A, the current output location is set to "5725A"; the 5700A output is set to any ac or dc current level; and the 5700A OPERATE annunciator is lit.

Title Page 4-1. Introduction .......................................................................................... 4-3 4-2. Overall Functional Description............................................................ 4-3 4-3. 1100V AC Range Functional Description ....................................... 4-5 4-4. 11A Range Functional Description.................................................. 4-6 4-5. Operation in the 11A DC Range.................................................. 4-7 4-6. Operation in the 11A AC Range.................................................. 4-7 4-7. Voltage and Current Standby Modes............................................... 4-7 4-8. Voltage Standby........................................................................... 4-7 4-9. Current Standby........................................................................... 4-7 4-10. How the 5700A and 5725A Communicate ...................................... 4-8 4-11. Description of the Out-Guard Lines (5725A Side) ..................... 4-8 4-12. Description of the In-Guard Lines............................................... 4-9 4-13. Functional Summaries by Assembly................................................ 4-10 4-14. Detailed Circuit Description ................................................................ 4-11 4-15. Interconnect Assembly (A1) ............................................................ 4-11 4-16. Power Supply Assembly (A4).......................................................... 4-12 4-17. High Voltage Supply Section ...................................................... 4-13 4-18. Switching Section........................................................................ 4-14 4-19. Current-Limit Section.................................................................. 4-15 4-20. System Supply Section ................................................................ 4-15 4-21. Fan Supply Section...................................................................... 4-16 4-22. Digital Assembly (A5)..................................................................... 4-16 4-23. Microcomputer ............................................................................ 4-16 4-24. External RAM.............................................................................. 4-16 4-25. External ROM.............................................................................. 4-16 4-26. EEROM ....................................................................................... 4-18 4-27. Data Latch.................................................................................... 4-18 4-28. Strobe Lines................................................................................. 4-18 4-29. Led Driver.................................................................................... 4-18

4-31. Break-Detect Circuitry................................................................. 4-19 4-32. Power Up and Reset Circuitry..................................................... 4-19 4-33. Watchdog Timer.......................................................................... 4-19 4-34. Current Amplifier Assembly (A2) ................................................... 4-19 4-35. Error Amplifier Section............................................................... 4-21 4-36. Output Stage Section ................................................................... 4-22 4-37. Monitor Section........................................................................... 4-22 4-38. Control and Switching Section.................................................... 4-23 4-39. Power Supply Section.................................................................. 4-23 4-40. High Voltage Amplifier (A3)........................................................... 4-24 4-41. Input Amplifier ............................................................................ 4-24 4-42. Integrator...................................................................................... 4-26 4-43. Window Comparator ................................................................... 4-26 4-44. Input Clamp ................................................................................. 4-26 4-45. Transconductance and Cascode Stage......................................... 4-27 4-46. Midstage ...................................................................................... 4-27 4-47. Midstage -400V Filter ................................................................. 4-27 4-48. High Voltage Heat Sink Assemblies ........................................... 4-27 4-49. Autobias Current Source ............................................................. 4-28 4-50. Autobias Sense Circuit ................................................................ 4-28 4-51. High Voltage Amplifier Feedback............................................... 4-29 4-52. Signal Transformers .................................................................... 4-29 4-53. Temperature Monitoring.............................................................. 4-29 4-54. High Voltage Sense Assembly (A6) ................................................ 4-30 4-55. Sense Amplifier Section .............................................................. 4-32 4-56. Analog Monitor Section .............................................................. 4-34 4-57. Serial Interface/Guard Crossing Section ..................................... 4-35 4-58. Analog Input Switching Section.................................................. 4-35 4-59 Control Section............................................................................ 4-36 4-60. AC Line Voltage Selection Section............................................. 4-37

Introduction 4 4-3 Introduction 4-1. This section presents theory of operation in increasing level of detail. The 5725A Amplifier is first broadly defined in an overall functional description and block diagram. The overall functional description continues in more detail with functional descriptions by function (ac V, dc I, ac I, and standby). The overall picture is completed with a detailed discussion of how the 5700A and 5725A communicate. The largest part of this section is devoted to detailed component-level circuit descriptions, grouped by assembly. Warning Lethal voltage (±500V) appears on the internal heat sink assemblies, and at many other points inside the 5725A chassis. Do not open the 5725A cover without referring to the access procedures and warnings in section 6. Theory text in this section is here strictly for the purpose of describing how circuits work, and contains no access procedures. Overall Functional Description 4-2. The 5725A provides three primary functions for the 5700A Calibrator: • Extended frequency range for high ac voltage • High-range dc current • High-range ac current The 5725A also has a secondary function of sourcing all 5700A current outputs (without the 5700A Current guard) through its own binding posts, if so selected at the 5700A front panel controls. Refer to Figure 4-1, the overall block diagram of the 5725A, for this discussion. Each 5725A function is described briefly next. • 1100V AC Function: The 1100V ac function can output 220 to 1100V, 40 Hz to 30 kHz; and 220 to 750V, 30 kHz to 100 kHz. The 1100V ac function is implemented with a gain of -100 amplifier. Input for the ac voltage function comes from the 5700A Oscillator, spanning the range of 2.2 to 11V. The 5725A returns an oscillator sense voltage of precisely -1/100 of the output voltage to the 5700A. Voltage outputs go through the 5725A/5700A interconnect cable to either the 5700A front or rear panel OUTPUT binding posts.

Overall Functional Description 4 4-5 • 11A DC Function: The 11A dc function is implemented with a transconductance (voltage in/current out) amplifier with a gain of -5. If the 5700A outputs -2V into the 5725A, the 5725A output is 10A. (This is transparent to the user.) The output range is 0 to 11A. The 5725A delivers amplified current to either the front or rear panel binding posts of the 5725A, depending on an internal hardware setup. Reconfiguration requires removing the covers, and is described in Section 6. • 11A AC Function The 11A ac function is similar to the 11A dc function. The frequency range is 40 Hz to 10 kHz. The output range is 1 to 11A rms. As in the dc current function, all outputs from the 5725A either go through the front or rear panel of the 5725A. Input to the 5725A comes from the 5700A Oscillator assembly. 1100V AC Range Functional Description 4-3. The 5700A Oscillator assembly generates the driving ac voltage, then sends it to the 5725A Power Amplifier for amplification. The 5725A returns an attenuated feedback voltage for output correction. The final output voltage is kept accurate by the high voltage sense amplifier and a real-time, software-controlled feedback loop within the 5700A, incorporating a 5700A ac/dc thermal rms converter. The 5700A Oscillator, DAC (digital-to-analog converter), and ac/dc thermal rms converter work together with the 5725A Power Amplifier and high voltage attenuator circuits to produce the desired output. Active assemblies in the 5725A ac voltage function are as follows: • In the 5700A: CPU, DAC, Oscillator, Oscillator Control, High-Resolution Oscillator, Switch Matrix, Motherboard, Rear Panel assemblies. • In the 5725A: CPU, High Voltage Amplifier, High Voltage Sense, Signal Transformer, Power Supply, Digital, and Interconnect assemblies. When an ac voltage in the 220 to 1100V range is selected, the 5700A calls the 5725A amplifier and leaves its own high voltage amplifier dormant. The 5725A takes over the 1100V ac range automatically. The 5725A produces ac voltage in the following sequence: 1. The 5700A sets the Oscillator assembly to the proper frequency and amplitude. The 5700A sets the initial amplitude using an 8-bit resistive hybrid dac located on the Oscillator amplifier assembly, yielding an Oscillator output accuracy of about 0.5%. 2. Next, the 5725A Power Amplifier amplifies this signal by -100 and returns an accurately attenuated signal to the 5700A. 3. The 5700A thermal sensor and adc (analog-to-digital converter) monitoring system fine tune the Oscillator amplitude. The DAC assembly output is switched directly to the Oscillator assembly, controlling the dac output amplitude. AC voltage calibration constants stored in the 5725A determine the 5700A DAC voltage setting.

1. An rms thermal sensor alternately measures two signals: an unknown but adjustable ac signal, and a known calibrated dc signal. 2. The output of the thermal sensor is measured by the adc, allowing settling time for the sensor each time its input is changed. The ac signal is adjusted until the thermal sensor output is the same for both signals. Thus, the dc voltage at the output of the thermal sensor is not important, but differences in the dc voltage when the sensor input is switched between the ac variable and dc reference are important. To ensure safe, reliable operation, the High Voltage Amplifier is turned on in the following sequence: 1. The 5700A Oscillator is set to the 22V range and its output is channeled to the 5725A High Voltage Amplifier on line BOOST IN. 2. Then the output of the High Voltage Amplifier is connected to the appropriate high voltage step-up transformer (one of three). 11A Range Functional Description 4-4. The 5725A Current Amplifier is a transconductance amplifier that has a compliance voltage of 3.0V rms for the ac current function and 4.0V for the dc current function. The transconductance amplifier has a gain of -5 (e.g., 1V in gives -5A out). Either the 5700A 2V range for dc operation, or the Oscillator for ac operation, drives the transconductance amplifier. Input voltage to the transconductance amplifier comes in on BOOST IN (for ac current) or B-FEEDBACK (for dc current) and enters the High Voltage Sense assembly. From there it is routed to the error amplifier on the Current assembly whenever the 5725A is in the current function. The B-FEEDBACK line returns the current calibration amplifier output to OSC SENSE HI during ac current operation. The following assemblies are active in the 5725A current function: • In the 5700A: CPU, DAC, Oscillator, Switch Matrix, Motherboard, Rear Panel assemblies. (Plus the Oscillator assembly in the ac current function.) • In the 5725A: CPU, Current, High Voltage Sense, Digital, and Power Supply.

Overall Functional Description 4 4-7 Operation in the 11A DC Range 4-5. For the dc current function, the 5700A is configured for the dc 2.2V range. The 5700A 2V dc range drives an error amplifier with an input impedance of 40 kΩ. The gain of this amplifier is determined by this 40 kΩ resistor with a 4 kΩ feedback resistor, and the value of the precision shunt. The 5725A uses a 0.02Ω shunt for the 11A function. There is no feedback to the 5700A. The 5725A monitors the error amplifier output voltage using the 16-channel multiplexer. One channel of the multiplexer, ICOMPL M, is scanned every 30 milliseconds or faster, with its output compared to -2V from the DAC. If the peak error amplifier output is more negative than the dac voltage, MONCOMP goes LOW and is read by bit 6 of port 5 of U507, the CPU. This indicates an overload condition, and lights the OVERLOAD LED. If a later scan shows the same result, the CPU trips the Current Amplifier into standby and reports this condition to the 5700A. A soft-start from standby to operate transitions reduces sudden current changes. This allows the 5725A to drive inductive loads such as power meters and clamp-on type current probes. Operation in the 11A AC Range 4-6. For ac current operation, input to the 5725A comes from the 5700A Oscillator. The 5700A Oscillator is configured for the 2.2V ac range, with sensing back to the 5700A Oscillator coming from the current shunt through the calibration amplifier circuit (on the Current Assembly). Voltage and Current Standby Modes 4-7. When a change in output function is selected, the 5725A goes through voltage or current standby mode before connecting the output to the 5725A binding posts, or to the 5700A. Voltage or current standby allows for local sensing within the 5725A, and for establishment of a known input condition in current and ac voltage. Voltage Standby 4-8. In voltage standby, the 5700A binding posts are completely disconnected from the rest of the instrument circuitry, and the 5725A high voltage output and sense lines (B-OUT HI and B-SENSE HI) are disconnected from the 5725A/5700A connector. The High Voltage Amplifier remains powered from the high voltage supply, but its input is grounded by pulling CLAMPD, and its output (MV OUT) is disconnected from the output transformers. Analog monitor circuitry continues to check the voltage and current on the high voltage supplies as well as the heat sink temperatures and cable integrity. It prevents the 5725A from switching to operate if a fault is present. Current Standby 4-9. In current standby, the binding posts are disconnected from the instrument circuitry, but all 5725A/5700A connections are made as in the operate mode. In dc current standby, the 5700A DAC supplies a voltage that corresponds to the dc current selected. In ac current standby, 5725A relay settings are identical to those for dc current standby. The 5700A Oscillator supplies an ac voltage level that corresponds to the selected output current and frequency.

4-10. The 5725A and 5700A maintain all analog and digital communication over an external cable connected to subminiature D-type connectors on the back of each instrument. All in-guard (analog) signals, except B-VGRD, connect to relays that isolate the 5725A and 5700A whenever the 5725A is not in use. Digital communication occurs over five out-guard (digital) 5700A lines, B-SCT, B-SCR, B+5V, B+5VCOM, and B-CINT*. The B+5V and B+5VCOM lines power the 5725A guard crossing and allow the 5725A to detect when the cable is disconnected. Lines B- SCT and B-SCR provide serial communication of data over an RS-232 type line. Optoisolators on the 5725A maintain the integrity of the guard. Line B-CINT* is a hardwire loop that allows the 5700A to detect a cable off or 5725A power off condition. Description of the Out-Guard Lines (5725A Side) 4-11. The following list describes the five 5725A out-guard lines: • B-RCV (Serial Communication Receive) Receives serial data from the 5700A; connects to the B-SCT line of the 5700A. • B-XMIT (Serial Communication Transmit) Transmits serial data to the 5700A; connects to the B-SCR line of the 5700A. • B+5V 5700A out-guard supply that powers optoisolators and 5725A CABLEOFF relay. • B+5VCOM 5700A out-guard supply common for above. • B-CINT* (Boost Cable Interlock) Hardwire "loop around system" on the 5725A that is polled at least every 100 ms by the 5700A to determine if the 5700A/5725A cable is connected and if the 5725A is turned on. Returns a low to the 5700A if above is true. A pull-up resistor on the 5700A leaves this line high if the interconnect cable is open or if the 5725A is turned off.

Overall Functional Description 4 4-9 Description of the In-Guard Lines 4-12. The following list describes the 11 5725A in-guard lines: • B-RCL High-quality analog line from the 5725A which carries critical signals to be measured by the 5700A adc during either 5725A calibration or 5725A self diagnostics. During calibration, these signals are ICAL (output of the current calibration amplifier), HVSENSE (DC output of the sense amplifier during dc gain ac characterization), AC/AC (buffered output of the 5725A thermal rms sensor that does frequency characterization). • B-OUT HI High voltage output from the 5725A step-up transformers, to be routed to either the 5700A front or rear panel terminals. • B-SENSE HI High voltage sense line from the 5700A output terminals. This signal is then attenuated -100:1 by the High Voltage Sense assembly. • BOOST IN During normal 5725A ac operation, carries the 5700A DAC outputs, which in turn drives either the High Voltage Amplifier or Current Amplifier. During 5725A calibration, BOOST IN drives the High Voltage Sense assembly with up to -260V from the 5700A Power Amplifier. • B-CURRENT Analog line that carries the current high output from the 5700A. When the user sets the current output location to "5725A" in a 5700A menu, this signal is routed to the 5725A binding posts. Under this operating condition, all 5700A/5725A current ranges are available from the same binding posts. Line B-CURRENT carries up to 2.2A in normal operation. During current calibration, this line carries 1.3A to measure the value of the 0.02Ω 5725A current shunt. • B-IRTN Current return for B-CURRENT; carries up to 2.2A. Line B-IRTN eventually ties to the same node as SCOM on the 5700A. • B-IGRD Current guard voltage from the 5700A; enables internal guarding within the 5725A only. • B-VGRD 5700A guard. Enables discrete guarding/shielding within the 5725A. • B-PACOM System common from the 5700A. Once inside the 5725A, it becomes VCOM, HVCOM, DCOM, and KCOM. B-PACOM is the current return for signals from the 5700A, including source current for driving the 5725A in the ac voltage function. Current output from the 5700A, when "5725A" is selected as the current output location, returns via B-IRTN. • B-SENSE LO High quality ground from the 5700A that is the reference point for the 5700A DAC and Oscillator assemblies.

voltage called MCOM. • B-FEEDBACK During ac voltage operation, B-FEEDBACK is the output of the High Voltage Sense assembly; this signal represents B-SENSE HI divided by -100, and drives the 5700A ac/dc thermal sensor. During low-frequency ac voltage calibration, this is the sense path for the -260V dc from the 5700A Power Amplifier. During ac current operation, B-FEEDBACK is the output of the current calibration amplifier. It represents the output current divided by -5 and drives the 5700A Oscillator feedback. During dc current operation, voltage from the 5700A 2V dc range is fed to the 5725A on B-FEEDBACK. If B-FEEDBACK is out of tolerance during 5725A ac voltage or current operation but no other faults are reported, the 5700A sends a message to the 5725A asking for a sequenced shutdown into standby, and displays a fault message on its Control Display. The 5725A FAULT indicator lights. A faulty 5700A/5725A interface connection could cause this problem. Functional Summaries by Assembly 4-13. For an overview of all the assemblies in the 5725A and the functions contained on each, refer to Figure 4-1, the overall block diagram, and the following list: • Interconnect Assembly (A1): • Connectors and traces to link other assemblies and fan • High voltage transformer secondary switching circuitry • Power Supply Assembly (A4): • Rectifiers for high voltage supplies • Filters for high voltage supplies • High voltage current-limit circuitry • High voltage supply-monitoring circuitry • Rectifiers for system supplies • Filters for system supplies • Regulators for system supplies • Rectifiers for fan supply • Filter for fan supply • Digital Assembly (A5) • LED front panel status annunciators • CPU, RAM, ROM, EEROM, watchdog timer, logic • Current Amplifier Assembly (A2): • Transconductance amplifier • Current shunt • Heat sink and current power devices • 5700A current routing circuits • Filters for high current supply • Rectifier bridge for high current supply • Regulators for low current supply • Current heat sink temperature monitor

Detailed Circuit Description 4 4-11 • High Voltage Power Amplifier Assembly (A3) • Power amplifier • Harness to heat sink and its high voltage power devices • Connections to the output transformers • High voltage heat sink temperature monitoring circuitry • High Voltage Sense Assembly (A6): • High voltage sense (attenuator) and calibration circuits • 5725A input and output switching relays, relay drivers • Analog monitor, an 8-bit dac, latch for mux, latch for dac • Subminiature D-type connector to the 5700A • 5700A current routing circuits • Guard crossing • AC line power selection circuitry • AC line inrush current limiting circuitry Detailed Circuit Description 4-14. Detailed circuit descriptions for each pca (printed circuit assembly) are provided next. Individual block diagrams are provided for the Current Amplifier (A2), High Voltage Amplifier (A3), High Voltage Sense (A6), and Digital (A5) assemblies. You may also find it helpful to refer to the schematic diagrams (Section 9) while reading theory for each assembly. Interconnect Assembly (A1) 4-15. The Interconnect assembly (A1) links the other five assemblies in the 5725A. The interconnect assembly contains the following parts: • Connectors and traces to interconnect the other assemblies and the fan. There are three 32-pin DIN connectors on the Interconnect pca which connect the Power Supply assembly (A4), High Voltage Amplifier assembly (A3), and Current Amplifier assembly (A2). A 64-pin DIN connector links the Interconnect assembly to the High Voltage Sense assembly (A6). A 34-pin ribbon cable connector links the Interconnect assembly to the Digital assembly (A5). Other cable assemblies attached to the Interconnect assembly go to the fan, High Voltage assembly output, and high voltage transformers. • High voltage transformer secondary-switching circuitry. Three high voltage reed relays (K013, K014, and K015) select one of three ac voltage output transformers. A fourth relay (K001) is a high voltage armature type that connects the secondaries of the low-frequency transformer in either a series or parallel fashion. The circuit board has four layers. Most connections are done on the inner two layers. One outer layer is an earth ground plane; the other outer layer is tied to the signal VCOM.

4-16. The Power Supply assembly (A4) provides regulated system supplies for all 5725A assemblies except as noted below, as well as unregulated fan supply and high voltage supplies for the High Voltage Amplifier. The assembly also includes microprocessor- controlled switching and an independent current-limit circuit. Note Other power supplies are contained on the Current Amplifier assembly (A2). The A2 assembly includes a high-current supply and a local ±20V supply. The Power Supply assembly has four sections: high voltage supply, switching, current limit, and system supply section. Each section is first briefly described, then described in detail. • High Voltage Supply Section The high voltage supply section consists of a simple unregulated power supply with the additional capability of being run at ±400V dc for normal instrument operation, or at ±50V dc for troubleshooting. • Switching Section The switching section behaves like an electronic DPST switch, which by command of the microprocessor or the current-limit section, shuts down the high voltage supplies. Microprocessor control alone can turn on the high voltage supplies in normal operation. At the board level, manual control of the switch is possible to enable stand-alone turn on of the Power Supply assembly (A4) and the High Voltage Amplifier assembly (A3). • Current-Limit Section The current-limit section shuts down the high voltage supply in a latching mode if excessive current is drawn by the High Voltage Amplifier or if the ±15V or +5V supplies fail. This section of the Power Supply assembly consists of a pair of shunts, a pair of comparators, and a system supply monitor. • System Supply Section The system supply section contains various regulated power supplies, and is comprised of five linear regulators. In addition, the system supply section contains an unregulated supply for the fan.

Detailed Circuit Description 4 4-13 High Voltage Supply Section 4-17. The high voltage supply allows normal operation from a pair of nominal 400V dc supplies, or troubleshooting operation in a reduced voltage mode with a pair of nominal 50V dc supplies. Switching between normal and reduced-voltage operation is done by removing the plug from J301 and inserting it into J303. See Section 7 for the procedure to do this. (Plug P301 is wired with both 400V and 50V transformer taps so that the 400V taps are connected in the circuit when P301 is plugged into J301, and the 50V taps are connected in the circuit when P301 is plugged into J303.) Two sets of high voltage rectifiers, CR301 through CR304 and CR310 through CR313, form bridge rectifiers for the positive and negative supplies, respectively. The output from these bridges is filtered by C301/C321 and C320/C322. The capacitor pairs are configured in series to obtain the necessary working voltage. Bleeder resistors R303, R314, R315, and R 308 discharge C301/C321 when power is removed and form a voltage divider that equalizes the voltage across halves of C301. Resistors R335, R337, R336, and R339 do the same function for C302/C322. Warning Do not rely on the power supply LEDs as an indication of the presence of high voltage. Always use a voltmeter to check for high voltage between TP307 and TP301, and between TP307 and TP304. Components CR317 and CR318 are high intensity red LEDs that provide visual indication of the presence of high voltage. These LEDs have high luminosity at low current levels. They are located in series with the bleeders for the positive and negative supplies, using about 1 mA of current for bias. Under average lighting conditions, these LEDs are visibly lit with as little as 40V on C301/C321 and C320/C322. Zeners VR306 and VR307 are normally off, as their zener voltages are greater than the forward voltage of the LEDs. However, should an LED fail, these zeners carry enough current to allow the bleeder resistors to function. Fuses F301 and F302 protect the transformer against overload in case the 400V supplies are shorted. Without these internal fuses, a short-circuit would cause excessive power dissipation in the power transformer, even though ac line current would be insufficient to blow the main fuse. Table 4-1 lists data for fuses F301 and F302, and the other internal fuses in the 5725A. Caution For safety, replace internal fuses only with fuses of the rating and type specified in Table 4-1. Surge arrestor E302 fires if the secondary voltage of the +400V supply exceeds 600V. This should only occur if the 5725A is plugged into an ac line voltage of 200V or more when it is set to 100-120V. E302 would then draw enough current to blow the main fuse, thereby protecting the 5725A. Table 4-1. Internal Fuse Data REF DES. ASSEMBLY RATING TYPE F301 Power Supply (A4) 2A, 600V Littelfuse BLS or equivalent F302 Power Supply (A4) 2A, 600V Littelfuse BLS or equivalent F201 Current Amplifier (A2) 20A, 32V Bussman AGC or equivalent F202 Current Amplifier (A2) 20A, 32V Bussman AGC or equivalent

the +400V supply. Similarly, Q312/Q319 and Q313/Q320 are series-switch elements for the -400V supply. Resistor pairs R301/R302 and R342/R343 equalize the voltage across the transistors in their "off" state. Series transistors guarantee operation within the MOSFET 500V absolute rating. The MOSFET switches are controlled by the signal at TP305. When this point is at +5V, the series connected base-emitter junctions of Q305/Q307 and Q304/Q306 are zero biased. In this condition, only leakage current flows through Q305/Q307 and Q304/Q306, which is insufficient to develop enough source-gate voltage to turn on Q301/Q317, Q302/Q318, Q312/Q319, or Q313/Q320. When TP305 is taken low, the series base-emitter junctions are now forward biased sufficiently so that the Q305/Q307 and Q304/Q306 pairs conduct with about 0.5 mA collector current. This current flows through the source-gate resistor and zener diode bias networks of Q301/Q317, Q302/Q318, Q312/Q319, and Q313/Q320. The zener diodes limit the source-gate voltage to near 15V, which is enough to turn on the MOSFETs completely without exceeding their source-gate voltage ratings. Transistors Q303/Q321, Q311/Q323, Q315/Q322, and Q316/Q324 are emitter followers that prevent Q305 and Q307 from experiencing excessive collector-emitter voltages in their "off" state. The networks of resistors, capacitors, and diodes formed by R344/C305/CR305, R327/C304/CR316 and R345/C306/CR309 are included to slow supply turn-on to prevent a transient current-limiting condition, while still allowing rapid supply turn-off. Resistors R310/R311/R306 provide a divided voltage for low-level monitoring of the +400V supply by the analog monitor on the High Voltage Sense assembly (A6). Resistors R332/R346/R347 do the same for the -400V supply. Diodes CR314, CR315, CR319, and CR320 prevent damage to the series-switches from inductive kickback during shutdown. Control over the potential at TP305 is controlled in one of the two following ways: 1. In normal operation (P301 plugged onto the E301 header where the label SYS appears, pins 1 and 2), the microprocessor strobes the control data HVSUPPLY* into U302 by pulsing HVSTROBE. This action occurs in parallel with writing HVSUPPLY* information into a latch on the High Voltage Sense assembly (A6), but there the sense of the HVSTROBE line is inverted. Transistor Q304 provides correct polarity to the clock of U302. At any time, the supply can be switched off (i.e., TP305 brought to +5V) independent of the processor by the current-limit circuitry or by SW301 pulling the "set" line of U302 high (TP306). 2. To turn on a Power Supply assembly (A4) by itself for troubleshooting, you can plug P301 onto the E302 header where the label MAN appears (pins 2 and 3). This allows momentary-contact pushbutton switch SW302 to generate a strobe signal for U302, turning the supplies on. You turn the supplies off by pressing switch SW301. You may wish to troubleshoot in the low-voltage mode by plugging the high voltage secondary plug into J303. Section 7 contains the procedures to do this.

Detailed Circuit Description 4 4-15 Current-Limit Section 4-19. Resistors R313 and R329 are current shunts for the high voltage supplies. These are connected in series with the bridge rectifiers, with the common point between the shunts being the high voltage supply common, HVCOM. The voltage developed across the +400V shunt is negative; the voltage across the -400V shunt is positive. The shunt voltages, +400V IMON and -400V IMON, in addition to being monitored by comparators in the current-limit section, are routed via the Interconnect assembly (A1) to the High Voltage Sense assembly (A6), where they are scanned by the analog monitor, and to the High Voltage Amplifier assembly (A3) to control the autobias circuitry. The negative current monitor signal is clamped by CR307 and filtered by R328 and C308 before being directly compared to 0.36V by U301B. The positive current monitor is more complicated because of its negative value. To stay within the common-mode operating range of U301A, the shunt signal is first summed with a reference voltage via the R319/R318 network, after which it is clamped by CR306 and filtered by C308. The comparator switching level is 0.18V. The summing network scales the shunt signal for equal supply trip currents. The outputs of U301A and U301B are open collector, which allows them to be wire- OR’ed with the open drain output of Q309. The output of this logic drives Q308, resetting the high voltage supply switches and signaling the processor via HVCLR. Transistor Q310 monitors the presence of the ±15V supplies. If either of these supplies fail, the high voltage supplies are switched off. System Supply Section 4-20. The digital/relay power supply tap (+5V) is routed via J350 through RT350 and bridge rectifier CR351. A positive temperature-coefficient thermistor protects the instrument from the secondary supply short circuits. This prevents them from thermally stressing the power transformer. Three-terminal regulator U350 regulates the digital/relay supply with 1% initial tolerance and about 2% accuracy over temperature. Capacitor C350 filters the input of U350; C351 filters the output. The +5V digital supply powers both logic and relays. The power for each routes away from the +5V regulator separately, via lines +5V and +5VK. This prevents relay drive currents from causing drops in the logic supply voltage. Because the ±20V supplies draw little current, they can share power transformer secondary windings with the ±15V supply with little efficiency lost. This center-tapped winding is brought to the Power Supply assembly via J350, where each half of the winding is protected from short circuits by a thermistor. Bridge rectifier CR355, as well as filter capacitors C353 and C356 again serve both supplies. The center tap of this transformer winding forms VCOM, to which PACOM and HVCOM are tied to provide a common reference for the instrument. An accurate +15V supply is obtained by using U351. Regulator U352 regulates the -15V supply. An accurate +20V supply is obtained by regulating with U353, a 5V regulator, but referencing it to the accurate +15V supply. VR351 forces U353 to be forward biased as the +15V supply comes into regulation. This avoids powering up the +20V supply through CR359 (at the improper voltage), reverse biasing U353. A discrete regulator makes the negative -20V supply accurate. U354 is an error amplifier that forces the junction of R352 and R350 to be 0V. In doing so, the -20V supply is forced to be the inverse of the +20V supply within the matching of R350 and R352. Transistor Q350 provides a pass element for the negative regulator; VR352 provides level shifting so that the drive required from U354 is within its output swing range.

4-21. The fan supply uses the same transformer secondary windings as the ±15 and ±20V supplies. Its own full-wave bridge rectifier diodes create a supply voltage of +25V. Transistor Q351 is operated near saturation, and provides the measurement point to tell the CPU whether the fan is running. The output of Q351 is sent to the analog multiplexer on line -FAN to accomplish this. Digital Assembly (A5) 4-22. From a software standpoint, digital circuitry functions as a subset of the 5700A in-guard CPU. Digital circuitry resides on three assemblies within the 5725A: the Digital assembly (A5), the High Voltage Sense assembly (A6), and the Current Amplifier assembly (A2). All the 5725A hardware, including digital, is in-guard, except for the guard crossing and the CABLEOFF detection circuit. Figure 4-2 is a block diagram of the Digital assembly. The Digital assembly contains most of the digital circuitry, including the following: • Microcomputer (Hitachi 6303Y CMOS) • External RAM (CMOS static) • External ROM • EEROM (2Kb X 8) • Break-detect circuitry • Power up and reset circuitry • Watchdog timer circuitry • Front panel LEDs • LED decoder and driver The High Voltage Sense assembly (A6) contains the optoisolator link (guard crossing) to the 5700A Main CPU and the CABLEOFF circuit. The Current Amplifier assembly (A2) contains the interface to the digital bus (two latches and three relay drivers) and a relay driver chip. Microcomputer 4-23. The 6303Y CMOS microcomputer is configured for Mode 1 operation, with external RAM and external ROM. Port 3 provides a common data bus (D00-D07), while port 1 and bits 0 through 5 of port 4 provide the address bus (A0-A13). Bits 6 and 7 of port 4 are address lines A14 and A15. External RAM 4-24. External RAM is enabled whenever A15 is high, A14 is low (hex 8000-BFFF), and either RD* or WR* is true. Reading and writing is controlled by bit 2 of port 7. External ROM 4-25. The external ROM (U515) is enabled via ROMSEL* whenever A15 and A14 are high (hex C000-FFFF). Bit 0 of Port 7 (RD*) is OUTPUT ENABLE*.

Detailed Circuit Description 4 4-17 aq19f.eps Figure 4-2. Digital Assembly Block Diagram

temperature of calibration. If the rear panel CALIBRATION switch is in the NORMAL position, the EEROM is software write disabled. The 6303Y reads the CALIBRATION switch via bit 1 of port 5 and enables the EEROM when the switch is in the ENABLE position. The EEROM is selected when A15 and A14 are low, A13 is high (2000 through 3FFF), and either RD* or WR* is TRUE. Writing is controlled by bit 2 of port 7 and the RESET* line. The 5725A does not automatically format its own EEROM. The 5725A informs the 5700A Calibrator if a problem has been encountered at power-up. The 5700A assumes responsibility for formatting the 5725A EEROM. Data Latch 4-27. The Data Latch (U510) is enabled via LATCHSEL when three conditions are met: address bit A15 is 0, A14 is 1 (hex 4000-7FFF), and WR* is 0 (true). Data Latch U510 (a 74HCT373) latches information on the external data bus (D0-D7) and sends this information to the LED latch (U501), Current Amplifier assembly (A2), and the High Voltage Sense assembly (A6). Strobe Lines 4-28. The Current Amplifier (A2) and High Voltage Sense (A6) assemblies tie to the Data Latch external data bus output with latching relay drivers and/or latches. Information is strobed into the respective relay drivers/latches by the state of any of the seven strobe lines. The seven strobe lines (STROBE 1-5,21,22) and a clear line (CLR), all asserted high, are buffered (U503) outputs on port 6. An additional strobe line called HVSTROBE, for use by the High Voltage Sense and Power Supply assemblies, is created from STROBE 2 combined with STROBE 2 ENABLE* and HVSUPPLY*. Line HVSUPPLY* is generated on the High Voltage Sense assembly. The strobe rate varies from 50 ms for STROBE 2 to over 100 ms for the other strobe lines. The CLR line opens all relays except K202. Led Driver 4-29. Front panel LEDs are driven by U501, a 74HCT373 latch, which is capable of sinking 35 mA of LED operating current. An output LOW turns an LED on. The LED driver is selected by bit 7 of port 5, LEDSEL. Optoisolator Link 4-30. An optoisolator circuit links the two-channel guard crossing. This guard crossing circuit and the related 5725A/5700A interconnection reside on the High Voltage Sense assembly (A6). Serial communication to and from this guard crossing uses the RECEIVE and TRANSMIT lines, respectively. When the 5725A is not being used, all cable inputs into the 5700A are tied to the 5700A guard to shunt noise currents away.

Detailed Circuit Description 4 4-19 Break-Detect Circuitry 4-31. The 6303Y divides the 4.9152-MHz crystal frequency by four to create the 1.2288-MHz ECLK. This signal serves as the clock for the 74HC4020 counter (U506), which is configured as a divide-by-16384. The RECEIVE line is usually high, except for the brief interval when characters are being transmitted. As long as the low state is less than 13.34 ms, RECEIVE holds the CLR of the 74HC4020 TRUE. However, if communication between the 5725A Amplifier and the 5700A Calibrator fails, the 5700A attempts to reset the 5725A by sending a break (holding RECEIVE low for greater than 26.7 ms). This action causes the 74HC4020 counter output (BREAK) to go high. Signal BREAK is NOR’ed with CABLEOFF from the High Voltage Sense assembly (A6); either signal causes a NON-MASKABLE INTERRUPT to the 6303Y. The 5700A also uses BREAK to reset the 5725A. Power Up and Reset Circuitry 4-32. Reset and glitch-detection circuitry primarily consists of U508, a TL7705A. This chip detects if the power supply falls below 4.5V, if a reset input from a momentary contact switch occurs, or if there is an output from the watchdog timer. Any combination of these conditions resets the board via RESET* for 130 ms. Watchdog Timer 4-33. Watchdog circuitry contains a 4538 Dual Monostable Multivibrator. The first multivibrator (U509A) is configured as a 300 ms retriggerable one-shot that can fire a second 3 ms one-shot (U509B). Control line STROBE 2 of the 6303 (bit 1, port 6) retriggers the first one-shot every 50 ms and refreshes the high voltage relay driver. If STROBE 2 is stuck high or low during operation, the first one-shot is no longer retriggered, and its output transitions low. The second one-shot, configured to trigger on a falling edge, now sends a pulse via RESIN* to the TL7705A reset IC U508. This action forces the reset circuit to pull a hard reset on the 6303Y for 130 ms. The first trigger to the 4538 occurs when the 7705A RESET* line makes a transition from low to high. During normal operation, STROBE 2 prevents another reset by retriggering the first one-shot well before the 300 ms timeout. The watchdog fires only if the CPU is executing erroneous code which does not activate STROBE 2. Current Amplifier Assembly (A2) 4-34. The Current Amplifier assembly enables the 5725A to extend the current output range of the 5700A Calibrator to ±11A dc or 11A ac. The 5700A drives the Current Amplifier assembly input through the 5725A interface cable. There are no user input terminals. Output current is available at binding posts on the 5725A front or rear panel. Selection of front or rear 5725A binding posts is done by unplugging one cable and plugging in another cable on the Current Amplifier assembly inside the 5725A chassis. Additionally, relays on the Current Amplifier assembly can route the 5700A current source to the 5725A output terminals, if so selected at the 5700A front panel (or by remote command). The Current Amplifier assembly has five distinct sections: the error amplifier, output, control, monitor, and power supply. Each section is first briefly described, then described in detail in the following paragraphs. Refer to Figure 4-3, a block diagram of the Current Amplifier assembly, to see the interrelationship of the following function blocks.

Detailed Circuit Description 4 4-21 • Error Amplifier Section The error amplifier section contains three differential amplifiers and a precision high-current shunt resistor. Two differential amplifiers set the gain and uncorrected frequency response of the current amplifier. The remaining differential amplifier is used during the internal portion of 5700A/5725A calibration and during ac current operation. • Output Section The output section contains several power transistors, a heat sink, two operational amplifiers, a current buffer amplifier, two current sensing resistors and related components. The output stage is driven by the error amplifier section, converting a ±3V signal into a ±15A signal. The output section is powered by floating supplies that are referenced to the ICOM current common. The output stage is designed to drive inductive loads. • Monitor Section The monitor section contains several op amps and comparators, and a thermistor. A temperature monitor circuit observes the temperature of the voltage output transistors. Excessive output compliance voltage is detected by the drive monitor circuit. Both monitor circuits send scaled voltages to a multiplexed comparator on the High Voltage Sense assembly (A6), where abnormal operating conditions are detected. • Control Section The control section contains nine relays, a latched relay driver, several transistors, and a quad comparator. The relays and transistors switch the Current Amplifier into ac current and dc current operating states, a standby state, and several self calibration and diagnostics states during which 5725A operation is monitored and characterized by measurement circuitry and software residing in the 5700A. • Power Supply Section The power supply section contains two bipolar power supplies. Regulated ±20V supplies and unregulated ±12V supplies are referenced to ICOM and power only the output section. The error amplifier section and control section are powered from the ±15V and +5V 5725A system supplies. Error Amplifier Section 4-35. Refer to page 1 of the Current Amplifier schematic. Components U201, Z201, R235, C230, and Q211 make up the "outer loop error amplifier," a differential amplifier with high common-mode rejection ratio. The outer loop error amplifier controls a first-order feedback loop that determines the dc accuracy and uncorrected ac frequency response of the current amplifier. Q211 shuts off the outer loop error amplifier during standby and, through modulation of its channel resistance by R255 and C210, yields a soft-start transition into the operate modes. Components U202, R232, R241, R251, R252, R234, C213, and Q213 comprise the inner loop error amplifier. The inner loop error amplifier works with the outer loop amplifier in a second-order feedback loop that significantly diminishes the effects of output stage non-linearities. Q213 reduces the inner loop gain during standby. Refer to page 2 of the Current Amplifier schematic. Resistor R272 is a specially constructed 0.02Ω shunt resistor that senses the Current Amplifier output. U208 and Z203 comprise a gain of ten differential amplifier called the calibration amplifier (Cal Amp). The calibration amplifier scales the voltage dropped across R272, creating a signal

The calibration amplifier output is measured by circuitry within the 5700A during calibration of the 5725A current amplifier. The calibration amplifier output is fed back to the 5700A Oscillator during ac current operation. The feedback signal from the precision shunt is applied to both the inner and outer loop error amplifiers (ISENSE HI, ISENSE LO , pages 1 and 2). The error amplifier section drives the output stage (TP204) so that the voltage across R272 is one-tenth of the Current Amplifier input voltage (VINI). Thus, the Current Amplifier is a transconductance amplifier: output current is proportional to input voltage. This transconductance is -5A/V. Output Stage Section 4-36. Refer to page 1 of the Current Amplifier schematic. Components U203, R203, R204, and R209 convert the bipolar ground-referenced output signal from the error amplifier section into two unipolar supply-referenced waveforms at the inputs to U204A and U204B. IC U203 also isolates the output stage, which is referenced to a floating common (ICOM), from the rest of the circuitry, which is referenced to circuit common (VCOM). The operation of the positive and negative output halves are similar. Only the positive output section is described below. In response to a positive polarity error amplifier output (TP204), the current through R209 increases. This same current flows into pin 2 of U203, causing the voltage drop across R203 to increase. The voltage across R203 is applied to the positive input of U204A. U204A drives Q203, Q205, and Q207 until the voltage at the emitter of Q207 is identical to the voltage at the non-inverting input of U204A. Test point TP204 is a test input for the output stage when in standby mode. The resulting output stage current can be monitored at TP208 with a scaling of 200 mV/A. The quiescent operating point of the output devices is fixed by the bias current of U203 and current source CR205 at about 1A. There is no output stage bias adjustment. Capacitor C235 and resistors R256 through R260 provide a tertiary feedback path that guarantees stability when the 5725A is driving the specified inductive loads. Monitor Section 4-37. Refer to page 1 of the Current Amplifier schematic. Components U211C and D, U210C, RT203, CR207, and associated resistors and capacitors make up the temperature- monitoring circuit. Heat sink temperatures above approximately 85°C signal the ITEMPM fault condition. Components U207, R280 through 284, and C234 generate a negative voltage at TP207 (DRIVE MONITOR) that remains less than 3.1V in magnitude when the output compliance voltage is within the linear operating range of the output stage. The output compliance voltage is not measured by the drive monitor circuit; an overcompliance condition is inferred from excessive error amplifier output.

Detailed Circuit Description 4 4-23 Control and Switching Section 4-38. Refer to page 2 of the Current Amplifier schematic. Relays K201 through 209, Q214 through 216, and U209 through 210 configure the Current Amplifier circuitry for the following six modes: • Current Standby Current Amplifier input is active through K201. Current Amplifier output is disconnected from instrument output terminals but is routed through the sense path through K202. • Operate1 Input is connected to BOOST IN and MCOM. Output is connected to front or rear output terminals. FET switches Q211 and Q213 are off, enabling the error amplifier circuitry. Operate1 is the active mode for delivering up to 11A (ac or dc) to a UUT. • Operate2 The Current Amplifier is configured as in standby mode, except K201 is off. 5700A current source is routed to the 5725A current output terminals through K205. Operate2 is the active mode for delivering 2.2A or less to the 5725A terminals unless the 5725A 11A current range has been explicitly enabled from the 5700A front panel or by remote command. • Calibrate1 (Shunt Calibration) Input is shorted. Error amplifiers are disabled with Q211 and Q213. Output is routed directly to current return path through K207, bypassing sense circuits. 5700A current source is routed through K206 to the 5725A current sense path. Procedures performed during Calibrate1 determine the value of R272. This is one of the factors in the dc gain and the only factor in the ac gain of the Current Amplifier. • Calibrate2 (Offset Calibration) The amplifier is configured as in Calibrate1, except with its output routed by K208 to the 5700A. Procedures performed during Calibrate2 determine the dc offset of the Current Amplifier. • Calibrate3 (Gain Calibration) Input is connected to BOOST IN, B-FEEDBACK, and MCOM as in Operate1, but Output is routed through the current sense path through K202. Output is not connected to output terminals. Procedures performed during Calibrate3 determine the gain of the error amplifier, the other factor in the dc gain of the Current Amplifier. Power Supply Section 4-39. Refer to page 3 of the Current Amplifier schematic. The unregulated, high-current supply is made from K208 through 209, F201 through 202, CR206, and C218 through C221. The regulated ±20V supplies are composed of RT201 through 202, U205, U206, CR212 through 215, C222, C223, and associated components. Thermistors RT201 and RT202 are PTC thermistors for current limiting and transformer protection.

4-40. The High Voltage Amplifier assembly, operating with the step-up signal transformers, constitutes an amplifier with an inverting gain of 100. It amplifies 2.2V to 11V signals from the 5700A Oscillator and returns 220V to 1100V to the 5700A where they go to the 5700A OUTPUT HI/OUTPUT LO binding posts. The signals to and from the 5700A come through the High Voltage Sense assembly (A6) where they are switched. The High Voltage Amplifier assembly consists of an input amplifier, integrator, window comparator, input clamp, transconductance and cascode stage, midstage, midstage -400V filter, high voltage heat sink assemblies, autobias current source, autobias sense circuit, high voltage amplifier feedback, and temperature monitoring circuits. The High Voltage Amplifier drives the primary winding of the appropriate signal transformer depending on the frequency of operation. Signal transformers are interfaced to the High Voltage Amplifier via connector J604. Relays that select signal transformers are mentioned under the heading "Signal Transformers" further on. The High Voltage Amplifier assembly uses the ±400V supplies from the Power Supply assembly. Lethal voltage appears on the heat sink assemblies. Do not open the 5725A cover without referring to the access procedures and warnings in Section 6. Figure 4-4 is a block diagram of the High Voltage Amplifier assembly. Refer to the block diagram or the schematic to better understand theory of operation. Input Amplifier 4-41. The input amplifier, U602, is an op amp whose input comes from HV IN on J653 through R623 and R621. HV IN is the 2.2V to 11V ac signal generated by the 5700A and routed through the High Voltage Sense assembly. The input amplifier has a high- frequency gain of 5.5, but because feedback resistor R622 is ac-coupled through C615, the gain is much higher at low frequencies. The inverting input of U602 is buffered with Q601. The nominal output of the input amplifier, LVAMP TP602, is about 6V dc.

Detailed Circuit Description 4 4-25 aq22f.eps Figure 4-4. High Voltage Amplifier Assembly Block Diagram

amplifier circuit. This integrator senses the output voltage of the amplifier (MVOUT) through R604 and R605 and forces it to be zero with respect to HVCOMM. Window Comparator 4-43. Comparators U604A and U604B form a window comparator that monitors the output of the input amplifier, U602. The window is set to about +2.2V to +9V by R626, VR602, and R636. If the output of U602 exceeds the window limits, the appropriate comparator turns on the clamp, Q604, shorting the input to ground. The comparator also pulls control line CLAMPS high via U604D, where the comparator routes to the Digital Assembly (A5) through the Interconnect assembly (A1). Comparator U604D is a level shifter to translate the window comparator output to a TTL level. Exceeding the limits of the window comparator is an indication that the loop is in an abnormal condition when the instrument is in the ac voltage standby or ac voltage operate states. In current standby or current operate states, the comparator causes CLAMPS to be asserted, which turns off the +400V and -400V supplies. Input Clamp 4-44. A FET clamp, Q604, is turned on until the output of U602 returns to the region within the window. When this occurs, the comparator turns off Q603. To avoid a large transient at the output of the High Voltage Amplifier assembly (A6), the clamp must be turned off slowly. Resistor R637 and C618 slow the clamp drive signal to accomplish this. Though Q604 can be turned off slowly by removing its gate drive slowly, it clamps asymmetrically in the transition region. The body of the FET is held at -7.5V. This keeps the FET from turning on at the negative peaks of the input waveform. The asymmetrical clamping appears as a dc shift in the waveform, which can cause the transformer to saturate. To alleviate this problem, a second clamp is placed in parallel with Q604. This second clamp is the photoresistor portion of the optical isolator, U605. It has a considerably higher on resistance than Q604, so the two are used together. When the clamp is to be turned off, Q603 is turned off and the voltage on C618 begins its transition from nearly +15V to -15V. At +15V, Q604 is turned on but because Q605 is also on, shunting current from the input of U605, the photoresistor is in the high impedance state. When the voltage on C618 reaches about +9V, Q605 turns off and the optoisolator is turned on, putting the photoresistor into its low resistance state. This has little effect on the input signal because the photoresistor is a higher impedance than the FET. As the control voltage approaches zero, Q604 turns off and the input is clamped only by the photoresistor. As the control voltage continues toward -15V, the photoresistor makes the transition to its off, or high impedance state. The photoresistor clamps symmetrically, eliminating the dc transient on the input. A similar transition takes place when light turns on the clamp but it happens much faster, as the turn-on transition is controlled by the time constant R631*C618 which is about an order of magnitude faster than the R637*C618 turn-off time constant. The microprocessor on the Digital assembly can also pull the clamp via control line CLAMPD, which is latched into a driver on the High Voltage Sense assembly (A6). Line CLAMPD is asserted during a sequenced turn on, power down of the High Voltage Amplifier assembly (A3), or during a transition to another frequency range. Comparator U604C level shifts CLAMPD and provides an OR function with the window comparator output.

Detailed Circuit Description 4 4-27 Transconductance and Cascode Stage 4-45. The output voltage of the input amplifier U602, LVAMP, is transformed into a current by Q602. The nominal current is about 8.5 mA. This implies that the nominal output voltage of the input amplifier is about 6V; 15V - (.0085 * 1000) - .6 = 5.9V. The current is passed through a cascode FET Q661, which can stand off the voltage required, about 400V. A zener diode similar to VR656 protects most of the power MOSFETs from damage to their gate oxide layer by excessive gate voltage (approximately ±20V). A gate resistor similar to R675 suppresses high frequency oscillations. Midstage 4-46. The current from Q661 generates a voltage of about 8.5V across R698. The ac voltage gain from TP602, the LVAMP output, to R698 is unity. Transistor Q666 mirrors the current into the midstage with an ac gain of 5. The dc midstage current is about 28 mA. The midstage current passes through two cascode FETs, Q662 and Q665, to bias resistor R674. Transistor Q660, VR658, and R678 form a 21 mA current source that, along with R674 establishes the midstage bias current at about 28 mA. FET Q653 is a current source from the +400V supply controlled by the auto-bias circuitry. The bias for Q654 and Q662 comes from the high voltage heat sink assemblies and is maintained about halfway between the output voltage and the +400V supply or -400V supply, respectively. The bias for Q665 comes from zener VR665, FET Q667, and its associated parts, which form a 3 mA current source to bias the zener. Zener VR661 provides some additional protection for Q665 and Q666. Capacitor C660 and R612 provide the dominant pole to stabilize the midstage amplifier. Gain-bandwidth is set to about 7 MHz. Midstage -400V Filter 4-47. FET Q670 is a filter to reduce the 120 Hz and output signal ripple on the -400V supply. Zener VR663, acting as a normal diode, clamps the gate of Q670 at the positive peak of the ripple on the -400V supply. As soon as the -400V supply moves away from the positive peak, the gate voltage is heavily filtered by R695 and C663. The zener action of VR663 and VR664 prevents Q670 from being damaged by excessive gate voltage as the -400V supply is turned on. High Voltage Heat Sink Assemblies 4-48. The output power MOSFET devices are mounted in pairs on the four high voltage heat sink assemblies. Each pair is driven with the same gate voltage. To ensure they equally divide the current, the MOSFETS are matched for gate-source voltage at 0.5A and have 3.9Ω source resistors. The push-pull output stage consists of Q655 and Q656 on the N- channel heat sink assembly #2 and Q663 and Q664 on the P-channel heat sink assembly #2. Their gates are driven with the voltage on R674. Resistors R670 through R673 sense the output current, while Q658 and Q659 limit the current to about 2.4A. Diodes CR652 and CR654 help to reduce the amount of stored charge in the power MOSFETs that must be driven when they are turned on and off. The power MOSFETs on the #1 heat sink assemblies are driven cascode to share the voltage drop between the output (MVOUT) and their respective 400V supply. This also balances their power dissipation with the #2 heat sink assemblies. Their gates are driven from the voltage divider R654 and R661 or R684 and R692. Capacitors C654 and C661

sink assemblies. Their sources establish the voltage on the gates of the cascode FETs in the midstage, Q654 and Q662. The power MOSFETs are in the TO3 package and are mounted to the heat sinks using a heat conductive pad (electrically conductive as well) to minimize thermal resistance to the heat sink. This means that the heat sinks can have ±400V on them during normal operation. Do not open the 5725A cover without referring to the access procedures and warnings in Section 6. Lower voltage supplies of about ±50V are available on the board to replace the ±400V supplies during test and troubleshooting. How to power up in the reduced-voltage troubleshooting mode is described in Section 7. The four heat sink assemblies are attached to the High Voltage Amplifier assembly (A3) via connectors P661-664. A thermistor is stud mounted to the P-channel heat sink assembly #2 and attaches to the High Voltage Amplifier Assembly through J603. The temperature monitoring circuit, described further on, uses this thermistor. Autobias Current Source 4-49. FET Q653 is a current mirror that provides a dc current to bias the midstage. FET Q654 is a cascode stage to share the voltage and power. Since the loop forces the dc output of the amplifier back to zero if the midstage current is increased, the effect of increasing the midstage current is to increase the voltage drop across R674. Midstage current is increased until the gates of the output devices (connected to either end of R674) are driven just hard enough to establish the desired idle current in the output stage. The current that Q653 mirrors comes from Q657, which is driven by BIAS from the Autobias Sense Circuit. FET Q657 stands off the high voltage to the +400V supply and makes the autobias circuit less sensitive to its ripple. Autobias Sense Circuit 4-50. The autobias sense circuit senses the +400V IM from the Power Supply assembly (A4). Signal +400V IM is a voltage developed across a R313 in the low side of the +400V supply, which provides a voltage proportional to the current in the 400V supply. If the High Voltage Amplifier were operating Class B, the +400V IM waveform would be half sines for a sinusoidal output current waveform. The autobias sense circuit forces the average current in the +400V supply to be greater than the average of a half sine to produce Class A-B operation. This results in Class A operation for small output currents and for high output currents, a +400V IM waveform that looks like a half sine at the peak but is more rounded at the base. The autobias sense circuit does this by measuring the average of +400V IM and comparing it to the peak of +400V IM / pi (the average that would have been obtained for Class B operation), plus an offset. Op amp U606A and C621 are configured as a peak detector. Resistors R647 and R648 divide the peak by pi. Resistor R643 and the 15V supply provide the offset: (15V * 10K) / (4.3M * 0.39) = 90 mA. These signals are summed into integrator U601B. The integrator is an error amplifier that drives the autobias current source circuitry, via BIAS, to achieve the desired relationship between the peak and average values of the current delivered by the +400V supply.

Detailed Circuit Description 4 4-29 Op amp U606B senses the -400V supply and forces the autobias to the minimum bias condition when the ±400V supplies are turned off. Transistor Q606 forces the minimum bias condition when the window comparator is activated. High Voltage Amplifier Feedback 4-51. Feedback for the High Voltage Amplifier is provided by R606, R607, and R608 from the output signal MVOUT. This means that the high voltage signal transformers are driven open loop by the High Voltage Amplifier. Feedback for amplitude leveling is provided on the High Voltage Sense Assembly (A6). The turns ratio of the hf transformer is less than the other transformers. Resistor R608 compensates for the difference in turns ratio so the overall gain of the High Voltage Amplifier, plus the signal transformers, is -100 independent of frequency range. Resistor R608 is switched in by K601 only in standby mode and in hf operation. Signal Transformers 4-52. Three transformers cover the four frequency ranges as shown in Table 4-2. The lf transformer is a C-core. The mf and hf transformers are toroids. All three signal transformers are located in the transformer box on the left side of the instrument when viewed from the front. Table 4-2. Signal Transformer Usage FREQUENCY RANGE TRANSFORMER TURNS RATIO HIGH VOLTAGE AMPLIFIER OUTPUT(MVOUT) HIGH VOLTAGE TRANSFORMER OUTPUT 40 Hz to 120 Hz LF (Series) 1:5.5 40 to 200V 220 to 1100V 120 Hz to 3.4 kHz LF (Parallel) 1:5.5 40 to 200V 220 to 1100V 3.4 kHz to 30 kHz MF 1:5.5 40 to 200V 220 to 1100V 30 kHz to 100 kHz H F 1:4.5 49 to 167V 220 to 750V Four control lines: HFPD, MFPD, LFPD, and VLFPD, control the frequency ranges. The control lines are generated on the High Voltage Sense assembly. These lines control relays K601 to K604, which direct the High Voltage Amplifier output to the primary of the appropriate transformer and switch in feedback resistor R608 to compensate for the hf transformer turns ratio. Relay K604 switches the primary windings of the lf transformer into a series connected configuration for 40 to 120 Hz operation, and into a parallel connected configuration for 120 Hz to 3.5 kHz operation. Relays on the Interconnect assembly (A1) switch the secondary transformer windings. These Interconnect relays are driven by the same control lines as the High Voltage Amplifier assembly. These lines originate from latch/driver U157 on the High Voltage Sense assembly (A6). Temperature Monitoring 4-53. The temperature monitoring circuit estimates the junction temperature of the power MOSFETs by measuring the temperature of one of the high voltage heat sinks and adding a calculated temperature rise from heat sink to junction, based on the current in the +400V supply. The heat sink temperature is sensed with a stud-mounted thermistor mounted into the P- channel heat sink #2 via connector J603. Its negative temperature coefficient is linearized

about -0.77V. This reference voltage is applied to the circuit containing summing amplifier U603B, R611, and the linearized thermistor. The output of U603B is signal HV TEMP M, equal to 10 mV/°C. A voltage proportional to the temperature rise from the heat sink to the junction of the transistor is added to HV TEMP M through R610. This is done via +400V IM from the Power Supply assembly. Resistor R610 is selected to properly scale this contribution to the 10 mV/°C output of U603B. Capacitor C610 provides averaging for the ripple on the current-sensing resistor, and CR604 prevents C610, an electrolytic capacitor from being reverse charged. High Voltage Sense Assembly (A6) 4-54. In addition to ac voltage sensing for which it is named, the High Voltage Sense assembly provides four major functions for the 5725A. These additional functions are the following: • Analog monitoring of the 5725A status • Interface with the 5700A controller • Switching input signals from the 5700A • AC Line Power switching Because it performs all the above functions, the High Voltage Sense assembly plays a primary role in controlling the instrument, attaining ac voltage specifications, performing 5725A calibration, and maintaining instrument safety. The High Voltage Sense assembly has the following six sections: sense amplifier, analog monitor, serial interface/guard crossing, analog input switching, control, and mains switching. Each section is first briefly described, then described in detail. For reference, see Figure 4-5, the block diagram for the High Voltage Sense assembly. • Sense Amplifier Section The sense amplifier section consists of a precision ac amplifier configured as an active attenuator, a buffer amplifier that isolates the 5725A high quality ground from the 5700A ground reference, and a precision true rms converter circuit for 5725A calibration. Together, these circuits accurately attenuate the output of the 5725A in ac voltage function to drive the 5700A Oscillator control circuitry. The sense amplifier section is essentially a gain-determining feedback element of a loop whose forward path consists of the 5700A Oscillator and the High Voltage Amplifier assembly (A3). • Analog Monitor Section The analog monitor section is comprised of a bipolar output dac, a comparator, and a 16-channel multiplexer. The inputs to the multiplexer are scaled voltages representing critical parameters in the other 5725A assemblies, particularly those involving high voltage and/or current. Each input can be compared to programmed limits set by the dac under microprocessor control. The comparator gives simple go/no go decisions, which are then acted on in a more sophisticated way by the software. An additional function of the analog monitor section is to provide access to the B-RCL line used by the 5700A during 5725A calibration.

Detailed Circuit Description 4 4-31 aq21f.eps Figure 4-5. High Voltage Sense Assembly Block Diagram

The serial interface/guard crossing section consists of an RS-232 interface integrated circuit that provides the hardware for 5700A/5725A communication within the 5725A. Two optoisolators provide the serial guard crossing to the Digital assembly (A5), and two more provide integrity checks for the interface. A relay remotely powered by the 5700A provides a software independent path to guarantee 5725A shutdown if the 5700A/5725A cable is disconnected. • Analog Input Switching Section The analog input switching section consists of a bank of relays that route ac and dc voltages and dc currents from the 5700A to various functional blocks inside the 5725A. Assemblies that receive inputs from the Analog Input Switching Section are the High Voltage Amplifier assembly (A3); the Current Amplifier assembly (A2); and the sense amplifier section of the High Voltage Sense assembly. • Control Section The control section is implemented with a bank of four latches connected to the microprocessor data bus. A pair of latches with their integral drivers control relays, a pair of latches control the 16-channel multiplexer and the bipolar output dac in the analog monitor section. • AC Line Voltage Switching Section The ac line voltage switching section is independent of the other five sections of the High Voltage Sense assembly. The ac line voltage section contains three switches (labeled S2, S3, and S4 on the rear panel) that configure the input to the transformer to accept one of eight nominal line voltage levels. Also included in this section are a simple unregulated power supply and a time delayed relay driver circuit. These circuits control a shunt switch around a pair of surge current-limiting NTC thermistors. Caution To avoid meter damage, do not measure the ac line voltage section unregulated supply with a meter tied to earth ground. Sense Amplifier Section 4-55. Op amp U102, transistors Q100 through Q103, and their associated parts comprise the forward gain elements of a precision ac amplifier. Since this monolithic device does not accept supply voltages large enough to accommodate output swings of ±15.6V, a quartet of discrete transistors is configured as an output stage with voltage gain. This provides the necessary output swing of 11V rms as well as limits the additional forward gain of the overall amplifier to simplify frequency compensation. Inputs to the output voltage stage are derived from deviations of the supply current of U102 from its quiescent value. This topology depends on the increase in current from a particular power supply as the output of the monolithic op amp moves toward the value of that power supply. This increasing current develops a drop across R108 for positive output voltages or a drop across R116 for negative output voltages. These drops are amplified by Q100 and Q103. Transistors Q101 and Q102 buffer the output signal to present a low source impedance to the load. Overall gain at low frequencies is controlled by Z100, a resistor network designed for good ac frequency response, low power coefficient, and low thermal settling time. This network provides a feedback ratio of 0.99, or a closed-loop gain of 0.01. As a result, the entire sense amplifier is running in a virtual unity gain configuration. Zeners VR103 and

Detailed Circuit Description 4 4-33 VR105 reduce apparent supply voltage seen by U102. Transistors Q105 and Q106 along with R131/C117 and R132/C118 filter the supply to reduce common mode errors at high frequency. Capacitor C108 provides ac tuning for the sense amplifier. This capacitor balances most of the parasitic capacitance picked up across the input resistor portion of Z100. Capacitor C109, in parallel, provides fine adjustment of response if needed. Components L105 and R130 isolate capacitive loads from the output of the sense amplifier to aid in achieving stability. Transistor Q104 is necessary to route the output of the sense amplifier to the 5700A during calibration. The signal routes to the B-RCL line (the high-quality dc line to the 5700A calibration circuitry) through the analog monitor section’s 16-channel multiplexer. This device cannot handle the output swing of the sense amplifier (±15.6V) without risking inadvertent functional failure because of its ±15V supply limits. The result is to isolate the multiplexer from the sense amplifier output during normal operation with the JFET switch Q104, which is then also turned on during calibration. This is possible because the output of the sense amplifier is nominally ±3.2V during calibration. During ac voltage operation, the input of the sense amplifier is either locally driven via K104, or remotely driven via K105 and K109, by the High Voltage Amplifier assembly (A3). Op amp U103 forms a simple low offset voltage, low input current buffer to isolate the B-SENSE LO line from the rest of the 5725A circuitry. B-SENSE LO is the reference sense signal from the load provided through the 5700A and 5700A/5725A cable. Buffering B-SENSE LO ensures that the current flowing between the load and the 5700A Switch Matrix assembly along this reference sense line is minimized, and as a result, the series voltage drop is minimized. The buffered B-SENSE LO line is distributed throughout the 5725A as MCOM, MCOMI, MCOMV, and MCOMC. These lines are all at the same potential, but they have different names corresponding to different paths taken to control the flow of ground currents. These names correspond to destinations as shown in Table 4-3. Table 4-3. High-Quality Reference Name Destination REFERENCE NAME DESTINATION (ASSEMBLY) MCOM High Voltage Sense (A6) MCOMI Current (A2) MCOMV Reference for high voltage input to calibration circuit, High Voltage Sense (A6) MCOMC Calibration circuit section of the High Voltage Sense (A6) The ac calibration circuit is also in the sense amplifier section. This circuit provides an extremely flat ac response for 5725A calibration of the sense amplifier. This flat ac response is made possible by the use of U101, the Fluke rms sensor, and a low- impedance ranging resistor, R103. The value of this resistor is 50 times less than the input resistor within Z100; as a result, the effect of parasitic capacitances is reduced by 2500. A protection circuit made up of CR101, CR102, VR101, and VR102 clamp input voltages. Op amp U100 is a forward gain block, configured as an integrator with U101. A feedback circuit results, whose output at TP106 is a dc voltage proportional to the rms value of the signal applied to R103 and the input sensing resistor of U101. Resistor R112 provides a simple means of protecting the output half of U101, while CR100 prevents

U100. Op amp U105 is simply a low-noise inverting amplifier that scales the sensor output to 10 dB below the 5700A Oscillator output level. The output of the calibration circuit, AC/AC, goes to the 5700A during calibration through the analog monitor section. Analog Monitor Section 4-56. The 16-channel multiplexer, U151, takes a variety of inputs from all analog assemblies and provides a means of switching them to either a comparator, U154A, or to the B-RCL line via K152. During normal operation, the multiplexer output is routed exclusively to the comparator. Calibration requires routing the multiplexer output to the B-RCL line, which is routed back to the 5700A. The B-RCL line is measured by the precision adc circuit on the 5700A DAC assembly. All inputs to the multiplexer are scaled so that inputs are within its ±15V power supply range. Table 4-4 shows the signal name of the multiplexer input, its description, origin, and purpose. The state of the multiplexer is controlled by the microprocessor via data latched into U152. Table 4-4. Signals Monitored by the Analog Monitor Section STANDBY VOLTAGE LIMITS(1) SIGNAL NAME PHYSICAL PARAMETER SOURCE PURPOSE -0.125V +400V IM Supply Current Power Supply Monitoring +0.125V -400V IM Supply Current Power Supply Monitoring 0.26V +400V M Supply Voltage Power Supply Monitoring -0.26V -400V M Supply Voltage Power Supply Monitoring  VCOM System Supply Common Power Supply Monitoring  HVCOM M High Voltage Supply Common Power Supply Monitoring 1.7V HVTEMP M Voltage Amp Heat Sink Temp. High Voltage Amplifier Monitoring 2.0V ITEMP M Current Amp Heat Sink Temp. Current Amplifier Monitoring -2.2V ICOMPL M Current Output Stage Drive Level Current Amplifier Monitoring  I CAL/I FB Shunt Voltage Current Amplifier Calibration, AC I Operation  AC/AC Calibrator Output High Voltage Sense Calibration  HVSENSE Sense Amp Output High Voltage Sense Calibration  DAC OUT DAC Output High Voltage Sense Monitoring 0.08, 2.0V FAN M Fan is On or Off Power Supply Monitoring Note 1: For single limit values, the limit is equal to, or smaller in magnitude to, the value shown.

Detailed Circuit Description 4 4-35 IC U156 is a dac whose digital input is under microprocessor control via data latch U155. The +15V supply is the dac’s reference voltage. Op amp U153A acts as a current- to-voltage converter, providing outputs between 0V and -6.375V. The desired output for the analog monitor function ranges from -2.56V to +2.56V. Level shifting and scaling is accomplished by U153B, by summing the output of U153A and the reference voltage for U156. Op amp U153B also forms an active two-pole filter to reduce wideband noise. The output of the dac is routed to both the multiplexer, U151, and the analog monitor comparator, U154A. Resistors R171 and R170 provide a small amount of positive feedback around U154A to ensure noise-free operation for small input voltages. Q150 forms a simple inverter that converts the comparator output to 5V logic levels. This output, MONCOMP, is routed back to the 5725A Digital assembly (A5), where it is acted on by the microprocessor. Serial Interface/Guard Crossing Section 4-57. The control link between the 5700A and the 5725A consists of a serial interface at the hardware level. Serial data signals arrive via B-RCV and leave via B-XMIT. These are translated to and from standard 5V logic levels by U160, an RS-232 interface chip that runs from a single 5V supply. Internal charge pumps use C158 through C161 to generate RS-232 compatible supply levels of ±10V. A pair of dual optoisolators, U159 and U161, isolate the serial interface signals from the remainder of the 5725A circuitry. The serial interface uses half of each pair. The other half of U161 signals the status of the 5700A/5725A interface cable to the microprocessor. A 5V supply is available from the 5700A via pins 19 and 20 of J101. This supply drives the optoisolator LED when the cable connections are intact. The 5V supply also provides coil drive for K153. This relay’s contacts are in series with the coils of the other relays on the High Voltage Sense assembly. Thus, if the cable becomes disconnected, all relays on the High Voltage Sense assembly automatically open. The relays are configured so that safety is maximized when they are open. The remaining half of U159 signals to the 5700A when the 5725A is powered up. The 5725A +5V supply powers the LED of the optoisolator, whose output pulls B-CINT* (pin 21 of J101) toward the 5700A supply common, B+5VCOM. This system is a complement to the CABLEOFF signal provided to the 5725A processor. Analog Input Switching Section 4-58. The analog input switching section is the primary analog interface with the 5700A output functions. Relay K108 serves exclusively to connect the output low lead of the 5725A to the load. Relay K106 does the same for the low sense line. Line MCOM, when switched to B-SENSE LO, serves as the low sense lead for the 5725A. Similarly, PACOM, which ties to the 5725A system ground VCOM at the power supply, is switched to B-PACOM, serving as the 5725A output low lead. Signal BOOST IN is the input high lead from the 5700A signal sources, and is switched from the inputs to the High Voltage Amplifier or Current Amplifier and sense amplifier by K107. Relay K101 also selects the proper source for the B-FEEDBACK signal. Signal B-FEEDBACK corresponds to the input high sense lead. Relay K111 provides the capability to provide local sensing directly by the 5700A on the 5725A High Voltage Sense assembly. Local sensing is used during ac voltage standby mode. This prevents the 5700A Oscillator from running without feedback when the 5725A High Voltage Amplifier assembly is in standby.

and its calibration circuitry by the 5700A. These switches are used only during calibration. Relays K105 and K109 are high voltage reed relays that provide output to the 5700A binding posts and remote sensing from the binding posts, respectively, during ac voltage operation. These connections are accomplished by connecting the output of the High Voltage Amplifier to B-OUT HI and the input of the sense amplifier to B-SENSE HI. Local sensing for standby and calibration is accomplished by K104, which enables the High Voltage Amplifier to drive the sense amplifier and its calibration circuitry directly. While 5700A current is sourced through the 5725A OUTPUT binding posts of the 5725A, relay K151 is energized to provide current guarding within the 5725A. 5700A output current comes to the High Voltage Sense assembly via J101 and is routed to a guarded coaxial cable through J152. The current return path is via E155. While 5700A current is sourced at its own binding posts, relay K151 is de-energized to prevent compromising of the 5700A internal guard. Control Section 4-59. The relay and switch control section consists simply of a pair of latched relay drivers, U157 and U158. Each of these latches receives its input from the microprocessor bus and drives a bank of relays. Additionally, the microprocessor has a ready means to quickly open all relays via a CLR signal that synchronously clears the driver latches. The outputs of relay driver U157 control six relays on the High Voltage Sense assembly (A6), four relays on the Interconnect assembly (A1), and four relays on the High Voltage Amplifier assembly (A3). Relays on the Interconnect and High Voltage Amplifier assemblies are controlled via HFPD, VLFPD, LFPD, and MFPD. Relay driver U158 is unique because all the high voltage relays connected directly to the outside world are driven from this latch. This provides a way for hardware to clear the instrument to a safe state independently of the microprocessor. This can happen in the following two ways: • Via the CABLEOFF signal that is asserted when the 5700A/5725A link is physically disabled as described under "Serial Interface/Guard Crossing Section". • By detecting an overcurrent condition in the high voltage power supply, which not only shuts down the high voltage supply, but also clears latch U158 via the signal HVCLR. Note that HVCLR, CABLEOFF, and CLR are diode-OR’ed to provide the composite clear function for U158. In addition to controlling all the high voltage relays, U158 also generates control line CLAMPD for the High Voltage Amplifier assembly, and HVSUPPLY* for the Power Supply and Digital assemblies. Comparator U150A provides level shifting of the output of the latch U158 so that the JFET switch Q104 can be controlled. Switch SW150 is simply a contact closure that indicates to the processor whether 5725A calibration is enabled.

Detailed Circuit Description 4 4-37 AC Line Voltage Selection Section 4-60. In addition to the primary power switch, S401, this section contains three line-voltage selection switches, S402 through S404. These three switches allow the 5725A to be set to eight nominal ac line voltage levels, each with a 10% tolerance. Thermistors RT401 and RT402 have negative temperature coefficients, and limit inrush current at power-up. Relay K401 provides a pair of shunt switches to bypass thermistors after about a half second. This allows greater efficiency than with thermistors alone, and the use of thermistors allows operation if the relay fails. CR401 through CR404 and C401 form an unregulated power supply that is not isolated from ac line power for controlling K401. R401, R402, and C402 provide a time delay that prevents Q401, and hence K401 from switching before the effective power supply capacitance is sufficiently charged. Metal Oxide Varistor RV401 prevents high voltage transients on the ac line from reaching the transformer by clamping voltages above 275V ac.

Title Page 5-1. Introduction ............................................................................................ 5-3 5-2. Where to Find Further Information........................................................ 5-3

Introduction 5 5-3 Introduction 5-1. The 5725A is calibrated at the factory before shipping. Calibration is traceable to the U.S. National Bureau of Standards. All that is required to maintain traceability is to run 5700A calibration to external standards at the beginning of the calibration cycle and do performance verification every two years. Calibration check and range calibration are optional procedures that are available for special needs. The 5725A is calibrated whenever an attached 5700A is calibrated. Where to Find Further Information 5-2. Information about 5700A calibration, and therefore 5725A calibration, is contained in the following sections of the 5700A manual set: • Section 7 of the 5700A Operator Manual presents procedures for calibration, calibration check, and range calibration. • Section 1 of the 5700A Operator Manual describes the calibration process and the theory behind its use to establish traceability to national standards. The same section includes a description of the calibration check feature, and suggests using it to develop a performance history for your 5700A. (This applies equally to a 5725A.) • Section 3 of the 5700A Service Manual contains a performance verification procedure recommended every two years to maintain traceability.