Thermo Scientific RO-20 Operating Manual

I: clearing improvement A: substantial amendment Explanations must be given, at least with Category A. ...

1.2 Measuring Units..................................................................................................................... 1-2 1.3 Detector Specifications.................................... ...

2.3.1 Checking the Zero Setting .............................................................................................. 2-2 2.3.2 Minimizing Deflection ................................................................................................... 2-2 2.3.3 Ion Chamber .............................. ...

Figure 1-1: Model RO-20 Ion Chamber............................................................................................... 1-1 Figure 1-2: Nominal photon energy response ...................................................................................... 1-3 Figure 3-1: Connector / battery board component layout .................................................................... 3-1 Figure 3-2: Basic operation of the cir ...

detect beta ( ß ), gamma (γ) and x-ray radiation. The RO-20 has five linear ranges of operation to measure exposure rate for x-ray and gamma radiation. The ion chamber is vented to atmospheric pressure. The RO-20 is calibrated to γ radiation (137Cs). A single rotary Function Switc ...

The ranges are 50 R/h,5 R/h and 500mR/h,50mR/h,5 mR/h. The RO-20 chamber is designed to have a flat energy response in roentgen units. Use the procedure given in this manual for calibration of the instrument. The calibration controls on the main circuit board are marked from 5 through 50 k, which corresponds to the 5 ranges (expressed in R ...

slide facing the source. • ±30% from 8 keV to 1.3 MeV, with the open slide facing the source. • ±15% from 33 keV to 1.3 MeV, with the closed slide facing the source. • ±15% from 55 keV to 1.3 MeV, through the side of the instrument. 1.3.8 Examples of Beta Response • Uranium slab: 30% of true mrad/h field behind 7 ...

• 0–5 mR/h • 0–50 mR/h • 0–500 mR/h • 0–5 R/h • 0–50 R/h 1.4.2 Meter • Scale length: Approx. 3 in. (7.6 cm) • 2% accuracy. • Linear markings: From 0 to 5 in 50 minor increments. • Back-lighted. 1.4.3 Response Time Five seconds, 0 to 90% of final reading. 1.4.4 Linearity • Within ± 5% of full scale • Battery Dependence (Wi ...

1.4.5.2 Internal • Five calibration controls, one for each range. 1.4.6 Batteries • Main power: Five AA cells. • Chamber bias: 3 ea 12V alkaline batteries = 36V. • Life: AA cells, widely variable according to RO-20 usage and battery type. • Typical alkaline: mR/h ranges, 2500 hrs; all other positions, 130 hrs. • 36 Volt chamber bias battery life: Totally dependent upo ...

1.4.7.6 Size 4.2 in. wide x 7.9 in. long x 7.7 in. high (10.7 cm x 20.1 cm x 19.6 cm), including handle. ...

2.1.1 Function Switch The function switch is a nine-position rotary switch that turns the instrument off, checks the condition of the batteries, checks instrument zero, and selects the range of operation to be used. 2.1.2 Zero Knob The Zero Knob is used to set the meter to zero when the Zero position of the Function Switch is selected or when the detector is not in a signif ...

2.3.1 Checking the Zero Setting The zero setting of the RO-20 may be checked in any radiation field by selecting the Zero position of the Function Switch. If a minor offset from zero exists on the most sensitive range when in a known insignificant field, the Zero Knob may be used to remove the offset. Zero need not be reset when using the higher ranges. 2.3.2 Minimizing Deflection When ...

Altitude When Calibrated Sea level (ft) 1000' 2000' 3000' 4000' 5000' 6000' 7000' 8000' 9000' 10,000' Sea level (ft) 1 0.96 0.93 0.90 0.86 0.83 0.80 0.77 0.74 0.71 0.69 1000' 1.04 1 0.96 0.93 0.90 0.86 0.83 0.80 0.77 0.74 0.71 2000' 1.08 1.04 1 0.96 0.93 0.89 0.86 0.83 0.80 0.77 0.74 3000' 1.12 1.08 1.04 1 0.96 0.93 0.89 0.86 0.83 0.80 0.77 4000' 1.16 1.12 1.08 1.04 1 0. ...

Altitude When Calibrated Sea level (m) 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 Sea level (m) 1 0.97 0.94 0.91 0.89 0.86 0.83 0.81 0.78 0.76 0.73 0.72 0.69 0.67 250 1.03 1 0.97 0.94 0.91 0.89 0.86 0.83 0.81 0.78 0.76 0.74 0.72 0.69 500 1.06 1.03 1 0.97 0.94 0.91 0.89 0.86 0.83 0.81 0.78 0.76 0.74 0.72 750 1.10 1.06 1.03 1 0.97 0.94 0.91 0.89 0.86 0 ...

3.1 General Theory Figure 3-1 and Figure 3-2 show the basic operation of the circuit. The ion chamber structure is maintained at chassis potential while all the other circuitry is held at –36 volts by the 3 ea 12- volt bias batteries. When the air in the chamber ionizes due to radiation, a minute current flows from the chamber wall to the center electrode, causing the minus input lead of t ...

3.2 Functional Theory 3.2.1 Ion Chamber The ion chamber is located inside the case below the meter. It consists of the lower two inches of the 3-in.-diam chamber assembly. The remainder of the volume contains electronic components. The chamber wall is 0.20 in. (0.51 cm) thick conductive plastic, and the face is one-mil (25 micron) aluminized Mylar. Another one-mil Mylar l ...

The amount of ion current produced depends upon the intensity of the radiation field and the density of the air in the chamber. The density depends on the temperature and pressure of the air. A temperature- sensing compensation circuit corrects for the change in ion current due to temperature changes, leaving only the pres ...

When operating on the two R/h ranges, K102 is pulled in to place R102, the 1.5-gigohm resistor, in the circuit. The higher ion currents develop sufficient voltages for operation with this smaller resistor. When using the mR/h ranges, both relays are open, leaving R101 (the 150-gigohm resistor) as the feedback element. The feedback signal to the two high- value resistors comes ...