RADIAC SET BLOCK DIAGRAM ANALYSIS

TM 11-6665-209-40

C The power supply also furnishes regulated DC plate voltage to the amplifier and

pulse-shaping tubes V103 and V104 and also supplies these tubes with 1.2V AC filament

voltage.

D The G-M tubes generate voltage pulses when exposed to radioactivity. The

average repetition rate of these pulses is proportional to the average radiation field inten-

sity in the vicinity of these tubes. This rate is used in the radiac set to measure the

radiation intensity.

E The pulses generated in the G-M tubes are of random amplitude and random

duration and are fed to the pulse-shaper circuit and amplifier. This circuit is a one-shot

m u l t i v i b r a t o r which is substantially independent of incoming pulse amplitude, converts

the original pulses into pulses of equal width and feeds them to the indicator circuit.

The width of these pulses is controlled for each sensitivity range by the appropriate

calibration potentiometer.

F The indicator circuit converts the pulses fed from the pulse-shaper and amplifier

circuit into a meter reading that is proportional to the pulse repetition rate. The propor-

tionality factor depends on the sensitivity range selected by means of the range switch.

The meter scale is changed automatically when the sensitivity range of the radiac set is

changed by resetting the range switch. Thus the meter is always direct-reading.

G The voltage-regulator circuit keeps the plate voltage of the amplifier and pulse-

shaper circuit constant as the battery voltage decreases with age.

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