Indicator Circuit

TM 11-6665-209-40

b. Indicator Circuit. The indicator circuit consists of capacitor C110, resistor R 1 3 0

a n d micrometer M101. Meter M101 and resistor R130, in series, are connected in

parallel with the capacitor. The complete circuit is connected between the plate of V 1 0 4

in the pulse-shaper and amplifier circuit and the V104 plate supply. When V104 conducts,

the current pulse charges C110 and causes a meter deflection. During the interpulse in-

terval, V104 is cut-off, and C110 discharges through R130 and M101. This condition

keeps the meter deflection nearly constant.

(1) The function of the indicator

circuit is to convert the output

pulses from V104 into a

relatively steady meter deflec-

tion. This deflection is propor-

t i o n a l to the radiation intensi-

ty. The pulsed output of V104

is smoothed and averaged by

C110 and R130 to form a

steady meter current. The

a v e r a g e current through the

meter depends upon the

f o l l o w i n g factors:

The number of pulses per

second received from V104.

The amplitude and duration

of each pulse.

(2) S i n c e the number of pulses

p e r second is proportional to

the radiation intensity, the

a v e r a g e meter current will be

p r o p o r t i o n a l to the radiation

intensity as long as the

amplitude and duration of

each pulse remains the same.

(3) When the range is changed through switch S102, the duration of the pulses

changes. Therefore, the meter current pulse per second also changes. This

current is proportional to the number of pulses per second. The number of

pulses per second is, in turn, proportional to the radiation intensity for a given

type of radiation. The meter scale can thus be calibrated to indicate milliroen-

tgens per hour (mR/hr) directly.

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