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РМ 2522
13
(In PM 2522 capacitor СІ is connected between the inputs of the comparator to obtain a better
series mode rejection).
The counting of pulses is realised in an up-down counter which is included in a MOS integrated
circuit. This circuit contains also:
- an input flip-flop (FF, described before)
- two analog switches (S) to switch the positive and negative reference voltage
- a polarity detector
a timer to control the measuring time
- a pulse output circuit which controls the 4-decade counter.
The latter circuit counts the pulses supplied by the ADC.
The number of counted pulses will be transferred to a memory, after which the counter will
be reset to zero by a reset pulse from the ADC.
А new measuring cycle can start now.
A multiplexer connects alternately each decade of the memory to the decoder-driver,
simultaneously a pulse arises to drive the anode switch of the corresponding seven segment
indicator
LED 5;
Via the decoder-driver the decoded number will be transferred to one of the 4-seven segment
indicator "LED's", the cathodes of which are switched in parallel.
Only that indicator,
the anode switch of which is closed, will light up.
As the switching speed is 512 times per second, it seems that all indicators light at the same
time.
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