The below Details from Datasheet - These pins are used in
this circuit to Autorange the DPM with some peripheral CMOS
"OVERRANGE (Pin 27)
This pin goes positive when the input signal exceeds the range (20,000) of the converter. The output F/F is set at the end of BUSY and is reset to zero at the beginning of reference integrate in the next measurement cycle.
UNDERRANGE (Pin 28)
This pin goes positive when the reading is 9% of range or
less. The output F/F is set at the end of BUSY (if the new
reading is 1800 or less) and is reset at the beginning of
signal integrate of the next reading."
The Range is Defined by QB and QC of 4029, there are four
ranges. The two bit Code from this can control the decadic
range of an Attenuator or Amplifier.
This may be Slow Responding, There may be minor errors in the
circuit documentation, but it is a product that worked and was
used in some applications.
ICL7135 Pin 11 +5V, Pin 1 -5V, Pin 24, digital GND, add a
decoupling 104 CD, cap from +5 to GND and -5 to GND.
20th Mar 2020
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