Hi,
Please could someone point me in the right direction to understand this circuit. From what I can fathom it's an Op Amp Integrator. The circuit is powered by 4 x AA batteries and is used to feed an A/D port on a CPU for the purpose of monitoring the battery voltage. There are two resistors, R2 and R3. R2 appears to be a constant value of 143K. R3 however, varies from circuit to circuit and sits between two test pins - TP1 and TP2. I am guessing that R3 is somehow selected to calibrate each individual circuit so the input to the A/D converter is accurate. If this sounds about right, I'm curious how the value of R3 might be selected and what parameter might be measured in order to determine what value R3 should be?
Any advice, gratefully received.