Hi

Background:

I'm using and ADC-16 to measure a voltage drop across a low value resistor (0.25 ohms). This resistor is in series along the return line from a product to its battery.

I use a calculated parameter to show the current, log that for around 1/2 an hour, then (using excel) integrate current over time intervals to get instantaneous charge, sum the charges and divide by total time to get average current. (Simple, eh?!?!)

Problem:

I need to measure the 'off' (or Standby) current of the product, typically nano-amps, but the drop across the resistor is not enough to be seen by the logger.

Attempted solutions:

A previous solution was to put the data-logger in series (instead of the low value resistor) but the impedance needs to be known. (Previously an ADC-42 was used, this is no longer available and attempts to measure the impedance of the adc-16 have yielded dubious results). I know itâ€™s about 1Mohm but I could do with a few decimal places on that.

Thanks in advance

Rob