Test and Measurement Forum

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 it’s about 1Mohm but I could do with a few decimal places on that.

Thanks in advance

Rob

I should have pointed out that I need to know the impedance of my ADC-16, not any old generic value.

Thanks

Ok, update for you, me, er... (ever get the feeling you're talking to yourself?)

I have used another multimeter (high quality) to measure the impedance of the ADC-16. It worked! (after a fashion).

The problem I have now is that the multimeter outputs 1.01V (as can be seen in the PicoLog software) to make the measurement, this means that I have measured the impedance of the logger's 1V range, does the ADC-16 have multiple ranges? Is it autoranging? (I would imagine so)

If this is the case I can "force" the ADC-16 into the appropriate range by placing a known (very) large resistor in series with the ADC-16 but this makes the measurement a little more... unstable, and it's hard to get an accurate reading.

I hope this simplifies the question, basically I need to know if the ADC-16 has multiple range, and if so, what are they?

Thanks

Rob

Hello Rob,

Thank you for your posts.

The input range is fixed at ±2.5v, there is no autoranging included.

If you are writing your own software, you will find this information in the product manuals.

Best regards,
Michael

Perfect!

Thanks for your reply Michael.

Best regards

Rob