Help for static power consumption measurement

A small series resistor is fine for low power devices - but you need a decent idea of the current drain profile under all circumstances.

A device that may draw 50mA statically may draw 2-3 (or more) amps on startup depending on circuitry - and the power system must still provide sufficient voltage. A series resistor of 1 ohm would be a liability in that case.

I would suggest iterating the sense resistor (which is as good a solution as any for a lab using 6 1/2 digit meters), starting with 0.1 ohm and watching the start transient. Note you have to watch out for the power rating so your sense resistor doesn't burn (or worse, burn

Obviously, the largest resistor that does not interfere with the power, the better the measurement (within reason :).

There are other solutions, including magnetically coupled clamps (which are non-inavasive), but they tend to be expensive and often have to be pre-calibrated.

Cheers

PeteS

But 2AAs in series have already 3V, (when 90% discharged 2V). That will probably be enough to run your device. Is it a PIC? What resistor you use is dependent on the current, for less than 100mA I would take 1R, above 0.1R with fresh batteries or better a bench supply it should be possible to determine the supply current.

In California, it's usually Volts times Amps.

(1) Ask the teacher what the f*ck he's asking for, or (2) Read that chapter of the textbook again.

You Betcha! ;-P