current measurement using CRO

[Kick]

Hiii all

I am trying to do measuring current in my circuit using CRO. Circuit is 3V battery powered and current would be uA to 1mA range. I connected a series resistor with battery for voltage measurement across it. Tried 1K,10K and 100K resistors,but voltage is dropping below 2V. Circuit required min.2.1V for working. Did I do any mistake in the measuring method?? also I am not much familiar with CRO.


Battery side (2.9V) -------Resistor(1K/10K/100K)---------- Circuit side <2V.

 

[srizbf]

select a resistor for current measurement such that the voltage drop across it is reasonable.
say , 100 to 200mV in this case.

 

[FvM]

Sounds like you are trying to measure µC supply current.

1. You'll use a series resistor with suffcient margin to minimal voltage, e.g. 100 or 200 ohm.
2. You can't display µA to mA current in a linear range. I'm not sure if it makes sense at all to acquire current waveforms in the µA range. You're mostly interested in knowing the average current which can be measured with a multimeter, possibly using a low-pass filter.
3. To see current waveforms in the µA range, you'll either use an amplifier or a shunt with parallel schottky-diode.