Hello all,
I want to measure how much current consume for a coin cell battery operated wireless sensor network, the expected range of current is below 10mA. Is it accurate to use the shunt resistor method for this type of measurement? or any best methods are available. If the shunt resistor method is a good way, how can I decide the resistor value, such that I can get accurate results?

Thank you
D.Vishnu

 

hi vis.
Do you have sensitive voltmeter capable of measuring millivolts.?
E

 

hi vis.
Do you have sensitive voltmeter capable of measuring millivolts.?
E

Hello ericgibbs,
Yes we are having voltmeter that capble of mesuring in mV.
We are thinking we will use oscilloscope to probe across resistor for measuring voltage.

 

hi,
If you used a1R shunt resistor in series with the high side of the battery output, a 10mA current will read 10mV across the 1R.
E
10mA = V/R = 0.01/1

 

Using 0.1Ω shunt resistor then V= I*R = 10mA * 0.1Ω = 0.001V = 1mV
What range of the shunt resistor that you should use, that is depends on the accurate voltage that you want as 1mV or 10mV.

 

If this is going to be a one time test I would use a commercial DMM (Digital Multi Meter) with a low DC current range placed in series with your load. Just as an example a basic Fluke 87 DMM has a 40 mA DC current range and offers 0.01 mA resolution and an uncertainty of ±(0.2% + 2). You make no mention of the resolution or measurement uncertainty you desire? While you can use a shunt the signal off the shunt will be a very low DC voltage which will likely need filtering for noise and amplification.

Ron