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measuring nanoampere current using milliammeter

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pragash

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dear friends,
here , i have to measure current across a resistor which is in nanoampere but I’ve only miliammeter with me. Can anybody help me advice on this?
 

This is not so simple..your multimeter input impedance is somewhere in MΩ range so the input will very comfortably "eat" this current ..
You will need a good quality instrumentation amplifier to buffer and amplify this signal and then, and only then, you will be able to measure nanoamps..
Regards,
IanP
 

you should precision "JFET" ins. amplifier
analog device and texas has.
Regards.
 

First of all, check out this:
See my reply there.

Or, you can try the circuits in these National appnotes: Fig. 9 in AN-71 www.national.com/an/AN/AN-71.pdf
Fig. 11 and Fig. 12 in AN-242 www.national.com/an/AN/AN-242.pdf

You can experiment with other opamps, too. The point is that the input current and offset voltage should be as low as possible and drift as little as possible.
 

if the resistance is large, you can measure the voltage across the resistor and just try to compute for the current.
 

you can use a high impedance amplifier to amplify

the voltage signal between the resistor, then you can

use a general DVM to measure the output voltage

and calculate the current in the resistor.


best regards





pragash said:
dear friends,
here , i have to measure current across a resistor which is in nanoampere but I’ve only miliammeter with me. Can anybody help me advice on this?
Click to expand...
 

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