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I want to measure the stand-by current of the PIC, but my DVM has minimum 2000micro (u) amper switch. It shows 0 micro amps when in 2000 u amps mode. Without building circuit a complex (more than 3-4 components) circuit, how can I measure nano amps?

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Put a suitable resistor in series, and your DVM (in voltage mode) over the resistor.

For instance, a current of 100 nA through a 1M resistor will give you 0.1V. Check the input impedance of your DVM, for this to work it must be >> 1M. You will probably need a switch to short the resistor for the period that your target is not yet in low-power mode.

Another way would be to use a known-sized capacitor as power supply and see how fast it discharges. Again, your measurement instrument must have a high impedance, otherwise it will disturb the measurement. You might get around this by connecting the voltmeter to measure the voltage only at specific moments.

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    \$\begingroup\$ I think it safe to say "You will need a switch to short the resistor . . ." \$\endgroup\$ Jan 24, 2015 at 12:00
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    \$\begingroup\$ If you know the input impedance of your multimeter, you may not even need a separate resistor. Just stick the DMM in series, in voltage mode. \$\endgroup\$ Jan 25, 2015 at 5:30
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Get one of those: https://www.kickstarter.com/projects/eevblog/current-gold-precision-multimeter-current-adapter. It has also been reviewed on the EEVBlog.

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    \$\begingroup\$ It was made by the EEVBlog guy!!! \$\endgroup\$ Jan 24, 2015 at 12:46
  • \$\begingroup\$ I've watched his videos on low current measurements ... wish I had known how to do it 10 years ago ... \$\endgroup\$
    – Spoon
    Jan 24, 2015 at 20:32
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TIA opamp circuit with a FET opamp.
opa134 has ~pA of bias current.
10-100 Meg ohm feedback resistor.
Bipolar power supply.

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