At 04:07 PM 9/10/2004 -0700, you wrote:
>Jumped into this a little late so forgive my ignorance of the thread.
>
>If you want to build a nanoammeter, why not use a decent FET opamp to
>buffer the input to your multimeter, measuring a largish-value shunt
>resistor?
>
>Accuracy +-5% shouldn't be too hard to get.
>
>-Bob

Or just use the multimeter on low volts range with a resistor. Most of
them use a variant of the 7106 chip which has a typical input current
of 1pA (10pA maximum). On the 200mV range there are usually no resistors
shunting the input. So, using a 1M 1% resistor will give you 100pA,
resolution, 200nA full scale, and typically better than 1% accuracy (with
a low-end 3.5 digit DVM).

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com




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