On 8/10/2011 6:24 PM, IVP wrote:

> Just read an article about a DMM adapter using the MAX4239ASA+
> chopper amp. 0.1uV offset typical, 2.5uV over the temperature range.
>
> Article claims resolution of 10pA on a 4.5 digit meter, 0.2%
> accuracy
>
> Unfortunately the circuit is not bidirectional
>

I think it is... that's the reason for the "synthetic" ground.  The=20
ground opamp splits the 3V battery into +/- 1.5V rails and since the=20
input is referred to ground it can go both ways, no?
--=20
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