Rich Grise wrote:
On Tue, 06 Mar 2007 19:06:50 +0000, Robert Baer wrote:

MassiveProng wrote:

On Mon, 05 Mar 2007 20:27:02 GMT, ehsjr Gave


I don't know what your meter does. I assume it's like any other. If so,
it uses a shunt and develops a voltage across the shunt so it is the
same principle as what I'm taking about, but not the same values. AFAIK,
they don't use a megohm neighborhood shunt for low current - but then, I
don't have any meters with an nA scale.

They don't. It is a precision, low value shunt resistor, and they
read voltage across it to determine the current through it.

And that is *exactly* what i proposed with the "trick"; place the DVM
on the 200mVFS scale, add a shunt 1.11Meg resistor (that means in
parallel; use the dictionary) across the meter and the sensitivity of this
network is 200nAFS.
Simple ohms law...


And cover everything in the lab with aluminum foil, so your body
capacitance doesn't zap your meter first time out. ;-)

Cheers!
Rich

Why?
I made that shunt box and use it on occasions where i need to measure
low currents, and have seen no problems whether i use it with my 3.5
digit DMM or my 4.5 digit DMM.