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Designing an Ohm Meter

J

John Larkin

Jan 1, 1970
0
It does? Maybe since you defined Vr=Vs-Vx and hide it from yourself it
seems that way, but Vs is still there....


It's there, but doesn't afect the results as long as it's short-term
stable. Of course, you *do* have to accept Ohm's Law for the duration.

I assumed that a pic would only digitize ground-referenced voltages,
hence the path through the math. When I do this, I usually use a fully
differential adc, so I can measure the voltage across each resistor
directly, which has the advantage of ignoring any lead resistances.

John
 
M

MooseFET

Jan 1, 1970
0
On May 12, 10:07 am, John Larkin
[....]
I assumed that a pic would only digitize ground-referenced voltages,
hence the path through the math. When I do this, I usually use a fully
differential adc, so I can measure the voltage across each resistor
directly, which has the advantage of ignoring any lead resistances.


You could float the PIC in mid air. It wouldn't mind. They draw a
low current that Vcc and Gnd can be provided by an op-amp.
 
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