To give some back ground I am a technician working on the code for this
beast and I didn't design the circuit. So my questions may seem simple.


Spehro Pefhany Wrote:

>Are you trying to measure the voltage across the 1K resistor? That's
>REALLY not feasible, your whole signal will be lost by a 100ppm
mismatch
>between the 100M resistors, and if you wanted 10% accuracy, you'd need
>them to match and track within +/-10ppm. That's just not going to
happen
>at that resistance level.


So the mismatch in resistance is drowning out my measurement, and it
can't be accounted for as an offset?
So what type of tolerance would that be to get it to work?

>Howzabout you put the 10K in the TP10 to ground net and measure the
>voltage across that? Add some protection in case the output gets
>shorted you don't lose the op-amp etc. every time.

So it will not work as it is done now? My boss designed this baby, if
his design won't work how should I tell him and convince him it won't
work?

P.S This is my first job out of college. And thanks for all the help.

Chuck

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