throbscottle
Well-Known Member
I finally worked out how to get around the need to tie one in-amp input to ground for my 4 wire resistance circuit, by replacing the ground connection with the output of an inverting buffer. So now the voltage across the DUT is differential, much better.
The resistors and op-amp choices are fairly arbitrary since this is just proof of concept.
U2 is just a standard ohms to volts converter, the output of U1 replaces ground, U3 is a buffer to stop the inverter stealing away the measurement current, U4 provides the 4 wire measurement, provided by R10 and R11.
Ok so there's another op-amp input competing for the measurement current now, but apart from that I think it's good.
Just fishing for comments...
Cheers
The resistors and op-amp choices are fairly arbitrary since this is just proof of concept.
U2 is just a standard ohms to volts converter, the output of U1 replaces ground, U3 is a buffer to stop the inverter stealing away the measurement current, U4 provides the 4 wire measurement, provided by R10 and R11.
Ok so there's another op-amp input competing for the measurement current now, but apart from that I think it's good.
Just fishing for comments...
Cheers