Well, it's at a 1mA test current (I'm assuming a 4 point probe to mitigate contact resistance) so 10u Ohm would give a 10nV DC signal. That's a pretty small voltage signal and comparable to a fairly standard chopper stabilized instrumentation amp rms noise at room temp near DC.
I'm not sure whether higher currents are all that reasonable. Cooling the precision amp is an option to reduce the noise figure, but at that point you'll want optical isolation and battery supply too.
Thanks! That's great information. We had to make our own, but it's good to see that there are decent off the shelf systems. I agree that contact resistance on these tiny samples has got to be a huge issue (can they use mercury?). However, what I've seen suggests that even the low frequency AC measurements are more complex due to capacitive coupling effects. However, narrow bandwidth lock=in should improve noise... the equipment still just claims 10u Ohm.
I'm not sure whether higher currents are all that reasonable. Cooling the precision amp is an option to reduce the noise figure, but at that point you'll want optical isolation and battery supply too.
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