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µV-measurements:Noise using pre-amplifier or 24Bit ADC?

Question asked by Alexxx on Nov 22, 2017
Latest reply on Nov 23, 2017 by JellenieR

I want to do high resolution µOhm measurement with a battery powered, small device.

So differential voltages below 50µV should be measured fairly slow (0,1 sec. - 1 sec.)
The noise-free resolution should be < 1µV.
I thought of using 4-wire connection and doing current-chopping with full-bridge-mosfets
and using a shunt resistor for creating Uref-ADC...

 

My questions now are:
Which design gives lower overall noise level?
 - a slow high precision and resoloution ADC (>= 24Bit) directly without pre-amplifier, or

- a ultra-low-noise (/ zero-drift) pre-amplifier with a 16Bit-ADC?

 

Doesn't a pre-amplifier with 200nVpp 0,1...10Hz-noise give better performance than an ADC with 200nVrms ?

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