Measuring a micro-V signal change in a millivolts DC signal

Thread Starter


Joined Jun 30, 2020
Hi everyone!
New poster here.

I am working on a project where I have a ~10 milli-volts DC signal from an on chip resistor, and I want to be able to read a 7 micro -volts change in signal from it. I know measuring 7 micro-volts can be hard, but the benchtop DMM I am using, Agilent 34401A, has that resolution, and can generally measure with a 1 micro-volt resolution provided there is not noise in the set up.
My current set up is a four wire measurement across the 10 Ohm on chip resistor, and I am using benchtop instruments to do that. I connect to the device using triax cables, adapters, and wires. My current source is a DC 1 milli amps to the 10 Ohm resistor (I cannot increase current due to device limitations), I measure the voltage across the biased resistor with the DMM.

The noise of my current benchtop set up/chip device varies bw ~10 - 100 micro-Volts. I can sometimes get it down to 10 micro-Volts pk-pk (with help of faraday cage and proper grounding) but not better than that.

If I need to measure a 7 micro-V change in signal with this noise, what is my best bet at the moment?
Should I move everything on board, and read the voltage with an on board ADC+microcontroller? Will that reduce the noise in the milli-volts signal? Has anyone here ever measured uV signal change from a mV DC signal? What is the general consensus about low signal uV measurements? On board microcontrollers? I am concerned that if the noise source is not my open connections and wires, but my actual chip, then even measuring my signal on board will not help.

My other option exciting the resistor with an AC current, and moving my voltage signal to a higher frequency where there is less noise.

Thanks a lot, I appreciate any direction at all!