What is the minimum voltage change I can measure with a 6.5-digit multimeter?

Least significant digit of 6.5 digit meter in 1 V range is 1 uV. Thus you can't detect 100 nV change, even if noise is only 30 nV.

Page 146 will give you means to get to total error :



Regards, Dana.

I think, OP is asking about resolution (e.g. minimal detectable difference of readings), not total error.

Thank you very much for the answers. Yes, I am asking about resolution. I collect data via PC, and the multimeter provides readings with much higher digits down to the 1 nV range. I'm not sure if these readings are accurate.

@strahd_von_zarovich, is your concern absolute accuracy or just resolution ? I see
prior post ultimate concern is accuracy ?




Regards, Dana.

danadakk said:

@strahd_von_zarovich, is your concern absolute accuracy or just resolution ? I see
prior post ultimate concern is accuracy ?

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Regards, Dana.

Click to expand...

Dear Dana,

Just resolution. My main goal is to measure changes rather than absolute accuracy.

For example, if I measure 0.100,000,000 V and then increase the source voltage by 50 nV, I want to measure 0.100,000,050 V. -

As long as I can measure the change correctly, I don't really care about the actual values.

O.k., PC interface provides higher resolution. Presumed specified 0.03 ppm of FSK noise at PLC = 100 applies also to 1V DC range, then useable resolution of measurement depends on expected significance. According to user manual a resolution of 2*Vnoise,rms is obtained with 4.5 % prohability of failure, 3*Vnoise,rms is obtained with 0.3 %.

Hi,

Thank you very much for the answers. Yes, I am asking about resolution. I collect data via PC, and the multimeter provides readings with much higher digits down to the 1 nV range. I'm not sure if these readings are accurate.

Click to expand...

from my experience: everything below 10uV becomes difficult.

Depending on range, frequency response, measurement timing ... and so on one could go quite below 1uV .. But I see no change to get below 100nV with reasonable effort.

For example, if I measure 0.100,000,000 V and then increase the source voltage by 50 nV, I want to measure 0.100,000,050 V. -

Click to expand...

This is 0.5ppm? it´s difficult to detect from 0nV to 50nV ...(without 100mV offset) but in the rane you say .. even the REFERENCE and it´s drift plays a major role.
Noise, thermcouple effects, mechanical stress on a PCB ... all will cause more error than 50nV.

Again: it all depends on the complete specifications.

Klaus

An excellent reference for low level measurement's, attached.