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

[strahd_von_zarovich]

Hi everyone,

I am testing a very sensitive analog circuit, and I am unsure if I am measuring the values correctly.

The resolution of the multimeter is crucial for me. I need to measure changes of 100nV.

Can I do this with a 6.5-digit multimeter? My multimeter model is the Agilent 34411A. According to the datasheet, the resolution is given as 0.03 ppm in the 10V range and 100 nplc. So, I concluded that I can measure a voltage change of 30nV in 1V range. Is this correct?

Here is the relevant part of the datasheet:

 

[FvM]

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.

 

[danadakk]

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

L4411A/34410A/11A Digital Multimeter User's Guide

34410-90001; Edition 5. Quick start chapter, features and functions, remote interface configuration, measurement tutorial and product specifications.

www.keysight.com

Regards, Dana.

 

[FvM]

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

 

[strahd_von_zarovich]

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.

 

[danadakk]

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

ADC Accuracy Part 1: Is accuracy different from resolution?

This technical article was updated on July 23, 2020. In talking to system designers using analog-to-digital converters (ADCs), one of the most common questions that I hear is: “Is your 16-bit ADC also 16-bit accurate?” The answer to thi...

e2e.ti.com

Resolution vs Accuracy vs Sensitivity Cutting Through the Confusion

This article is part of TechXchange: Why Low Iq is the Smart Thing to DoWhen selecting an analog-to-digital (A/D) board, an external data acquisition system, or other measurement...

www.electronicdesign.com

Regards, Dana.

 

[strahd_von_zarovich]

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

ADC Accuracy Part 1: Is accuracy different from resolution?

This technical article was updated on July 23, 2020. In talking to system designers using analog-to-digital converters (ADCs), one of the most common questions that I hear is: “Is your 16-bit ADC also 16-bit accurate?” The answer to thi...

e2e.ti.com

Resolution vs Accuracy vs Sensitivity Cutting Through the Confusion

This article is part of TechXchange: Why Low Iq is the Smart Thing to DoWhen selecting an analog-to-digital (A/D) board, an external data acquisition system, or other measurement...

www.electronicdesign.com

Regards, Dana.

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.

 

[FvM]

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 %.

 

[KlausST]

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.

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. -

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