Measure 60mVpp with +/- 0.1mVpp

[PaulBarr]

I have a signal that is  60mVpp AC. I want to measure the Vrms in LabView. What hardware could I use for this if I am  trying to detect a change as small as 0.1mVpp.

[Dennis_Knutson]

There are more signal properties that need to be provided as well as form factor. You can browse the products (link at the top of the page ) or contact your local Sales Engineer.

[James-B]

Dennis is right, but take a look at the NI PCIe-6320.  It should fit your application.

[Now_With_Underscores]

This additional information will help us narrow down the options:

-sample rate

-do you need accuracy or precision?  Sounds like precision ('detect a change'), but just making sure

NI's standard E/M/X series 'DAQ' cards likely won't get you 100uV accuracy (not to be confused with resolution).  

My first recommendation is a DSA card, such as the PXI-4461, or the NI-4071 DMM.  I can make a much more informed decision with more information.

[Henrik_Volkers]

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@Now_With_Underscores wrote:

This additional information will help us narrow down the options:

-sample rate

-do you need accuracy or precision?  Sounds like precision ('detect a change'), but just making sure

NI's standard E/M/X series 'DAQ' cards likely won't get you 100uV accuracy (not to be confused with resolution).  

My first recommendation is a DSA card, such as the PXI-4461, or the NI-4071 DMM.  I can make a much more informed decision with more information.

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Sorry,

here is the spec of the 6251 (M?) DAQ

I would expect that you can measure a 60mVrms AC signal in the +-100mV range  and do better than 1100ppm absolute accuracy 🙂

But if the poster can give more information on frequency range , surrounding conditions (Lab, industrial , outdoor,..) , traceability, number of channels etc. there would make a difference in spending 600 or 10k $Unit 😉

BTW: 60mV AC in audio range with 0.1% relative change can be done with the line audio input of the soundcard 😄

[Now_With_Underscores]

Hey Henrik, yes, the 6251 is an M series DAQ device.

Let's talk specs ;)...

If you read all the fine print, you'll need to average 100 samples to achieve the specified uncertainty.  You'll also need to stay very close to the external and internal self-cal temperatures, as those add uncertainty very quickly as temperature changes.  Assuming you stay within ±5°C of external and internal self cal, AND you average 100 samples, then yes, you can achieve 83.7uV* uncertainty in the 100mV range with a 60mV reading. 

However, if our mutual comrade is looking for 100uV uncertainty, then I propose that 83.7uV uncertainty is not enough; typically, we want 4x less uncertainty on the measuring equipment.

If our mutual comrade is most interested in precision, then I propose looking at any of the various DSA cards (4431, 498x, 446x, etc).  If we look at the 4461, we can see that our gain error is much smaller. 

Overall, I agree we need more information from our customer.

Have a great day

*Using equation in spec sheet:

60E-3*(150E.6+13E-6*5+1E-6*5)+100E-3*(150E-6+90E-6)+15E-6*3/sqrt(100)=83.7uV