White noise in Audio Input - MyDAQ

[robert_ugo]

Hello,

I have a problem with acquiring sound from any source (laptop, mp3s). When audio cable is disconnected from source the Vp-p is about 1mV (its normal i think). Screenshot:

But after plugging cable to source (without playing any music) some kind of white noise show up.

Screenshot:

It's very annoying. Is there any solution for that?

[PrimaryKey]

Hi robert_ugo,

we don't know if there is a solution because we still don't know what the problem is. WHat kind of source of signal do you have? maybe the problem is not the measurement device ( it doesn't seem to have noise on the 1 screen) but the source itself. Can you please try to use other sources of signal and measure what is the difference between readings?

Happy holidays

[ValkoA]

Hi Robert!

As the previous post had said, it would be beneficial for solving this problem to have further informaition about what kind of source you are using, how the connection layout looks and so on.

On the information you've described so far, I'm assuming you're using a laptop, so most likely a headphone output to generate sound for the myDAQ device. In that case, the most likely culprit is a Ground Loop. You can test for this very easily, just disconnect the laptop from the power supply. If this stops the noise, then you can be sure it's a ground loop.

To avoid ground loop noise, use differential measurements, double insulated power supplies or some other form of separating ground signal levels. See this whitepaper for more information.

Kind regards:

Andrew Valko

National Instruments