PCI-6733 signal noise when Computer Monitor is plugged in, weight on case

[Tall_Michael]

Greetings,

I hope this is in the correct section.

Card: PCI-6733

I am getting a 60Hz, 2mV peak to peak noise with a 2.4mV offset when the monitor is plugged into the VGA port.

Same card in a second computer, problem is worse, 4mV peak to peak, 4.3mV offset. When I push on the case near the power supply the offset goes up a couple millivolts.

Both computers run the exact same versions of software and drivers. Both Dell, and pretty similar to each other in specs and hardware.

I have a third computer that the noise coming out of the card is horrible no matter what.

I swap cards and the problem stays with the computer, does not track the acquisition cards.

Any idea how to fix this and what is causing this?

Thanks for any thoughts!

-Michael

[Trey_C · Accepted solution]

Tall_Michael,

It sounds like you may be plugging your monitor and your PC into different outlets.  If this is the case, it is likely the cause of your noise and can be eliminated by plugging both devices into the same power outlet.

Here are a few articles that discuss the noise you are experiencing and different work arounds in case what I mentioned above is not the case:

Measuring Grounded Signal Sources

How Do I Eliminate Powerline Noise from DC Measurements Without Using a Hardware Low-pass Filter?

I hope this helps!

Thanks,

Trey C.

[Tall_Michael]

Trey C.,

Thanks for the reply. I made certain all systems were plugged into the same outlet, and they are now. It helped a bit with the noise, thank you!

The rest of the noise I am working on fixing, but it seems to be that there was a lot of cords wrapped around eachother, and as one is the signal line out from a high voltage amplifier that was also causing some issues. The 60Hz is still somewhat apaprent, and I can't average it out as I am measuring signals from 100Hz to 1kHz.

So, general solution was to plug everything in to a common socket and make sure there was no noise traveling from wrapped cords.

Thanks again!