the output of PXIe-4322 have some problems

[caijin]

Dear engineer：

I am Jin Cai, a member of ultra-cold atoms laboratory in USTC. We have bought six PXIe-4322 modules with one PXIe-8840. But there are some problems. The instructions says that the RMS of the noise ranging from 10Hz to 20MHz should be about 500 μV. However, the real noise we have measured is twice as much as what it should be. I doubt that there is a problem with your product. Moreover, we have used a spectrum analyzer to analysis the output of PXIe-4322 when it is in the power state and we find some high-frequency noise. This abnormal noise is higher than 80MHz. The electromagnetic environment is very clear in our laboratory, so the noise is likely to be produced by the PXIe-4322 itself.

I have asked Chinese Branch of NI for help, but their suggestions make no sense. It is disappointing, you know. As a loyal customer, our laboratory trusts the engineers and technicians of NI, believes that you can supply excellent products that suit for our needs. I am looking forward to your detailed reply!

[Qiu333]

Hi, mate,

The specification file you find from NI official website are usually less than the performance of real products. That is what NI usually do. You can hardly tell if a circumstance is quite and nice with your eyes. But your lab is better than any other labs because you did not get a very large noise there, though a little bit higher than the noise shown in handbook. 

When you search for 'noise' on NI forum, you will get a lot of topics that talks about the same problem. Also, you can find exactly the same story in other company that produces instruments.

As for your question, The noise of 4322 you find from handbook is the noise of the card itself. It is not concerned with your PXIe chassis, controller and electric supply etc.

You mentioned about the high frequency noise, but did not show the power of it. So how much power density in dBm did you get?

All in all, what are you using 4322 for? Does this noise really influences your data acquisition? Maybe there is some method to reduce the influence of it.