Data acquisition with NI 9234

[claudio_gerosa]

Hi, my name is  Claudio. I would like to ask a question about an issue that i'm facing while trying to acquire acceleration datas of a vibrating object using an NI 9234. Considering that the acceleration datas refer to a vibrating object I expected to acquire some positive and negative datas with a mean value close to 0. Instead the datas that I'm acquiring are all positive and with a mean value that is pretty far from 0. I tried acquiring those same datas on Matlab, and it gave the expected results. Now what I don't understand is if this is a code issue or something that has to do with the hardware I'm using. I thank you in advance for your answers.

[claudio_gerosa]

I'm sorry. I forgot to specify that to acquire the data I'm simply using the DAQAssistant function. Thanks again.

[GerdW]

Hi Claudio,

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@claudio_gerosa wrote:

Now what I don't understand is if this is a code issue or something that has to do with the hardware I'm using.

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We can't help with this problem as long as you don't attach any code…

[claudio_gerosa]

Hi, thank you for your answer. You're right I should've attached some code. I apologize. I didn't think it was necessary because it is a very simple code that I'm using, basically having only tha DAQ Assistant function, a filter and some graphs. Anyway here's the code that I'm using to acquire data.  I thank you again.

[LVIEWPQ]

You're using Labview 24, if you could save for previous, people will be able to assist better as most people on here don't have access to such modern versions. 

[PsyenceFact]

Hi Claudio,

You can see this sort of effect if the IEPE and coupling settings for the acquisition task do not match the transducer.  Are you using an accelerometer that requires an IEPE constant current power supply?

PsyenceFact

[claudio_gerosa]

Hi, thank you very much for your answer. I am in fact using an accelerometer that requires an IEPE constant current power supply. Are there some settings that I can change to solve the issue? Thanks again.

[claudio_gerosa]

Nevermind, I think I found the setting to change the coupling mode from AC to DC. Again, thank you very much for your help. Have a nice day.

[claudio_gerosa]

Ok, I tried changing the coupling mode but it didn't really solve the issue. I'm sorry.

[PsyenceFact · Accepted solution]

Have you tried using NI MAX to set up your accelerometer channel?  If you can get that to work, you just need to recreate the channel setup in LabVIEW.  For an IEPE accelerometer, you usually have to set the excitation source to be Internal and the excitation value to be either 2.1 or 4 mA (check what your accelerometer requires).

I don't think that DC coupling is correct because the IEPE power supply imposes a DC offset.

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA03q000000x0VRCAY&l=en-GB