Need advice on best way to acquire multiple vibration waveforms from a PXI-4472 board

[chc5e]

I'm using a PXI-4472 board to acquire vibration data from 8 proximity probes, each with different scaling. Confused as to best approach to achieve this given all the options with MAX, LabView and its Sound & Vibration toolset scaling. Reading other posts, it appears that 24 bit acquisition also requires some special treatment.

This acquisition needs to be done continuously.
As an additional side note, I will eventually need to synchronize these channels with the channels on 2 other 4472 boards.
Any advice on how to use MAX in combination with LabView's AI CONFIG, START, READ, CLEAR and scaling
for this application would be greatly appreciated.
All the best,
Hunter

[preston_johnson]

Hunter,

Try the following VIs, it synchronizes all the 4472s in your chassis. For prox probes, you will want to use AC coupling if your gap voltage is near or outside the range of the 4472 (-10V). DC coupling will work if your gap voltage is say -7V.

Let me know if you have questions regarding the VIs

Sincerely,

Preston Johnson
National Instruments
preston.johnson@ni.com

[Ben]

Hi Preston,

Could you please register as an enthusiast so we can subscribe to your posts?

Thank you,

Ben

[chc5e]

Thanks, Preston!!! I'll have an attentuator ahead of the 4472's so that I can use DC coupling for shaft centerline considerations.
I have several followup questions regarding the VI you sent:
1. Can I use this as a subVI?
2. What is the purpose of the sequence structure?
3. Should all scaling of the waveforms occur within the main WHILE loop?
4. If so, then I shouldn't create any virtual DAQ channels within MAX, correct?
Sure appreciate the help,
Hunter

[chc5e]

Thanks, Preston!!! I'll have an attentuator ahead of the 4472's so that I can use DC coupling for shaft centerline considerations.
I have several followup questions regarding the VI you sent:
1. Can I use this as a subVI?
2. What is the purpose of the sequence structure?
3. Should all scaling of the waveforms occur within the main WHILE loop?
4. If so, then I shouldn't create any virtual DAQ channels within MAX, correct?
Sure appreciate the help,
Hunter

[preston_johnson]

Thanks for the additional questions.

1) yes, you can use the config, start, read, clear blocks in the example the same as you use the traditional DAQ VIs

2) the sequence structure resets all boards and internally cycles through reading data from all boards

3) yes - scale the data with the S&V or OAT scaling functions after the read block in a while loop

4) Max Virtual channels are of little value in this one. In the future, this example can be updated to take of Max, when Max catches up with DSA.

Thanks for the reply.

Preston Johnson

[preston_johnson]

Done, I think. Let me know if it is working.

[Bryan F]

Hello Hunter --

In regards to your questions...

For scaling, I would recommend using either MAX or the Sound and Vibration Toolset (SVT) scaling, but not both together. The SVT is a bit more flexible, and in general I prefer that. One other thing to keep in mind about MAX is that virtual channels for accelerometers and microphones provide an option to control IEPE excitation, but in fact this can only be set from LabVIEW for the 4472.

24 bit acquisition does not require any special treatment if you are only reading the scaled (i.e. voltage or engineering unit) data. If you use the binary array option for AI read, you will only receive the top 16 bits.

If you use the SVT scaling, you should not worry about MAX at all. If you you do define virt
ual channels in MAX for scaling, you should simply wire a channel array with those channel names into AI Config. Other than this, what you do in MAX should not change how you write the LabVIEW code.

Please see the attached example for synchronizing PXI-4472s.

Hope this helps!
Bryan