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DAQ accelerometer: high sample rate and high number of samples

Hi everyone,

 

I have a self-designed burnishing tool, to which a piezoelectric module is attached. That module is excited by an external source, being the theoretical resonance frequency 40 kHz. I would like to instrumentalize the tool to see if, in effect, that is the working frequency, and to assess how it changes when the tool is working makes contact with a certain material.

 

From now on, I warn you, you nay notice that I am a mechanical engineer (I might say something stupid).

 

For that instrumentalization I have chosen a NI 9223 module, connected to my PC through a cDAQ 9171. A 352C03 accelerometer from Piezoelectronics is the selected sensor (technical satasheet attached). Hardware seems to work fine.

 

Now, I made a very simple programme to visualize data as I acquire it, and save it to a file. I record directly the voltage readings of the accelerometer, as all I want to know afterwards is the frequency of the signal (amplitude is not important).

 

I choose a sampling frequency of 80000Hz (two times 40kHz, according to Nyquist), and 500000 samples. Why that number of samples? Because for greater numbers I have a problem with the buffer and data acquisition, and get an error. BUT I am not happy with this number of samples, because that allows me to acquire data for just 6.25 seconds. I would like to monitor the first 10 seconds, at least.

 

So, my great doubt is how can I increase the number of samples to succeed in monitoring the first at least 12 seconds of the experiment? 

 

Then comes the great doubt, whether I am right in this strategy, or whether there is something missing in my reasoning. Of course I welcome general improvements in the program itself.

 

I attach the technical datasheet of the accelerometer, and the program I did as well. 

 

Thank you all!!

 

Ramón

 

 

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Thanks for the post Ramon,

 

I think you are off to a good start.  The express VIs can get you prettry far.    A couple of notes:

 

1) themaximum sampling rate of the 9233 is 50kHz, so your maximum bandwidth (using 2.56 instead of 2) is 20kHz or so.  20kHz is the maximum you will be able to see in the spectrum with the 9233. 

 

2) I see in your DAQmx express VI, you have it set up for N samples.  You need to set it up for continious.  I would set the number of samples in each read to be 10,000 or more, so you can see a good waveform and see updates prettry frequently.  You will want to also try 50,000 samples as well (once per second updates).     

 

3) because the way the continious block reads, I would simply start a new VI, drop down the express block, configure it as continious, and then add the rest of the items as you did originally.  the express block will create the loop for you. 

 

4) once you get the continious acquisition loop running, you will want to speed up and slow down your machine.  When you do this you will excite resonances in the machine that will show up as increased vibration. 

 

Hope this helps. 

 

Preston

Preston Johnson
Solutions Manager, Industrial IoT: Condition Monitoring and Predictive Analytics
cbt
512 431 2371
preston.johnson@cbtechinc
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Hi Preston. First of all, thank you for your fast and accurate answer.
There is, anyway, a misunderstanding, as the module I am using is the 9223, not the 9233 as you stated. 9223 can sample up to 1MHz, I think. Does this change the answer anyhow?
Thank you so much once again. I'll try to improve the program as soon as I return to my office.
Ramón
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Thanks for the clarrification.  No, the answer does not change.  Just make sure your accelerometer has the ICP power it needs. 

 

Preston

Preston Johnson
Solutions Manager, Industrial IoT: Condition Monitoring and Predictive Analytics
cbt
512 431 2371
preston.johnson@cbtechinc
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Hi Preston,

 

I had dropped your name last week when a copule of high flying NI were presnting to my costomer when one of them replied under hsi breath "Preston is no longer with us".

 

While NI may have lost a giant, the community aperantly has NOT!

 

Take care,

 

Ben

Retired Senior Automation Systems Architect with Data Science Automation LabVIEW Champion Knight of NI and Prepper LinkedIn Profile YouTube Channel
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Wow!! I can't wait to follow Preston's advice. 🙂
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