Basic accelerometer-power spectrum readings

[k_savoy]

Hi all,

I'm new to Labview and am trying to create a simple power spectrum logger. I've had a look at multiple tutorials but am stuck getting to places (most of the tutorials require sound and vibration toolkit, are really old and incompatible with Labview 2011 etc). The program I'm trying to do is:

1) Collect signals from accelerometer (4kS/s)

2) Generate power spectrum

3) Save to disk (on board the cRIO)

My setup is:

- cRIO 9014

- NI 9234

- Labview 2011

So far, I've managed to get the signal readings (XYZ axis) and merge them, put them into a 'Collector' block and then output them to the power spectrum block. I've very crudely used a 'Time Delay' block to set the sample rate (which I know is probably not accurate, but I cannot figure out how else to do it). I'm having a problem figuring out how to input the sample rate into the collector, which is why my power spectrum is giving me 0 to 0.5Hz (it's likely assuming the sample rate is 1Hz). I've attached my .vi.

Would someone be able to point me to a tutorial/example/alternative solution? Thank you very much in advance.

[Patricia B]

Hello,

Here's an example that may be of some use:

Power Spectrum Measurement

http://zone.ni.com/devzone/cda/epd/p/id/5803

Power Spectrum Measurements for Simulated Signal

https://decibel.ni.com/content/docs/DOC-2062

Regards,

Patricia

[preston_johnson]

I think what you want is the CompactRIO vibration data logger.  It does not require the S&V measurement suite, though you will find it very useful. 

Check this out!

http://zone.ni.com/devzone/cda/epd/p/id/6388

It has a waveform acquisition template for the FPGA.  It has a data logging state design. 

You can see a Video of it working here

http://www.ni.com/mcm/wind/

Let us know if this helps. 

[k_savoy]

Thanks for the replies.

Patricia: I had a big problem stepping onward from the sine wave generation to actually acquiring the waveform (converting data to waveforms is not as intuitive as I would have liked). But someone from NI has helped me get around that. 

Preston: I had a look at those examples but they require S&V to run. Even though I manually remove the S&V blocks and patch up the connections, there are still very big FIFO errors that I can't seem to resolve. Unfortunately the cRIO examples aren't as out-of-the-box as thought when I purchased the cRIO system.

I've tweaked another example and managed to extract the FFT, but the RT buffer overflows pretty quickly and stops running. Will need to figure out a way around that. Also need to figure out how to write the data to the onboard memory then extract it later on. I will give technical support a call. Thanks guys.