Comparing input waveform to known waveform

[Prideaux]

Hello, I am developing an automated tester for our product line and have stumped myself.  On our current test setup the operators compare the shape of the waveform to the known printout from a golden unit, but I can't seem to figure this out in Labview.  The waveform I am looking at is near sine wave around 20khz, and about 20-25 mV rms.  I am checking the frequency and RMS amplitude to ensure quality, but want the automated tester to compare waveform shape to ensure that it is correct.  I realize that an improper shape will most likely fail my overall test for other sub-tests I am running, but wouldn't mind having this checked as well.

My setup is a PXI system with a 6220 daq card (among others), everything is working great, but don't know if there is an easy way to do this.

Thanks for the help!

Shane

[Dennis_Knutson]

What I use is the limit testing functions (Analyze>Waveform Monitoring palette). There's a shipping called Limit Testing Measurement and another one called Limit Testing that uses the Mask and Limit Testing express VI.

[tbob]

You can also use the SINAD Measurement vi.  This will give signal to noise measurement and total harmonic distortion measurement.  If the waveform being tested is deformed, or not close enough to a true sine wave, you will get a lower SINAD measurement and/or a higher THD measurement.  This vi will also give the fundamental frequency.  See attached example.  Put in various values for the noise amplitude and see the changes in SINAD and THD.

[Prideaux]

Wow that was fast, thanks for the quick response. Definetly pointed me in the right direction, now to play with it and see which way works better for my app.

THANKS !