Need help to measure Distortion on 115vac 400Hz

[Kimlorentz]

I got an PXI-4472 connected to an 115vac 400Hz inverter (voltage is adjusted from 115vrms down to 2.6vrms true resistors) to measure frequency and distortion in percent.

I have no problem reading the 400Hz frequency but when I try to use the Distortion Measurement VI (Signal Processing - WFM Measure - Distortion) I get nothing.

I want to read the distortion in percent.

How do I do that?

The frequency is allways 400Hz +/- 1%.

[Henrik_Volkers]

posting your vi would be of great help to help you 😉

[dsb@NI]

Also, please post a typical dataset with your VI.

[dsb@NI]

I am guessing you found your solution. For the next person with a similar question, please refer to the example VI Harmonic Analyzer Measurement that ships with LabVIEW.

If you want a simple test VI where you control the amount of distortion, you can try the following:

This snippet creates a fundamental tone at 400 Hz and a harmonic at 1200 Hz. When run, this VI returns the expected THD of 1 %.

[Kimlorentz · Accepted solution]

Yes I was able to find my fault. I forgot to multiple by 100 to get the %.