FAQ: Can the IntegraVision power analyzer measure interharmonics?

Yes, IntegraVision can measure interharmonics, but not from the harmonic table view, which only shows multiples of the fundamental frequency.

The harmonic table view takes all frequencies (including interharmonics) and places them in the appropriate harmonic “bucket”. So for example, if the signal fundamental is 60 Hz, then there is a 60 Hz bucket, a 120 Hz bucket, etc and these are listed in the “harmonic frequency” column. Frequencies between 60 Hz and 120 Hz are examples of interharmonics. A signal at 65 Hz, for example, would get included in the 60 Hz harmonic bucket. 108 Hz, for example, would get included in the 120 Hz bucket. In this way, all frequencies are accounted for in the harmonics table, but you can’t see the individual interharmonic frequencies in the harmonic table because they are grouped together.

Here is an example for what you might see for a fundamental of 1 kHz:

Now, if you wanted to see the 1.5 kHz interharmonic you would want to look at the magnitude of the spectrum at that frequency by placing a cursor there (intersection of X2 and Y2 below):

Above is the Math FFT with a cursor at 1.5 kHz, showing 10 dBv magnitude. So, it is possible, but keep in mind that this is an approximation from the data shown on the screen and does not use the CWA (Continuous Whole-cycle Analysis) measurement, so the data is not gapless (as you may notice from the “bins” on the purple trace). (The CWA measurement is done on the DFT for harmonics, not on the FFT, which is a Math function. The only measurements that are made using CWA are the ones you see when you press the Analyze button on the front panel. Other measurements – e.g. from pressing Math or Cursors, etc. – do not use CWA.)

 

Applies to: PA2201A

Select Home to return to the table of contents for more FAQs.

Visit our Power Products Forum for additional topics and discussions.

Read technical postings on our Power Blog – Watt’s Up?