Distortion spectrum

Is it possible/easy to make a graph/plot like the one attached?

It’s not important for it to be a bar graph. A spectrum is fine, but scaling the fundamental to 0dB and automatically identifying the harmonics and their relative levels is what I’m hoping for.

Hi @Aaholm, the easiest way to see the relative levels of harmonics is to put a marker on the fundamental and the harmonics you are interested in seeing.

This will give you a table that shows the frequency, absolute and relative levels to the fundamental. The fundamental is indicated by the green F on the bottom of the display. You can select the fundamental detection strategy by control+clicking on the THD or THDN button. There you will see the option for the fundamental as being either the SigGen1 settings, the highest peak, or a user frequency.

When reading values from the table, note that the table is sorted. So, you’ll see M2 (3 kHz) is shown at -99.5 dBC while M1 (2 kHz) is at -100.75.

To add a marker, just click on a peak. To delete all the markers, right click and pick “Delete all markers” or hit ‘D’.

If you had to have a bargraph, you could export the raw data and use excel macros to pick a max in a range.

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What I was hoping for was an easy way to shift the y axis so that 0dB would be the level of the fundamental (not locked to 0dBV) and then all the harmonics were assigned a marker automatically. I know all the information is in the plot and that the markers work fine, but it’s a little tedious. Can it be automated in the software, or is the only option to export the data and use other tools for that.

You can do that too: Just control+click on dbr button and then click “Set Display Peak to 0 dB” and you get the following. Note the peak is now 0 dBr.

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Thanks! I wasn’t aware of that option. Very nice. That’s close enough to what I was looking/hoping for.

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