Harmonic Distortion Meter?

[Axtman]

I am in the process of calibrating an old BK Precision function generator. The calibration procedures call for me to use a harmonic distortion meter. Does anyone have any suggestions or is there possibly and online app? Thanks.

[Fungus]

I am in the process of calibrating an old BK Precision function generator. The calibration procedures call for me to use a harmonic distortion meter. Does anyone have any suggestions or is there possibly and online app? Thanks.

A spectrum analyzer will do the same thing. Any distortion in a sine wave will show up as harmonics in the spectrum and you can twiddle to minimize them.

What won't do is produce a nice neat THD number for you.

[bob91343]

It depends on how much distortion you need to measure.  If it's not too low, an oscilloscope may do the job.  If you are working down well under 1% than you need a dedicated meter such as HP 331 that I have.

There aren't too many spectrum analyzers that measure in the audio range, at least for a reasonable price.

[TimFox]

The old rule of thumb was that 5% THD was visible on a CRO.
If you are looking for a used -hp THD meter, I recommend the 333A, 334A, or 339A, which all have auto-null capability (after gross tuning).  The 331A and 332A require manual nulling, but otherwise work well.  The 332A and 334A also have an AM detector, which is only needed for broadcasters.  My 339A is better than the spec of 0.002% THD (instrument-induced distortion).   An advantage of the 339 is that it will normalize to the input level should it change during your adjustments. 

[JDubU]

If it's for the audio range, you might be able to use a computer sound card with a spectrum analyzer app. 
For example: https://trueaudio.com/rta_abt1.htm

For others, do a Google search for:  sound card audio spectrum distortion analyzer

Edit:
Here's a free one:  https://www.roomeqwizard.com/features.html

[Axtman]

The calibration procedures say 0.7% distortion on sine wave. See attached file.

I'm considering "faking" it by putting a sine wave (from a reliable source) in one channel and the BK Precision sine wave in the other. Then I would overlap the two waves and try to match them up.

[DaJMasta]

If you've got a DSO with an enhanced resolution mode, you can probably at least spot check that with its FFT feature.  Otherwise a spectrum analyzer has the high bandwidth, and audio analyzers (sound cards would be fine) or power meters in the lower frequency range should both work well.