Measuring wow and flutter of a phonographic turntable with digital equipment

Wow and flutter is a phenomenon of frequency modulation. Human ear is sensitive to instantaneous frequency deviation in the range of 0.1Hz ~ 200Hz. The frequency deviation from the carrier frequency can be shown on a FFT analyzer, provided that the FFT frequency resolution, which is equal to SamplingRate/FFTSize, is enough. Quantitative measurement of wow and flutter requires FM demodulation (see https://www.researchgate.net/publication/344437920_Wow_and_Flutter_Measurement_using_Multi-Instrument)

A frequency meter measures the average frequency not the instantaneous one and thus is not able to reveal the wow and flutter. It can only measure the frequency drift.

If the platter has strobe markings on it, maybe there’s a different way: use an optical sensor to pick up the pattern and feed that to your analysis system. Or, you could even make a disc with that pattern and apply that to the platter. Just a thought.

Bonus: a video from AnalogMagik describing their system, showing both optical and reference disc methods. https://www.youtube.com/watch?v=DdbtXseqU2I

Digital oscilloscopes likely employ crystal oscillators for their time-base frequency source. My rather ordinary DSO spec's the horizontal time-measuring scale ±50ppm over any ≥1ms time interval. Good enough to do the turntable speed calibration for your ear. 100 part-per-million accuracy spec (or better) on the horizontal scale likely means that a crystal is used as the timing source.

A careful setup of triggering may be required. You should be able to see wow by adding trigger holdoff. Or simply slide the horizontal position to view the 3kHz signal some considerable time after the trigger point.

If you have an old-school oscilloscope with less-accurate time base that's not based on a crystal but you have an accurate source of 3 kHz signal (or some multiple or sub-multiple of 3 kHz), you can use the oscilloscope's XY mode to compare your accurate source against the turntable output signal, using Lissajous figures. Very accurate, perhaps too accurate to see large variations of speed or wow or flutter.