I did not know you could see that with a meter, I thought you'd have to use an oscilloscope.Check HZ the same way you test for voltage, only on the HZ setting.
Most people do Phase to ground.
Poor man's alternative. Someone correct me if this is wrong. Measure the neutral current with an average-responding meter (that is, just a regular less expensive non-true-RMS meter) then measure again with a TrueRMS meter. If the current is different, it's likely due to presence of harmonics. (Of course you still would not know the frequency of the harmonics.)No, I would of never thought of that. How the heck to you check hertz?