I need to measure the AC frequency of a 230 V electric generator (gasoline powered). I have a cheap but ok multimeter that does Hz but the reading is erratic (some 1 kHz...) The reading on the mains is a perfect 50 Hz. I also have a TDS-220 Tektronix oscilloscope but I'm scared to blow it. Any idea why I would get that strange reading, or how to safely use my scope?
Edit: I got myself a cheap Wall wart meter and got 60Hz. I suspect that its got only 2 readings, 50 and 60Hz and because of the noise, it switches to the highest. It should read 50Hz. I will try some more tomorrow. One question though: is it normal that there is so much noise on the line?
Edit 2: I managed to get correct readings. I was getting like 53Hz+ but managed to find how to regulate the engine RPM so I can get around 50Hz, but I'm still getting fluctuations of about +-2.5Hz without load, and about -+1Hz under load. Voltage also fluctuates around +-1V at 228V. Do you think this is normal for an entry price generator from a known brand? The wave looks noisy with no load and distorted under load.