"robobass" wrote in message
...
I know this is a metalworking site, but there is quite a bit of
expertise on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car
battery on the bench (nothing else attached) and plugged in a few
lamps. The output measured 330v with loads of 50 and 150 watts. The
lights did seem brighter, but not excessively so. The voltmeter is a
cheapie, but seems generally accurate. I know that these devices
produce a modified sinewave, and I should expect a different reading,
but I thought the reading should be lower if anything. Is this
inverter a dud, or do I just not know how to measure?

Thanks

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https://www.automationdirect.com/sta.../sj100/ch6.pdf
"Note 3: A general-purpose digital volt meter (DVM) is not usually
suitable to measure
a distorted waveform (not pure sinusoid)."