Why does my power inverter only measure approximately 200V when using a standard multimeter?
True RMS Fluke multimeter will need to be used to accurately measure the volts of a Modified Sine Wave inverter. The rated voltage is an RMS (root mean square–they square the value to make sure it is always positive, then average it, then take the square root of the average to make up for having squared it in the first place) measurement. Most multimeters are designed to give correct RMS readings when applied to true sine waves, but not when they are applied to other waveforms such as a Modified sine wave. When using a standard multimeter to measure the rated voltage from a modified sine wave inverter, your readings could be 5% to 20% lower in the true voltage.
