read the average value of the voltage. Some meters measure RMS but only for a sine wave. Older true-RMS meters used thermal or electrodynamic methods to measure the RMS value. However, modern ...

Then there was root-mean-square (RMS) voltage. For those nice sine waves, you took the peak voltage and divided by the square root of two, 1.414 or so. You know that kid in the front of the class?