true rms value

most ac currents and voltages are expressed in effective values, also known as rms (root mean square) values. the rms value is the square root of the squared mean of the alternating current or voltage values.
many clamp meters with rectifier-type circuits have scales calibrated in rms for ac measurements. however, they actually measure the average of the input voltage or current, assuming the voltage or current is a sine wave.
the conversion factor for a sine wave, which is obtained by dividing the effective value by the average value, is 1.1. these instruments can cause errors if the input voltage or current has a shape other than a sine wave.

CF : Crest Factor = Peak value/RMS value
DC = 1
Sine wave = 1.414