When the waveform (e.g. sinusoidal, triangular, square) of the input signal is known, its crest factor, defined as the quotient (Q_{CF}) of the peak (V_{p}) and RMS (V_{rms}) values, can be used to set the constant K in the mathematical function K*X+L. The display will then show the actual Vrms value of the input signal, assuming that V_{pp} is the main parameter.

Example: A sine wave has a crest factor of 1.414 (√2), so the constant in the formula above will be 0.354.