What is PPM(Peak Program Meter)?
PPM (Peak Program Meter) is designed to measure the peak value of a signal. Developed initially in 1932, the PPM meter as we know it today appeared in 1938. However, PPM does not indicate the actual peak voltage of the signal. The early devices used a 10ms detection time (Type II meter), and later this was reduced to 4ms (Type I meter). These detection times were chosen to ignore the quickest transient peaks, resulting in PPM often being called “Quasi PPM,” distinguishing it from true PPM. Very short transient signals can be displayed about 4dB lower. The reason for ignoring transient peaks is the assumption that momentary overloads in recording or transmission equipment are generally inaudible if they are less than 1ms analog overloads.