Logarithmic Rate Meters and Period Meters: A Theoretical Study of Noise and Transient Response

Expressions are derived for the output, and time derivative of the output, of the simple diode pump circuit corresponding to an input pulse rate which is increasing exponentially with time. Solutions are obtained in numerical form for a series of values of the diode pump parameters. By a linear superposition of the outputs it is possible to predict the transient behavior of the multiple diode pump type of logarithmic rate meter and of the period signals derived from the output. The fluctuations or “noise” in the period meter output signal for random input pulses is also calculated for this type of rate meter. A comparison based on transient response and noise behavior shows the multiple diode pump circuit to be potentially superior to the simpler logarithmic diode type of rate meter.