Revolution speed detecting apparatus

摘要

Through differentiation of input signal Vw from a sensor the angular frequency omega becomes included in the amplitude component. Through a plurality of differential operations the amplitude including the angular frequency omega varies, but the time-dependent term becomes equal. Since the amplitude of the signal Vw outputted from the revolution speed sensor 10 is approximately constant, the angular frequency omega proportional to the revolution speed can be extracted by determining a ratio thereof. <IMAGE>