Engine speed measuring device with plural counters for averaging angular velocity

Claim 1

A frequency indicator adapted to receive revolution sensor output pulse signals indicative of the angular velocity a revolving object and to use the signals to indicate the frequency of revolution of the revolving object, said frequency indicator comprising a) a time based frequency oscillator effective to generate a sequence of time based signals; b) first counter circuit means coupled to said time based frequency oscillator and to said revolution sensor output pulse signals, for receiving a first one of said revolution sensor output pulse signals, and thereafter for receiving and counting a number of said sequence of time based signals, and for receiving a second one of said revolution sensor output pulse signals, and thereafter for outputting a signal indicative of the received number of said sequence of signals occurring between every pair of said first and said second sensor output pulse signals; c) pulse number counter means coupled to said revolution sensor output signals for receiving said revolution sensor output pulse signals and for outputting a signal indicative of the sum of said revolution sensor output pulse signals received by said pulse number counter means; d) second counter circuit means coupled to said time based frequency oscillator for receiving said sequence of time based signals and for outputting a trigger signal after receiving a predetermined number of said sequence of time based signals and; e) revolution means coupled to said first counter means, to said pulse number counter means, and to said second counter circuit means, for receiving said trigger signals and in response to said trigger signal determining said frequency of revolution of said revolving object by mathematically combining said output signal from said pulse number means with said output signal from said first counter means, and for outputting and displaying a signal indicative of said determined frequency of revolution.