Digital tachometer for IC engine - has integrated clock source and adjustable time base to count engine firing pulses over three second cycle to obtain direct read=out of revs

摘要

The tachometer, for a road vehicle or boat engine, counts the engine firing pulses over a period of 3 seconds to allow the result to be displayed directly in terms of revs/minute. the tachometer has fire stages comprising an input, a precision clock source, a stabilised voltage supply, a counting memorising and decoding circuit and a display module. Pref. an integrated clock source is used with a rotary potentiometer used to adjust the precision and the period of the clock pulse signal. The time base can also be adjusted by varying a resistor or capacitor within the clock source circuit.