Electronic meter for determining engine speed in distributorless

Abstract

An electronic meter for testing engine parameters includes a slide switch and related circuitry for detecting, scaling and displaying the correct value of engine speed for both a conventional four stroke engine and a DIS four stroke engine, as well as for a two stroke engine. The electronic meter has a pickup which is adapted to be placed around a lead from a spark plug in the engine. The electronic meter is adapted to be triggered when a current spike in the spark plug lead is above a selected threshold value. When the electronic meter is triggered, a voltage pulse is stored in an integrating circuit in the meter. The electronic meter scales the voltage across the integrating circuit, measures the scaled voltage, and displays the value on the meter. The slide switch and associated circuitry for the electronic meter are adapted to vary the threshold level for the trigger, as well as appropirately reduce the output voltage of the integrating circuit, depending on the type of engine being tested. When the slide switch is in a first position, the electronic meter displays the correct value of engine speed for a conventional four stroke engine. Alternatively, when the selector switch is in a second position, the meter displays the correct value of engine speed for a DIS four stroke engine or for a two stroke engine.