Arrangement for measuring the conduction angle of an ignition coil in a

Abstract

An instrument of the type employed to measure the conduction angle of the ignition coil of the battery-powered ignition system of an internal combustion engine comprises input connectors which are connected to terminals of such ignition system and an evaluating circuit which generates a signal corresponding to the conduction angle to be measured by ascertaining whether an input signal derived from the input connectors rises above or falls below a predetermined threshold voltage level. For differing types of conventional ignition systems, differing threshold voltage levels are required, but instead of resorting to manual switchover to such different levels, the instrument of the invention modifies the threshold voltage level employed in automatic dependence upon the value of the input signal derived by the input connectors. The threshold voltage level assumes a first value when coil conduction ceases and a second value when coil conduction recommences. A signal-storing circuit generates signals indicating whether or not the input voltage reaches or fails to reach a predetermined value, the predetermined value being indicative of what type of ignition system is involved, and then persistently stores such signal, the stored signal serving to automatically change at least one of the aforementioned first and second values.