Diagnostic circuit for motor vehicles - provides four simultaneous measurements of ignition system using command signal and evaluating by logic techniques

摘要

Diagnostic circuit allowing simultaneous measurement of several electrical parameters of motor vehicle engines which may or may not have integral monitoring points. The design is aimed at providing a simplified and easily interpreted diagnostic facility, providing four measurements; the peak voltage of the ignition coil secondary into a 1 Kohm load, the supply voltage of the coil, the ratio of open to closed times of the contact breaker and the state of the contact surfaces. The circuitry employs logic AND and gating stages, a comparator with a variable threshold input and a memory circuit.