Ignition misfiring detection circuit for IC engine

摘要

A circuit for detecting misfiring in an IC engine has an ion current sensor (9a) which establishes a positive voltage at a sparking plug and detects a negatively polarised ion current during the combustion. There is a current/voltage converter (9b) which converts a negative ion current into a positive voltage. The sensor has a condenser (5) charged up by an external source to a positive voltage, a voltage limiting circuit (4) for the condenser and a diode (6) between the condenser and earth. The converter has a second diode (17) and an operational amplifier (18) with low input impedance, whose inverting input is connected between the condenser and the first diode, and whose non-inverting input is earthed.