Abstract: A method and a circuit are provided for detecting low level ionic currents. An ionization detection voltage is applied to a spark plug and a resulting output voltage signal is sent to a threshold device. The output voltage signal is developed by a low offset operational amplifier. First and second serially connected Zener diodes carry current in a normal diode direction when a spark event occurs and carry current in their Zener breakdown mode upon recovery from the spark event. A second operational amplifier and its associated feedback circuit generate a guard voltage which is applied to the junction of the two Zener diodes. The guard voltage is regulated to track the input voltage to the circuit at the cathode of the first diode. Because the guard voltage is essentially the same as the input voltage, there is no leakage current flow through the first diode.

Abstract: Provided is a method and circuit for detecting cylinder misfire in an internal combustion engine having an ignition system including an ignition device, an ignition coil having a primary and a secondary winding, and a pair of spark plugs having respective gaps. As disclosed, the circuit is operative to separate spark current and ionization current to improve detection of cylinder misfire. The circuit includes power supply means for supplying voltage to the circuit to generate ion current across the spark plug gaps and voltage limiting means for isolating said power supply means from said ignition coil. There is also included negative voltage clamping means in electrical contact with the ignition coil secondary winding for clamping selected negative voltages generated during ignition.

Abstract: This invention provides an self-calibrating buffer amplifier for a Universal Exhaust Gas Oxygen sensor interface circuit which couples and processes a voltage signal proportional to pumping cell current to a level and reference voltage suitable for input to an A-to-D convertor. The goal of this invention is to increase the accuracy of air-to-fuel ratio control by continually correcting for the effects of offset quantities in the amplifier stage necessary to the interface circuitry. This goal is accomplished by an approach which effectively generates and subtracts these offset quantities from the processed signal.

Abstract: An ignition system for an internal combustion engine having a flywheel coupled to a plurality of bipolar magnets and a camshaft coupled to a unipolar magnet. A bipolar Hall sensor is positioned adjacent the flywheel for detecting passage of the bipolar magnets and generating a square wave signal to provide camshaft position. A unipolar Hall sensor is positioned adjacent the camshaft for detecting the passage of the unipolar magnet and generating a square wave signal to provide a reference signal indicating a known position of one cylinder.

Abstract: A system for accurately digitizing a signal from a high density optical tachometer using a psuedo zero-crossing detector for subsequent use in a speed measuring device. An added enhancement of the system is the ability to double the frequency response of the input signal to thereby provide a more sensitive indication of incremental speed changes.