Abstract: An engine analyzer performs electrical tests on a multi-cylinder internal combustion engine under the control of the digital computer. The engine analyzer includes a hardware cylinder counter which keeps track of the current cylinder number while various engine tests are performed. The hardware cylinder counter is a programmable digital counter under the control of the computer which performs the cylinder count function independent of operation of the computer. The counter has jam inputs for receiving an input count from the computer which represents the number of cylinders of the engine under test. The counter is counted down in response to a cylinder clock signal. The counter is reset to the digital value at its jam inputs whenever its Set input is pulsed. A synchronizing circuit is responsive to a No. 1 cylinder pulse and to a carry-out pulse which is produced by the counter when the count reaches zero. The counter is reset to the input count whenever the No. 1 pulse or the carry-out pulse is present.

Abstract: The condition of a storage battery of an internal combustion engine powered vehicle is tested automatically, and an indication of battery condition is provided to the service technician. The battery testing apparatus is connected to the positive (+) and negative (-) terminals of the battery to measure battery voltage under several different conditions. In particular, the battery testing apparatus measures battery voltage under open circuit conditions, while subjecting the battery to a predetermined AC load, and while subjecting the battery to a predetermined DC load. The battery testing apparatus also includes a temperature probe which measures the temperature of the battery.

Abstract: An engine analyzer for an internal combustion engine includes an analog-to-digital (A/D) converter which digitizes an analog electrical input waveform representing, for example, a secondary or primary voltage waveform of the ignition coil of the internal combustion engine. The digitized input waveform is stored in the form of digital data in a data mamory. Upon request by the operator of the apparatus, a microprocessor selects digital data stored, and supplies that digital data to a display, which displays a visual representation of the waveform based upon the selected digital data. The engine analyzer apparatus produces a constant width waveform regardless of engine RPM, by determining the period of the waveform to be stored, and then varying the sample rate at which the A/D converter samples the analog waveform and converts the sampled waveform to digital data. As a result, the number of data samples, and thus the width of the displayed waveform, is constant.