Abstract: A wheel alignment system uses head units attached to each of the four wheels. The front head units contain photodetector arrays which view across the front of the vehicle and to the rear. The rear units carry photodetector arrays which look forward. Each photodetector array views a target on one of the other head units. A microcomputer in each head unit determines an angular value based upon the position of the target image on the photodetector array. The angle values determined by the microcomputers of the individual head units are supplied to a master computer in a main console which determines individual toe angles with respect to a tread centerline for either the front two wheels or for all four wheels. The master computer controls a display at the main console, as well as a remote display to guide the mechanic in making alignment adjustments.

Abstract: An engine analyzer tests operation of a multicylinder internal combustion engine by disabling selected cylinders. The apparatus includes a semiconductor switch connected in parallel with the ignition points (or solid state circuit interrupter) of the engine's ignition system. A cylinder clock signal is derived from the engine, and exhibits a first signal transition each time the points open. A cylinder counter maintains a cylinder count identifying the current cylinder, and a period measurement timer measures the time period for each cylinder based upon the time between each first signal transition of the cylinder clock signal. The previously measured time periods of the cylinders are stored in a table which is constantly updated. Each time a first signal transition occurs, a programmable time delay timer is loaded with an input value which is based upon a previously measured time period for the current cylinder.

Abstract: An ignition analyzer apparatus tests the condition of the ignition coil of an internal combustion engine. A gating pulse is supplied to a test circuit immediately before the points are to open for a selected cylinder which causes the test circuit to provide a low resistance in parallel with the points when the points open. This allows a reduced primary current to flow through the ignition coil and prevents the production of a voltage pulse large enough to fire the spark plug for the selected cylinder. While the points are open and the test circuit is providing a low resistance path, the primary current flowing through the coil is measured. The gating pulse ends approximately half-way between the "points open" time of the selected cylinder and the "points open" time of the next cylinder so that the rotor of the distributor is between distributor terminals.

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 memory. 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.

Abstract: Engine timing apparatus includes a timing light, cylinder clock signal circuitry, a cylinder counter, a cylinder comparator, first, second and third timers, a trigger pulse generator, operator control buttons, and a computer. The first timer measures a first time period between firing of the No. 1 cylinder, and the second timer measures a second time period between firing of the cylinder preceding No. 1 and the firing of the No. 1 cylinder. The computer derives from the first and second time periods a first digital value which represents the angular degrees from firing of the cylinder preceding No. 1 to firing of the No. 1 cylinder. Each time the comparator output signal is produced, the third timer initiates an adjustable time period, and the trigger pulse generator triggers the timing light at the end of the adjustable time period. The operator control buttons include buttons which cause a second digital value to be increased or decreased.

Abstract: An engine analyzer for an internal combustion engine includes circuitry, under the control of a microprocessor, which senses parameters of operation of the internal combustion engine and supplies digital signals indicative of those sensed parameters. A raster scan cathode ray tube (CRT) display is controlled by the microprocessor to display a simulation of an analog meter having a pointer or needle which moves as a function of the digital signals. When an analog display, such as a tachometer, is selected, the microprocessor controls the raster scan CRT to display a visual depiction of a meter having the appropriate range of values and having a needle which moves according to the measurements made by the system. The microprocessor automatically changes the scale of the simulated meter as appropriate without operator intervention.

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: 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.