Abstract: An automatic wheel alignment system for aligning the wheels of an automotive vehicle includes head units adapted for coupling to the wheels of the automotive vehicle and a hand held module. The wheel units provide angle information related to the alignment of the wheels of the automotive vehicle. The hand held module is coupled to the wheel alignment units and provides information to an operator through a liquid crystal display. The hand held module includes a controller and memory means. A keypad input is provided for receiving an input from the operator. The liquid crystal display includes an liquid crystal display matrix for forming an image. A contrast control means is coupled to the liquid crystal display and provides a contrast signal to the liquid crystal display.

Abstract: Automotive vehicle test equipment includes a controller which controls power supplied to a test circuit. The controller monitors a sleep mode switch which determines whether the controller enters a sleep mode. In sleep mode, the controller disconnects the test circuit from a power source. The controller also monitors a telephone line. Upon detection of a ring signal on the telephone line, the controller connects the test circuit to the power supply.

Abstract: An RPM variation test for use in an engine analyzer system is used to test internal combustion engines. The engine analyzer individually disables cylinders and monitors instantaneous engine RPM, to generate an engine map. The engine analyzer performs an engine performance test upon the internal combustion engine. The engine map is used to map the results of the engine performance test. Using the present invention, an engine map is produced just prior to performing an engine performance test.

Abstract: An automated test system makes voltage and resistance measurements. The breakout cable is connected between the vehicle electronic control module and the vehicle sensors and controls. Resistance measurements are made between a selected pair of connector pins of the breakout cable by connecting a current loop (which includes a power supply and a known resistance) through a first multiplexing circuit to the selected pair of pins. A voltage measuring circuit measures voltage across the known resistance and between the pair of pins. The voltage measuring circuit includes a second multiplexing circuit and a voltmeter. The second multiplexing circuit receives inputs from the various pins, as well as from opposite sides of the known resistance in the current loop. The second multiplexing circuit provides its output to the voltmeter for measurement. By measuring the voltage across the known resistance, and the voltage between the selected pair of pins, the resistance between the two pins can be derived.

Abstract: Measurement devices are mounted on left and right steerable wheels of a vehicle. Caster is calculated for each of the wheels based upon measurements made with the measurement devices. Pitch at zero toe is determined for the left and right wheels and a steering axis inclination (SAI) compensation term is determined. Live caster is calculated using the live pitch of the wheel, the caster calculated for the wheel, the pitch at zero toe for the wheel and the SAI compensation term. An output representative of the live caster is provided.

Abstract: An engine analyzer for an internal combustion engine includes an analog-to-digital (A/D) converter which digitizes an analog input waveform representing, for example, a secondary or primary voltage waveform of the ignition coil of the internal combustion engine. The sampling rate of the analog digital converter is determined by dividing the waveform time period by the desired number of samples. An adjustment factor C is used to provide a buffer period during the sampling period of the waveform. A display for displaying the waveform has a buffer region which corresponds to the buffer period. Thus, a variation in the speed of the engine which causes the engine to slow down and extends the period of the engine waveform does not cause a loss of data collected from the waveform because the buffer period provides a margin of error.

Abstract: An anti-tamper device in an automotive vehicle test system monitors an access panel to the automotive vehicle test system. An alarm is actuated if the access panel is opened. The automotive vehicle test system tests automotive vehicles and prints certificates which verify test results. The access panel is unlocked following the completion of an automotive vehicle test so that an operator can gain access to a printer to retrieve a printed certificate. The test system monitors the condition of the access panel even if power is removed from the automotive vehicle test system. A large capacitor provides power to monitoring circuitry. A data latch, powered by the capacitor, latches the condition of the access panel. The alarm is sounded when power is returned to the automotive vehicle test system and the condition of the latch indicates that an access panel has been opened.

Abstract: A wheel alignment system uses head units attached to each of the four wheels of an automotive vehicle. Angle measurements are taken using light sources and light sensors. Pitch sensors measure the pitch of the head units with respect to a horizontal plane. The head units are connected to the left and right front wheels of the automotive vehicle. The pitch information is used to compensate for errors in left and right cross-toe measurements between the left and right front wheels of the automotive vehicle.

Abstract: A cross toe zero calibration system for use in an automotive vehicle wheel alignment system uses a calibration bar for receiving cross toe measuring head units. A first set of cross toe measurements are taken with the bar in a first position and a second set of cross toe measurements are taken with the bar in a second position. In the second position, the bar is rotated 180.degree. from the first position. The two sets of measurements are averaged to yield zone cross toe angle calibration factors. The combination of rotating the bar and averaging the two sets of measurements nulls out errors introduced into the calibration measurements due to deformities in the bar. The calibration bar is mounted on the main console of an automotive vehicle wheel alignment system. Switches are included which indicate the position of the bar.

Abstract: An automotive vehicle wheel alignment system uses a light source and a linear CCD to measure angles. A mask having a slit through which light from the light source is projected onto the surface of the linear CCD is interposed between the light source and the linear CCD. A microprocessor controls the light source and the linear CCD and uses an output from the linear CCD to calculate an angle between the light source and the linear CCD. The microprocessor uses a search algorithm to locate the center of the image projected on the linear CCD. Calibration data for the linear CCD is stored in an EEPROM.

Abstract: A wheel alignment system measures caster and steering axis inclination (SAI) by positioning the wheels at a right turn position and a left turn position. Toe, camber and inclination angle measurements are made for both wheels at both the left turn position and the right turn position. Based upon these measurements, caster and SAI are calculated either directly or through an iterative technique.

Abstract: A signal representing the RPM of an internal combustion engine is produced by a signal processor connected to the battery of the vehicle. The signal processor derives an electrical signal from the battery which contains signal components produced by operation of the vehicle ignition system, as well as components from a multitude of other sources such as the voltage regulator, fans, air conditioning and other electrical systems of the vehicle. The signal processor filters and signal processes the signal derived from the vehicle battery to produce a signal having a frequency which is related to the RPM of the engine.

Abstract: In an engine analyzer system, a test probe adapted for connecting to ignition wires of different diameters. The test probe including a pick-up clip for electrically coupling to the ignition wire and clamping to large diameter ignition wires. A rotatable clip adapted for clamping small size ignition wires is rotatable into alignment with the pick-up clip. The rotatable clip holds small diameter ignition wires in electrical contact with the pick-up clip.

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.