Abstract: A vehicle diagnostic system suitable for coupling to a CAN bus. The system has a connector which is coupled directly to the CAN bus and an analyzer which is coupled to the connector by relatively long cables. A buffer is located in the connector to isolate the electrical load represented by the cable from the CAN bus and to communicate signals transmitted from the analyzer to the bus and received from the bus to the analyzer. Thus data can be read directly from the bus to conveniently located analysis equipment.

Abstract: An apparatus and method for testing, for example, ABS systems in which a variable reluctance detector is positioned adjacent a ring of ferromagnetic teeth mounted on a wheel is provided. The amplitude and period of individual cycles of the output of the detector are measured and the product of the measured amplitude and period is calculated to provide an indication of the performance of the ABS detector system. The rate of change of the product may be analyzed to more reliably distinguish fault conditions from the effects resulting from, for example, variations in the speed of the wheel. The peak-to-peak amplitude of the product may be monitored to indicate tooth eccentricity, and the mean of the product may be monitored to indicate the detector-to-tooth gap.

Abstract: A system for identifying faults in an electrical circuit such as a circuit of a road vehicle. The electrical circuit is intended to provide a plurality of outputs such as lamp illumination in response to predetermined circuit conditions. Data describing individual components of the electrical circuit and the interconnections therebetween is stored. Data identifying a fault symptom is input to the system by a technician to indicate that for one said predetermined set of circuit conditions the intended output is not provided. Stored data is accessed which describes selected components which if faulty could be the cause of the fault symptom. Values of electrical variables to be expected at predetermined measurement points in a sub-circuit defined by the selected components and the connections therebetween are calculated.

Abstract: Propagation delays in signal paths leading to respective pins in an array of test system pins are determined using a probe which is wiped across the pins. Timing signals are applied to each of the signal paths in parallel, and pin identifying signals are applied to each of the signal paths such that each signal path and the pin to which it is connected receives a different pin identifying signal. When the probe is wiped across the pins, it detects signals on each of the pins with which it comes into contact. Any pin with which the probe is in contact is identified by detection of the pin identifying signal. The identifying and timing signals alternate, and once a pin has been identified, the timing signals on that pin are detected. The propagation delay in the signal path to the identified pin is then calculated from the detected timing signals.

Abstract: A method and apparatus for sequentially refreshing each of an array of sample and hold output circuits in a DC level generator. Each sample and hold circuit makes a selected DC voltage available. For each of the sample and hold output circuits in turn, the voltage which it is desired to store in that circuit is generated. The generated voltage is compared with the voltage stored by that one sample and hold output circuit to produce a voltage difference signal and an error correction storage and hold circuit is charged to a voltage proportional to the voltage difference signal. Charge proportional to the voltage stored in the error correction storage and hold circuit is then transferred to the selected one sample and hold output circuit to reduce the difference between the compared voltages.