Abstract: A magnetic sensor for detecting the leading edge of a ferrous target as it passes the centerline of the sensor. The magnetic sensor includes a coil output representing the rate of change of magnetic flux as the target passes the sensor. The coil output is differentiated to provide a signal having a zero crossover point corresponding to the time at which the leading edge of the target passes the centerline of the sensor. The differentiated signal is applied to a zero crossover threshold detector to provide a first pulse, the trailing edge of which corresponds to the time at which the target's leading edge is coincident with the sensor centerline. Additional means provide a second pulse whose leading edge corresponds to the time at which the leading edge of the target is coincident with the centerline of the sensor.

Abstract: An event rate counter for measuring the number of events occurring per unit of time with an input pulse train having a fixed number of pulses per each occurrence of the event, wherein the input pulse train is scaled by a multiplier and divider to provide a direct readout in events-per-unit of time. The input pulse train is amplified and applied to a level detector, the output of which is a logic level pulse train having frequency equal to the frequency of the input signal. The pulse train frequency is monitored by a frequency detector for controlling a commutative switch. For low frequency pulse trains, the switch gates the pulse train from the level detector first to the multiplier, the output of which is gated by the switch to the divider. The multiply-divide sequence order is reversed by the switch for high frequency pulse trains thereby extending the dynamic frequency range of the counter.

Abstract: An electronic tachograph for providing a chart recording of the speed of a vehicle and the distance travelled by the vehicle in relation to time includes an input transducer coupled to the vehicle drive to provide distance pulses representing the distance travelled by the vehicle, a sampling circuit which samples the distance pulses at a predetermined rate and provides pulses to a speed counter and a distance counter which responsively provide control outputs representative of the speed of the vehicle and the distance travelled by the vehicle for controlling stepping motors which effect the positioning of a speedometer shaft and the incrementing of an odometer, and for moving a speed stylus and an odometer stylus on a recording chart which is driven by a further stepping motor controlled by outputs of a time base generator which supplies timing pulses to the sampling circuit and the speed control circuits.