Abstract: A tire pressure sensing system for on-board use in an automotive vehicle comprises a transmitter mounted to rotate with each tire and a receiver that is disposed in sensing relationship to each transmitter. Each receiver is a Hall Effect sensor. Each transmitter comprises three magnetic poles that are effective to cause the Hall Effect sensor to develop a bi-directional pulse waveform during passage of the transmitter past the receiver. Electronic circuitry processes the signal waveform that is created by the Hall Effect sensor in response to passage of the magnetic poles. The circuitry develops one rectangular pulse waveform from one magnetic polarity and another rectangular pulse waveform from the other magnetic polarity.
Abstract: An on-board tire pressure indicating system comprises for each tire of a vehicle, a receiver disposed adjacent the rotating wheel on which the tire is mounted. On the wheel is a transmitter which comprises three magnets, spaced apart in a general circumferential sense, and lying on essentially the same radius. As the wheel rotates, the magnets repeatedly sweep past the receiver, which generates a pulse at the passage of each magnet. Two of the three magnets are disposed in a predetermined fixed circumferential spacing on the wheel. The third magnet is selectively positioned in a circumferential sense relative to the other two magnets in accordance with the pressure in the tire. The time between the two fixed magnet pulses corresponds to a reference measurement dimension while the time between the selectively positioned magnet's pulse and the one of the two fixed magnet's pulse corresponds to an inflation pressure measurement dimension.