Method and apparatus for measuring air pressure in pneumatic tires

摘要

System for remotely measuring the air pressure in pneumatic tires. The system includes a stationary power transmitter that generates an electromagnetic field in the roadway with a flat coil antenna. Located in the pneumatic tire is a pressure sensor comprising a pressure transducer and a signal transmitter both powered by the energy obtained from the electromagnetic field in the roadway. The pressure sensor does not use a battery and has no external physical connections outside of the tire. The pressure sensor transmits a low frequency FM signal to a stationary tire pressure signal processor. The signal processor generates quantitative signals representing the pressure in the tire, visually displays these signals, and passes the signals to a computer. By means of various antenna configurations the system can distinguish between tires mounted both in side by side and in tandem relationship. Moreover, by coding the FM signal the system can uniquely identify the vehicle as well as every tire thereon. In an additional embodiment the pressure sensor is powered by a current induced from a magnetic field. The sensor in the tire is rotated through a stationary magnetic field generated by permanent magnets attached to the vehicle.