A TYRE PRESSURE SENSOR AND RELATED ALARM SYSTEM

摘要

A tyre pressure sensor and related alarm system uses a sensor (100) which has a threaded collar (106) and is adapted to be connected to a valve of a tyre. The sensor (100) includes a transducer (12) and a transmitter (9) hermetically sealed in a body. A depressor (104) located on the body, urges against a valve to open it. The body of the sensor (100) may be connected to the threaded collar (106) by way of a shearable collar (120). In use, when first connected to a tyre, the sensor (100) obtains an initial value of the tyre's pressure and stores this initial value. If the pressure of the tyre deviates by more than a predetermined amount from the initial value, for example +/- 15 %, then an alarm signal is transmitted to a receiver which is inside the vehicle. The alarm signal comprises a coded portion and an "id" portion. A (12) bit code is preferably used to ensure sufficient security and this provides approximately 65000 different "id" codes. The invention overcomes problems associated with existing systems, in that the sensor is mounted directly to a valve and it does not require calibrating.