Telemetry unit

摘要

A telemetry unit ( 100 ) is provided for mounting to the inside of a pneumatic tyre, which includes sensors for measuring the pressure and temperature within the tyre and an RF transmitter for transmitting measured data to an on-board display remote location. The unit ( 100 ) includes a piezoelectric element ( 114 ) supported in a housing ( 112 ) with an actuator ( 136 ) arranged for contact with the element ( 114 ), to deflect the element ( 114 ) in response to external forces acting on the actuator ( 136 ) during rotation of the tyre. For every rotation of the tyre, cyclic pulses of electrical charge are generated by the deflection of the element ( 114 ). The unit ( 100 ) includes control means which controls the consumption of stored charge when measuring and transmitting data and is arranged to vary the rate of transmission of data from the unit ( 100 ) in dependance on the rotary speed of the tyre.