The operating principle is directly measure the temperature of the connecting rod big end bearing using a temperature sensor fitted as close as possible (within a few a millimetres) to the bearing surface. The sensor then keeps in touch with the outside world by using a patented, surface acoustic wave (SAW) radar technology, which has been to be the most reliable technology for real-time wireless temperature monitoring. The signal processing unit (SPU) generates a radio wave pulse, which is picked up by the stationary antenna and converted into an acoustic wave which is sent to the rotating sensor. This acoustic wave propagates along the surface of a SAW chip fitted with multiple reflectors, thus permitting the sensor to reflect back a pulse train to the stationary antenna; the time delay between echoes depends on the temperature of the SAW chip