Tire pressure sensing system and tire pressure sensing device

摘要

Without providing the oscillating circuit of high accuracy in the pneumatics inspection device which is installed in the tire, the measurement result is transmitted outside with the wireless. The pressure sensor where electric capacity changes according to inflation pressure (42) with the LC resonance circuit is formed with coil Ls. Sensor control unit (10) it detects the fluctuation of the electromagnetic field of the frequency f0 which occurs with coil, L2 it forms the clock pulse on the basis of that, this trance is connected it inputs into the coil Le which to coil, Ls drives the aforementioned LC resonance circuit. The A/D converting circuit (50) with it converts output voltage of the LC resonance circuit which responds to the strength of resonance to the digital data, following to the binary digit string which forms the particular data, it changes the impedance of coil, L2 through the aforementioned electromagnetic field because of this, sensor control unit (10) it generates irregularity to voltage of coil L1.