| 摘要 |
A pressure monitoring system has a first chamber (11) and a second chamber (12) separated by a diaphragm. The diaphragm carries respective SAW devices on the respective sides thereof, the SAW devices having different resonant frequencies. Variations in pressure within the second chamber (12) relative to the pressure within the first chamber (11) will cause deflection of the diaphragm and the resulting changes in resonant frequency of the SAW devices can be analyzed to indicate the pressure differential between the chambers. The pressure-measuring device is incorporated within a valve assembly for a vehicle tire. When the vehicle tire is inflated, the inflation pressure is trapped within the first chamber (11) as a reference. Any subsequent loss of pressure from the second chamber (12), e.g. as a result of a puncture, will cause deflection of the diaphragm and a corresponding output from the SAW devices.
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