METHOD OF MONITORING PRESSURE IN A PNEUMATIC TIRE

摘要

A method for monitoring pressure with a transponder (200, 604) capable of measuring temperature data (NT) and pressure data (NP) in an object (e.g., a tire, (104)) and transmitting a data stream (Figure 3C) to an external reader/interrogator (106, 400). The transponder includes a memory (238) for storing measurements, calibration data (662), transponder ID number and the like. Since the transponder combines temperature and pressure information in the "pressure" data, the ratio NT/NP is a direct indicator of pressure-only, and is also relatively insensitive to transponder power variations. The calibration method employs a calibration chamber (602) containing reference pressure (614) and temperature (612) sensors. The transducer to be calibrated is placed in the chamber and exposed (652) to a number of predetermined temperatures and pressures (as measured by the reference sensors) at a number of calibration points. At each calibration point, a temperature reading (NT) and a pressure reading (NP) sensed by the transponder are recorded along with the reference temperature and pressure. From these readings and reference measurements the calibration constants (NT25, mT, NT/NP700,25, mp) are calculated (658).