| 摘要 |
<p>A proximity sensing system including an improved variable inductance measuring technique to provide an indication of the proximity of a target object to a remote sensor unit 10 which includes a sensor inductor. A variable inductance measuring apparatus measures the inductance of the sensor inductor, which inductance corresponds to the proximity of a target object. The variable inductance measuring network includes a sensor current pulse generator 20 which, in each of successive system periods, establishes a time-varying current through the sensor unit 10. A sensor control loop stage 30 senses when the resulting sensor voltage reaches a predetermined level and then captures the sensor current so as to clamp the sensor voltage at this level. A retrieval stage 40 then determines the rate of change of the sensor current at the time the sensor current is zero, establishing a calibrated analog voltage of the inductance of the sensor inductor which is substantially temperature independent. The inductance analog voltage is applied to a proximity detection and switching stage 50 which provides a quantized target-near detection pulse if the inductance analog voltage corresponds to a threshold proximity of the target object. Integration over successive system periods then provides a time-average proximity voltage which is applied to a Schmitt trigger and proximity switching network 58, the output of which indicates the proximity of the target object to the sensor inductor with respect to a threshold actuation gap.</p> |
