| 摘要 |
<p>FAULT DETECTING SENSOR AND METHOD OF DETECTING FAULTS THEREWITH This invention relates to sensors for detecting a fault condition, e.g. excessive temperature or leakage of fluid, in a large apparatus, and to methods of using such devices. The novel sensors comprise a conductor, an element composed of a conductive polymer whose resistivity increases sharply when a fault condition occurs, and a dielectric element which separates the conductor and conductive polymer element so that they form an electrical capacitor. The sensor is in the form of a sheet or cable whose capacitance is periodically measured. When a fault condition occurs, the conductive polymer element increases sharply in resistance in the region of the fault and reduces the capacitance of the sensor, thus signalling the occurrence (and preferably also the location) of the fault. Figure 1 shows a typical sensor in the form of a cable comprising a central conductor 10, a dielectric layer 12, a PTC layer 14 and an outer protective layer 16. The invention is particularly useful for detecting localised overheating, e.g. in dryers for agricultural products, or leakage of a fluid, e.g. for a conduit.</p> |
