| 摘要 |
A temperature increase or excursion sensor and locator consisting of a temperature sensitive cable which includes three electrical conductors, two conductors are separated by a dielectric member to form a linear strip capacitor and one of the two conductors has a number of thermostatic devices connected serially. Over or under temperature excursions are sensed and located by the cable when it is connected to control electronics by detecting the continuity and by measuring the capacitance of the cable. Under normal conditions, all of the thermostatic devices are electrically conducting and the control electronics measures the full capacitance from both ends of the cable and detects continuity over the full length of the cable. Upon a temperature increase or an excursion, one or more thermostatic devices become non-conductive, creating a discontinuity in one of the conductors and in addition the resulting capacitance is proportionately reduced. Presence of the temperature excursions is detected by the control electronics which senses a loss in continuity in one of the conductors. The presence and location of the excursions are also indicated by the control electronics which from each end compares and ratios the reduced capacitance to the full cable capacitance. The respective ratios of said capacitances determine the distance of the temperature excursions from each end of the cable.
|
