| 摘要 |
An electrical heater element 3 includes sense wires 2,4 located at a point or points between the power terminals 1,5 that provide a voltage signal that is compared with predefined levels or ratios, to trigger a safety indicator or power supply trip if the sensed voltage falls outside a predetermined range. The element can be a planar element such as a heating pad comprising a conductive sheet, mesh or fabric or moulded into a three dimensional form. The sensed signals can be periodically masked to allow settling before tripping and used to regulate power using pulse width modulation and to indicate temperature. The controller 18 can also trip in response to over-current and to a screen voltage. The planar element can be used in electric blankets, heated garments, diving suits and boots. |
