| 摘要 |
Overheating alarm for surveillance of heat emitting objects, preferably intended for surveillance of hotplates and electric cookers. Emitted heat radiation from a monitored object is detected by an IR-detector, located at a distance from the monitored object, which transmits a warning signal and/or interrupts the electric current supply when the temperature for a monitored object exceeds a predetermined maximum temperature level. The IR-detector is preferably arranged with a highpass filter, which by means of absorption or reflection reduces radiation having shorter wavelengths than 1 - 3 mu m from influencing in the IR-detector included detector element, and a shortpass filter, arranged to reduce radiation having wavelengths exceeding 3 mu m. The detector element comprises advantageously of two bridge circuit connected thermistors, integrated with a smoke detector. Compensation for radiation caused by adjacently located light sources is performed by differential measurement in the visible and near IR-range. |
