Method and apparatus for real time monitoring of an electric furnace heating coil

摘要

Heating coils used in an electric furnace used to process semiconductor wafers are monitored on a real time basis by sensing the AC current in a power line delivering electrical power to the furnace. The AC current is sensed by a coil positioned around and magnetically coupled with the power line. The sensed AC current induces an AC voltage in the coil which is converted by an electrical circuit into a DC voltage. The DC voltage is used to control a solid state relay that generates an alarm signal when the value of the DC voltage is less than a preselected value indicating that an open circuit is present in the heating coil.