Self-Controlled Variable Resistance Heating System

The use of a variable resistance heating element to monitor the temperature of work and control heat input to the element is described. A solid-state controller that measures the element temperature by continuous monitoring of the element resistance i used to control the voltage input to the element. This eliminates separate temperature measuring device such as thermostat, thermo couple, or thermistor and associated wiring. In addition, the average temperature of the work is measured rather than the temperature of a single location.