CURRENT CONTROLLER FOR RESISTIVE HEATING ELEMENT

A controller for regulating current flow through a resistive heating element in order to adjust the temperature thereof is disclosed. The controller includes a means for periodically measuring the resistance of the heating element. During controller calibration, the rate of change of the measured heating element resistance is ascertained in order to determine whether the heating element is at ambient temperature. Computations are performed on the value of the measured heating element resistance associated with ambient temperature conditions, enabling the controller to predict the value of the heating element resistance at a desired temperature. Current is then conducted through the heating element to generate heat, while periodic measurements of the heating element resistance are performed. The resistance values obtained during these latter resistance measurements are compared with the predicted resistance of the heating element associated with the desired temperature and the difference between the predicted resistance and each measured resistance is used to generate a control signal which regulates the flow of heating current through the heating element until desired temperature is reached.