Patent ID: 6023052
Filing Date: 2000-02-08
Classification: G05D,H05B

Abstract:
A control system for controlling parallel heater elements comprising:a plurality of electrical heater elements;a plurality of temperature sensors associated with a plurality of the heater elements, the temperature sensors effective to generate temperature signals;at least one temperature controller effective to generate a control signal based on at least one temperature signal;an alternating current power supply connected to the electrical heater elements through a power transmission system;a zero detection circuit effective to generate a signal when the voltage of the alternating current power supply passes through ground potential;a firing controller that will block electrical power to a heater element, starting when a zero detection signal is detected an ending when another zero detection signal is detected, for a fraction of the alternating current cycles in a time period, the fraction being a function of the control signal;a remote modem in the proximity of the heater elements effective to convert the temperature signals to signals transmitted through the power transmission system and to detect a control signal transmitted through the power transmission system; anda master modem effective to convert the control signal to a signal transmitted through the power transmission system and to detect temperature signals transmitted through the power transmission system.