Electrical immersion heater control - has microprocessor with memory which controls operation of contactor to supply power to heating element

摘要

The immersion heater tank element is connected to the mains supply by a solenoid-operated switch (13). The inputs to the electronic temp. control system are provided by a temp. detector (10) set into the side of the tank, and a rotatable temp. demand control (12). The temp. detector output is fed to a demand value comparator, a max. temp. comparator and a min. temp. comparator. The demand comparator output is converted to digital form and fed to the processor, a memory, a start-up circuit and the output register. The output is fed, together with the max. and min. signals, to a gating circuit which drives the solenoid (13) via an amplifier.