Power control device for temperature control.

摘要

A power control device for controlling power to resistance heaters (2, 20) in a chamber (1) in which the temperature is to be controlled and a pressure tank (19) uses a microprocessor (7) adapted to provide a temperature setting means (8) which inputs a desired temperature. The power consumed by the heater in the chamber is measured by a circuit (10, 12, 11) and compared with a desired power level calculated by the microprocessor. Temperature measuring means (4) in the chamber (1) provides a signal compared with the desired temperature. The microprocessor synchronizes an A.C. current signal and allows a triac (17) to fire for a calculated portion of each phase of A.C. current to provide power to the heater in the chamber such that the temperature therein is accurately controlled and maintained. When subambient temperatures such as -150 DEG C are required the microprocessor controls another triac (28) in a similar manner to control power to the heater in the pressure tank which contains coolant for feeding to the chamber. The pressure in the tank is monitored and compared with a desired pressure level calculated by the microprocessor.