Control of temperature in laboratory thermostatic bath

摘要

The process controls laboratory thermostatic bath systems. Supply of power to the heater is controlled using a pulse width modulation (PWM) technique to switch the alternating current. A semiconductor switch controls current delivered to the heater in successive pulse periods. There are n basic power settings. Each is a fraction, 1/n, of the heater (i.e. element) nominal power. These settings are adjustable by additional control of the semiconductor. Basic power adjustment is effected over successive periods, each amounting to a fraction of the pulse period and comprising at least n half waves.