TERMOREGOLATORE

The electric pad heater (1) is coupled into one branch of an electric bridge circuit, whose second branch is temp.-sensitive and consists of resistors (7,8,9). The output diagonal of the bridge is coupled to the input of a thyristor (5) over a resistor (10) in the base-emitter circuit of a transistor (11). The collector is coupled to a second transistor base with the emitter-collector coupled into the bridge. The bridge is balanced by a setting potentiometer (8), and at the set temp. no current flows in the control circuit of the thyristor. As the temp. if reduced, a small current is generated across the thyristor coupled resistor, coupled to the transistor circuit, which opens and bridges the heating resistors (7,8) to produce a current increase in the thyristor control circuit, which causes the thyristor to conduct and proVide heating.