GB1259143A - - Google Patents

Abstract

1,259,143. Measuring temperature. INTERNATIONAL STANDARD ELECTRIC CORP. Sept.4, 1969 [Sept.11, 1968], No.43796/69. Heading G1N. [Also in Division G3] In apparatus for temperature control, a first switching process is initiated when a pre-selected temperature is reached and, for pre-selected temperatures above a certain value, upon initating said first switching process there is also effected a modification to the temperature detector circuit so that it then responds to a second response temperature, upon reaching of which there is initiated a second switching process. Fig.1, shows a circuit for controlling the temperature of lye in a washing machine and for switching on a vapour extractor if the selected lye temperature is above a certain value. When N.T.C. resistor 1 reaches the temperature selected by switch 2, transistor 8 in the diagonal of the bridge circuit becomes conducting and relay 11 is de-energized to cut off the heating. If switch 2 is in zone b, representing a selected temperature below said certain value, the heating remains off until the lye has cooled sufficiently for transistor 8 to become blocked. If switch 2 is in zone a, representing a selected temperature above said certain value, relay 12 becomes energized, holding itself on through contacts 12a and changing over contacts 12b to substitute a different resistance in the bridge circuit so that transistor 8 becomes blocked and heating is resumed until the selected temperature is reached. In an alternative arrangement Fig. 2 (not shown), a transistor switch (16) performs an analogous function to that of contacts 126 in Fig.1, if the selector (2a) is set for a temperature above a certain value.