GB576366A - Improved arrangement of a thermocouple for use in connection with high frequency electric heating apparatus - Google Patents

Abstract

576,366. Electric thermometers. BRITISH INSULATED CABLES; Ltd., QUAYLE, J. C., and JONES, P. March 22, 1944, No. 5334. [Class 97 (iii)] [Also in Groups XI and XXXV] One of the supply lines of apparatus for heating a body by a high frequency induction is a tubular conductor 3 enclosing a thermocouple conductor terminating in a hot junction at the end of conductor 3 where it is coupled to a heating electrode 1 or to a high frequency coil and the thermocouple conductor extends within conductor 3 to an earthed point thereof, where it is brought out to separate the high frequency system from the thermocouple system. The conductor 3 is of copper and may form a conductor of the thermocouple, the other conductor of which is a wire of copper-nickel alloy, such as that known under the Registered Trade Mark "Eureka ". The tubular conductor 3 may enclose several thermocouples connected in series, the hot junctions being separately secured in an insulating block of mica-filled glass in the electrode 1. of the heating condenser. High frequency oscillations are fed from a valve oscillator circuit 8 to a hollow helical coil 6 forming the secondary winding of a coupling transformer, the coil 6 being connected at one end to an earthed screen 5 and at the other end to conductor 3 insulated at 4 from the screen 5 through which it passes. The conductor 13 of the thermocouple is insulated in the tube 3 by cup-shaped beads 12 and is soldered to the electrode. The thermocouple conductor brought out at the earthed end of the tube 6 are led through a high frequency filter 26 to a cold junction 17 in a Dewar flask 18, a milliammeter 19 being inserted.