GB353875A - Improvements in and relating to apparatus for controlling and measuring temperature - Google Patents

Abstract

353,875. Thermostats. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Koller, L. R.; 1138, Sumner Avenue, Schenectady, New York, U.S.A.) April 24, 1930, No. 12693. Convention date, April 24, 1929. [Class 64 (ii).] In controlling or measuring temperature in the range 80-150‹ C., an electric discharge device is used, the evacuated envelope of the device containing a cathode having a layer of alkali material emitting an effective thermionic current varying with the temperature. In heating liquids, the discharge device 1, Fig. 4, is inserted into the heat-insulated liquid-container 14 and is connected in circuit with a source 18 of electric current and with a current meter 19. The meter is calibrated to read temperatures or controls the fuel supply to a burner heating the liquid. The discharge device may have a standard four-pin cap 3, Fig. 1, one pin being connected to the central anode 5 and the other pins being dummies. The cathode 4 is coated on the inside of the envelope 1 and is connected to a sealed lead 7. In forming the cathode, silver or platinum may be dispersed on to the glass, or a solution containing silver, platinum or graphite may be painted on prior to depositing silver electrolytically. After baking, the silver is oxidized by a high-voltage discharge in oxygen, the oxygen is removed and caesium or rubidium is then freed by heating by high-frequency currents a capsule 9 containing caesium dichromate and silicon. The cathode so formed may comprise caesium oxides and may be activated by maintaining for several minutes at 200‹ C. In a modification, the cathode is within the envelope and the alkali layer is deposited on a copper, nickel, tungsten molybdenum, silver or silvercoated electrode in the form of a semi-cylinder, a flat plate or several angularly-disposed plates. Specification 303,476, [Class 39 (i), Electric lamps, Arc &c.], is referred to.