GB1461574A - Temperature-sensing probes - Google Patents

Abstract

1461574 Temperature sensing devices SMITHS INDUSTRIES Ltd 22 March 1974 [26 March 1973] 14480/73 Heading H1K A temperature sensing probe comprises a tubular shell within one end of which a sensing element is located and a cable for making electrical connection to the element extending therefrom lengthwise of the probe along a helical path against the inside surface of the shell and being bonded thereto at least at spaced points along that path. As described the element is a thermocouple formed by joining inner conductors 10, 11 of a metal-sheathed magnesium oxide insulated cable 12 (Fig. 1). In manufacture, after forming the couple and sealing the sheath at a point beyond it, the cable is wound to the required form on a mandrel, coated with brazing material, and push-fitted into steel tube 1. A cup-shaped element 7, a cap 17 apertured as shown and seal 13 are put into position and the assembly heated to 1075‹ C. to braze the cable and the cap and element 7 to the shell to give a vibration-resistant construction. Thermal stresses are reduced by making shell 1 and the cable sheath of expansion coefficient matched materials, e.g. specified nickel chromium and nickel-chromium-iron alloy respectively, the inner conductors of the cable preferably being of nickel-chromium and nickelaluminium alloy respectively. Adhesive placed at spaced points along the cable may be used instead of brazing. A cable with a plurality of pairs of inner conductors, or a plurality of cables each with one pair, may be used to provide a number of thermocouples and in an alternative form the probe shell or sheath of the cable may constitute one limb of the couple or couples.