GB637497A - Improvements in or relating to the manufacture of resistors comprising a liquid high resistance medium - Google Patents

Abstract

637,497. Liquid resistances. GENERAL ELECTRIC CO., Ltd., GOSSLING, B. S., SOUTER, L. S., and PHILLIPS, N. M. June 22, 1948, No. 16756. [Class 37] A liquid resistor, Fig. 2, comprising an envelope formed by a glass tube 1 and tubular platinum electrodes 2, 3 and containing a liquid high resistance medium having a water content, for example a mixture of toluene, ethyl alcohol picric acid with a small amount of water, is characterized in that the internal surface of the envelope as a result of treatment fully described in the Specification is so conditioned in regard to water absorption, i.e. water content, as to be in water equilibrium with the liquid resistance medium 8. This feature it is stated ensures stability of resistivity and temperature coefficient which latter is made zero by suitable proportioning of the ingredients in the medium 8. A coating of silicone on the outer surface of the glass tube 1 prevents surface humidity effects. The internal surfaces of the platinum tubes are coated with platinum black to suppress polarization effects. In Fig. 2 the platinum tube 3 is dimpled at 10 trapping vacuous space at 9 so that liquid cannot flow into 9 in any position of the envelope, but can expand into the space when heated. In a modification, the dimpling is omitted and the vacuum space appears as a bubble free to move along the length of the envelope, but in this case the resistor must be so mounted that the bubble is located inside one of the platinum tubes 2, 3. The latter are wound with double wire 11, 12 with the free ends of the wire forming leads 13, 14 passing through holes 17, 18 in cupro-nickel end caps 15, 16.