GB271811A - Improvement in electrical instruments - Google Patents

Abstract

271,811. Engelhard Inc., C., (Assignees of Krueger, R. H.). May 29, 1926, [Convention date]. Thermometers.-In gas testing apparatus of the thermal conductivity type in which a resistance or heating wire is wound around a tube of fused. crystal quartz and is inserted into a gas cell, the resistance units are arranged in pairs in adjacent gas cells and are connected in a Wheatstone bridge so that the analysing and comparison units are in alternate branches of the bridge. Fig. 1 shows a gas cell tube 1 having inlet and outlet openings 2, 3 for the circulation of gas through the tube, in which is mounted the resistance, or heating wire 4. This is enclosed in a, sheath 5 or capillary tube of fused crystal quartz. The ends of the tube 1 are hermetically sealed by plugs 6, 7 of cement &c., The wire, 4 may be of platinum, nickel, pure iron, &c. In the construction shown in Fig. 3, a block 8 of copper &c. is provided with a conduit 9, for the gas to be tested, and a chamber 12 communicating with the conduit 9 by shunt passages 10, 11. Two such chambers 12 are provided. one for the test gas to be analysed and one for the comparison gas. Each is provided with a pair of resistance or heating elements 13 secured in place by a nut 14 and sealing cement 15. Each resistance thermometer 13 comprises a tube of fused quartz sealed at one end 16 and containing a coil of resistance wire 18 in contact with the walls of the tube, the inner end of the wire being carried back through the centre of the coil. In an alternative construction of resistance, the wire is wound on the external surface of a quartz tube. through which the gas is passed.