GB1236825A - Instruments for measuring the magnetic susceptibility of a mixture of gases, particularly of a mixture the oxygen content of which varies rapidly - Google Patents

Abstract

1,236,825. 825. Measuring oxygen content electrically. HARTMANN & BRAUN MESS UND REGELTECHNIKA.G. Aug. 23, 1968 [Aug. 31, 1967], No. 40453/68. Heading G1N. Apparatus for determining the oxygen content, in a mixture of gases comprises a gap 4 in amagnet 1 on which is an energizing winding 2 supplied with a pulsating direct current from a diode 3 and an A.C. supply, which gap is filled with samples of a test gas flow, 7, and a reference gas flow, 8, through valves 9, 10 respectively and is exhausted through a discharge tube 13 so that mixing occurs only in the uniform field regions, none occurring at the junctions between the gap and the feed tubes, 11, 12, at which are created non-uniform field regions the resultant differential pressure, registered by capacitor microphone, 21, providing a measure of the relative magnetic susceptibilities. The differential pressure variations are coupled to a detector, 24, synchronized from an auxiliary winding 25 and displayed on a chart recorder, 26. For gas pressure less than atmospheric a suction pump, 17, exhausts the chamber through valves 14, 16 and buffer stage, 15, pressure being indicated by U-tube 18. To reduce errors arising from magnetostriction and/or core vibrations an analysis chamber is of rigid mechanical structure comprising two soft-iron sheets (34, 35) Fig.2 (not shown) fitted tightly between the parallel poles of the magnet and is sealed by abrass frame (36) compressed between them the core 1 being constructed of high permeability laminations. Vibration effects may be further reduced by mounting the analyser chamber separately from the magnet. In another embodiment, Fig. 5, where no reference gas is available, a reference gas is provided from the carrier gas in a feed tube, 45, heated by an element 47 and supplied with the test gas, the measurement being carried out as described above. The instrument may be further simplified provided the heated gas may be cooled to its original temperature before passing through the heterogeneous zone 44 by supplying test gas through the valve 54 only, discharging it through the valve 55 and dispensing with items 56, 57 and the tube between valves 54 and 55.