GB1220413A - Improvements in and relating to gas analyzers - Google Patents

Abstract

1,220,413. Paramagnetic gas analyzers: force balance arrangements. SAMOSTOYATELNOE KONSTRUKTORSKO - TEKHNOLOGICHESKOE BJURO "MEDFIZPRIBOR". June 25, 1968, No. 30161/68. Heading G1N. In a paramagnetic gas analyzer of the type in which the torque on a body suspended in a non- uniform magnetic field in a space containing the gas being analyzed is counteracted by an electrical force balance arrangement, the input of the force balance is derived from at least one magnetoresistive element mounted on the body and connected in a bridge circuit. As shown in Fig. 1, two magnetoresistive elements 7 of bismuth or indium antimonide are connected in an A. C. bridge circuit including resistors 9. The bridge output is amplified (11), rectified (12) and fed to a coil 5 to produce a restoring torque on the body 4. The plane of coil 5 is perpendicular to the direction of the magnetic field. In a second arrangement, Fig. 4, that part of the bridge circuit including the magnetoresistive elements 7 also serves as the coil 5<SP>1</SP>, A. C. being used to detect rotation of the body 4 and D.C. for restoring the body to its zero position. In a further arrangement Fig. 5 (not shown) four magnetoresistive elements are used in the four arms of the bridge which also serves as the restoring coil. Alternatively Fig. 7 (not shown) for magnetoresistive elements are connected in pairs in two arms of the bridge.