GB1279091A - Devices for the measurement and control of magnetic field strength - Google Patents

Abstract

1279091 Magnetometers NEWPORT INSTRUMENTS Ltd 8 Aug 1969 [8 May 1968] 21834/68 Heading G1N In a magnetometer of the type in which the force on or displacement of a current carrying conductor in the field being measured is measured, stationary capacitor plates co-operate with the conductor or a plate attached thereto for sensing displacement of the conductor. As shown in Fig.1 a current I, which may be direct alternating or intermittent, is passed through arm 15 and the torsional displacement or torsional oscillations of arms 14 and 15 is sensed by differential capacitors 16, 17 and 18, 19. If A.C. is used, its frequency may coincide with the resonance frequency of the structure 10. Excitation periods may be alternated with measurement periods. E.M.F.s induced in one or more of the conductive paths may be compared with the capacitive measurements. Electrostatic forces may be used to achieve a null balance. Part of the vane structure may be electrically isolated from the rest of the vane so that the electrical charge on this part (40) Fig.4a (not shown) remains constant whereby electrical repulsion forces may be used. Other configurations of vanes are described with reference to Figs.3a to 4a (not shown). In Fig.5, coils 55, 56 are mounted on a part 57 supported by bearings 60, 61. Leads to the coils and to capacitor plates 58, 59 may be in the form of springs controlling the position of the moving structure. In another arrangement, Fig.6 (not shown) four conductive paths (66, 67, 68, 69) are attached in pairs to opposite faces of an insulating strip (70), a respective capacitor plate being positioned opposite each path. A stationary conductive loop 77 responds to variations in time of the magnetic field.