GB870071A - - Google Patents

Abstract

870,071. Electric measuring systems. VYZKUMNY A ZKUSEBNI LETECKY USTAV. March 6, 1959 [March 7, 1958], No. 7852/59. Class 40 (1). [Also in Groups XXXVI and XXXIX] Apparatus for measuring a voltage comprises a group of four toroidal coils wound as for a magnetic amplifier, associated with a cylindrical magnetic cover, a single-turn winding on the assembly producing an A.C. flux in the cylinder when one set of toroidal windings is energized, the interconnections between the windings being such that the test voltage applied to another set of windings upsets an initial electrical balance condition, energizing a motor which applies a torque to the cylindrical cover, thereby inducing a voltage in a solenoid winding by magnetostriction, which is used to rebalance the system. Construction (Figs. 1, 2). Four coaxial toroidal cores 11-14, each wound with five windings 21-51 &c., are arranged inside a magnetic cylinder 86 which is extended to form a narrow portion on which is wound a solenoid coil 10. The ends of the cylinder 86 are covered by plates 80, 82 interconnected by a rod 81 passing through the centre of the assembly. End-plate 80 is attached to a base-plate 8, and end-plate 82 carries a horizontal rail 84 on which a carriage 90 is located, movable by a motor 71 via a cable 6, the carriage carrying a pen 95 for recording its movement on a chart 99. Electrical circuit (Fig. 4).-Windings 21-24 are fed with A.C. to produce an alternating magnetic flux in each core 11-14, on which is superposed a unidirectional magnetic flux by windings 31-34. The end-plates 80, 82, the central rod 81 and the cylinder 86 form a single turn coupling with all the toroidal cores, and produces a cylindrical flux in the cylinder 86. When a D.C. voltage to be measured is applied to windings 51-54 it increases the flux in two cores, e.g. 11, 12, and decreases the flux in the other two cores, whereby the impedance of coils 21, 22 is decreased, and that of coils 23, 24 is increased, the unbalance between the pairs causing a current to flow through winding 710 of motor 71, which drives the carriage 90 and associated weights 93 to produce a torque on cylinder 86. Due to the magnetostrictive effect on the cylinder, a voltage is induced in pick-up coil 10 which is rectified at 220, 230 and flows through windings 41-44 to rebalance the circuit, the rebalancing being enhanced by the current in windings 61-64. Thus the distance travelled by carriage 90 is proportional to the voltage applied to windings 51-54, and is recorded on the chart 99. The apparatus may be used to measure a force applied to the rail at a fixed distance from the point of suspension, and automatically rebalancing as above by moving the carriage 90.