Patent GB-1486462-A (GB)
Title: Oscilloscopic ferrometers
IPC: G01R33/14
Filed: 1974-09-17
Abstract: 1486462 Measuring magnetic characteristics V M MOGILEVSKY N F DERIGA V P EKIMOV A P ERASTOV V V POSOKHIN and B E FURER .17 Sept 1974 40356/74 Heading G1N In a magnetic characteristics e.g. hysteresis loop, measuring apparatus the sample is magnetized by two ellipsoidal solenoids separated by an air-gap I the geometric dimensions of each of which satisfy the relationships RL/L = 0À1368 K<SP>3</SP> + 0À0822 K<SP>2</SP> + 0À7618 K + 0À007 and K= 1À108(1/L)<SP>0À6415</SP> where K is in the range of 0À1 to 0À9, RL is the radius of the effective opening at the air-gap end of the solenoid, L is equal to one half of the axial length of the solenoid and k is the ratio of the small axis to the large axis of the ellipsoidal envelope. As shown in Fig. 1 the two solenoids 1, 2 are each formed by a tubular conductor 3 which are connected in series across a hollow single turn winding 5 of a step-down toroidal transformer 6 and to a hollow connector 8 which acts as a water supply manifold to enable cooling water to be passed through the solenoids and secondary winding. The sample 7 to be measured is mounted along the longitudinal axis of the two solenoids and a flux density pick-up coil 12 is coupled thereto, the output being coupled via an adder to the series connection of integrator 25 and phase corrector 27. In order to compensate for the airgap between pick-up coil 12 and sample 7 a pair of current compensation coils 14, 15 are provided as shown and which are connected in series opposition with pick-up coil 12, voltage compensation coil 13 and amplitude phase correctors 16, 17, 21. The intensity of the magnetic field applied to the sample 7 is sensed by winding 29 coupled to the single turn secondary 5 and which is connected to the series combination of integrator 30 and phase corrector 32. A short-circuited screen 33 of non- magnetic material is provided to damp parasitic oscillations.  Hysteresis loop measurement: 38 The outputs from phase correctors 32, 37 are applied to amplitude modulators 55, 56 which are controlled by gate pulses from circuit 34, and converted to D.C. by detectors 57, 58. The D.C. outputs on lines 39 and 40 are applied to meters 42, 41 graduated in flux density and magnetizing field strength. Permeability, Susceptibility: 43 The signals obtained at the inputs to integrators 31, 26 are fed to the inputs of modulators 59, 60, gated by signals from circuit 34, and the outputs of which are amplitude detected at 61, 62. Detectors 61, 62 are connected to keying circuit 63 and amplitude modulator 67 controlled by the output from flip-flop 65, one input of which is connected to timing pulse generator 66 and the other input to voltage/time convertor 64. The output of modulator 67 after filtering at 68 is fed on line 44 to meter 41 also graduated in permeability. Electromagnetic losses: 45 The output from phase corrector 32 and the input to integrator 25 are fed to adder circuits 69, 71 feeding squares 70, 72 the outputs from which are subtracted at 73 and then integrated. The output of the integrator 74 is connected via line 46 to meter 41. CRT Display The gating pulses from unit 34 are fed to the control electrode 36 of CRT 37 and the outputs of integrators 25 and 30 are fed via an automatic switch 49 to the two sets of deflection plates 48 of tube 37, scale marked co-ordinate axes of magnetization and intensity being formed on the CRT by deflection pulses formed by unit 47 and fed via switch 49 to the deflection plates. Remanence Switch 49 is operated so that a combination of a hysteresis loop and its mirror reflection with respect to the J axis is displayed on the screen 97. The points of the intersection along the J axis of these loops is then determined and the value for remanence read from meter 41. Demagnetization of the sample may be tested at the same time.