GB868545A - Device for measuring magnetic properties - Google Patents

Abstract

868,545. Magnetic tests; determining physical qualities of materials. VYZKUMNY A ZKUSEBNI LETECKY USTAV. Feb. 27, 1958 [Feb. 27, 1957], No. 6433/58. Class 37. A magnetic testing probe comprises a single core of magnetically soft material carrying a magnetizing winding and two identical pick-up windings spaced apart and connected in opposite sense, the complete probe being contained in a case of electrically conductive non-magnetic material. Fig. 7 shows an open core 1 having a primary winding 2 fed from an alternating current source 11 and two secondary windings in opposition connected to terminals 5, 6. The apparatus is shown measuring the coercive force of a ferromagnetic sheet 9. The sheet 9 is first radially magnetized by bringing one pole of a magnet into contact thus providing the flux - Hc, + Hc approximately equal to the coercive force. The probe 10 is brought into position so that the two secondary coils are linked by opposing flux. This results in an induced voltage at the frequency of the second harmonic which is fed to the amplifier detector 12 coupled to an instrument 13 which may be calibrated directly in terms of coercive force. The secondary winding may be tuned to the second harmonic by means of capacitor 14. Fig. 8 shows a method of determining the coercive force of a previously magnetized sample 15 using the demagnetizing method. The probe 10 is brought adjacent the sample 15 and at right angles to the magnetic axis so that the two secondary windings are traversed by opposing flux. The direct current in a solenoid 16 is then increased until the sample 15 is demagnetized. Reference is made to the use of the probe in the measurement of susceptibility or in the detection of flaws in material. Fig. 4 (not shown) relates to a probe having a closed circuit magnetic core.