Apparatus for measuring the thickness of the ferromagnetic sheets, such that the sheets of iron - white

摘要

1,097,179. Measuring thickness electromagnetically. TELEDICTOR Ltd. April 1, 1966 [July 21, 1965], No. 30990/65. Heading G1N. The thickness of a ferromagnetic sheet is measured indirectly by saturating it magnetically in the direction of its plane faces and measuring the total flux passing through it, which is proportional to the sheet thickness. The plate D is placed on a flux cylinder 13, Fig. 1, resting on the upper surface of a cylindrical permanent magnet 10, sufficiently strong to saturate the sheet, the magnetic circuit being completed by a flux plate 11 which is sufficiently large not to be saturated. The flux passing through the plate D is measured by a search coil 121 wound round a laminated core 12 having a square loop characteristic and a constant incremental permeability. The annular gap between the core and cylinder 13 is filled with a non-conducting plastics material (17), Fig. 3 (not shown), e.g. polyester resin cured in situ. In operation an A. C. e. m. f. is applied to the search coil 121, serially connected to a resistance 141 which is connected across an amplifier 14 designed to amplify only unidirectional pulses of an alternating current. The unidirectional pulses across the resistance 141, having amplitudes proportional to the flux in the core 12 and therefore to the thickness of the plate (due to the properties of the core 12), are transmitted to the scanning coils of a CRO 15 to deflect its beam from a zero point 0 of a scale 16, calibrated in steel thickness. In a modification, the magnet 10 may be replaced by an electromagnet and the cylinder 13 may be omitted. Further, more than one search coil may be used.