Electricity: measuring and testing – Magnetic – With compensation for test variable
Patent
1979-04-06
1981-05-12
Strecker, Gerard R.
Electricity: measuring and testing
Magnetic
With compensation for test variable
324207, 324236, 336179, G01R 3300, G01N 2772, G01B 714, H01F 1516
Patent
active
042675081
ABSTRACT:
An apparatus for non-contact measurement of the distance or gap between a detection coil and a metallic body arranged in an opposing relation with the detection coil, includes a differential amplifier having one input terminal connected to a reference oscillator and the other input terminal connected to a feedback circuit. The detection coil comprises a cylindrical coil and a plurality of magnetic members in rod form are arranged inside its inner bore along the direction of the coil axis and adjacent to the coil inner wall. The plurality of magnetic members comprise a combination of those having positive temperature characteristic and others having negative temperature characteristic so that a change with temperature of the permeability of the magnetic members as a whole is practically reduced to zero. The feedback circuit incorporates the amplified differential output signal of the differential amplifier and the detection coil so that the feedback input signal to the other input terminal of the differential amplifier is controlled by the impedance value of the detection coil which varies with a change in the distance. Consequently, the differential amplifier generates a differential output signal which is indicative of a measured distance.
REFERENCES:
patent: 2707001 (1955-04-01), Hathaway
patent: 3195086 (1965-07-01), Taylor
patent: 3209292 (1965-09-01), Montross
patent: 3843945 (1974-10-01), Koning
patent: 4030027 (1977-06-01), Yamaoa et al.
Nippon Kokan Kabushiki Kaisha
Strecker Gerard R.
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