Apparatus for non-contact measurement of distance from a metallic body using a detection coil in the feedback circuit of an amplifier
US4267508A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 6, 1979 |
| Grant date | May 12, 1981 |
| Priority date | — |
| Expiry date | Apr 6, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01F27/008
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
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 differenti…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.