Proximity sensor with reduced temperature sensitivity using A.C. and D.C. energy
US5180978A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 2, 1991 |
| Grant date | Jan 19, 1993 |
| Priority date | — |
| Expiry date | Dec 2, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/101
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A proximity sensor is provided with a means for directly measuring parameters of a proximity sensor coil which permit the determination of both the AC and DC resistances of the coil. These parameters are then used to determine a discriminator value magnitude according to a mathematical relationship that has been predetermined through previous analysis of empirical data for the particular coil and application intended for the proximity sensor. In one particular application of the present invention, the rear AC resistance is utilized and is added to the DC resistance after the DC resistance has been mathematically altered by a preselected factor. Alternative embodiments of the present invention can also utilize the imaginary AC component of the impedance either by itself or in conjunction with the rear AC component of the impedance. Whether the real or imaginary AC components of the impedance are used individually or together, the DC resistance is used in the determination of the discriminator value magnitude because of its reliable relationship to the temperature of the coil.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.