Inductive sensor responsive to the distance to a conductive or magnetizable object

US5504425A · kind A · utility

Assignee

• Gebhard Balluff Fabrik feinmechanischer Erzeugnisse GmbH & Co. · DE

Inventors

• Sorin Fericean · Leonberg, DE
• Michael Friedrich · Wolfschlugen, DE
• Ernst Gass · Herznach, CH

Key dates

• Filing date: May 24, 1994
• Grant date: Apr 2, 1996
• Expiry date: May 24, 2014

Classification

• Technology area (CPC G): Physics
• CPC primary: G01V3/102
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

In order to improve a sensor for detecting an electrically conductive or netizable object with an oscillator comprising a resonant circuit including an inductance and a capacitance, the resonant circuit impedance depending on a damping distance between the inductance and the object and rising steeply in the range of small damping distances, further rising less steeply in the range of medium damping distances and substantially having a constant value in the range of large damping distances, and a closed adaptive loop stage supplying a loop current for the resonant circuit and generating a course of an amplitude value dependent on the damping distance, and an evaluation circuit detecting an oscillator voltage applied to the resonant circuit, such that the oscillator also oscillates in the range of small damping distances and has a characteristic curve, with which the oscillator voltage varies with the damping distance also in the range of small damping distances, it is suggested that the course of the amplitude value of the loop current in the range of small damping distances has at least one oscillation-maintaining segment, the gradient of which is smaller than the gradient of the c…