Electricity: measuring and testing – Magnetic – Displacement
Patent
1991-09-30
1994-04-12
Wieder, Kenneth A.
Electricity: measuring and testing
Magnetic
Displacement
32420712, 32420715, G01B 714, G01N 2790
Patent
active
053028945
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a noncontacting displacement measuring system, comprising a sensor with a measuring side and a connection side, an electronic supply/evaluation unit, and a cable leading from the sensor to the electronic supply/evaluation unit and having preferably two inner conductors, with the sensor comprising a housing, at least one coil arranged in the housing, connecting lines leading from the inner conductors of the cable to the coil or respectively coils, and, if need be, an embedding substance which anchors the coil or respectively coils and the connection lines.
For years, noncontacting displacement measuring systems of different types have been known from the practice. They can be classified by their basic mode of operation, first, into displacement measuring systems on the basis of eddy currents, and inductive and capacitative displacement measuring systems, and, second, into optical or acoustical displacement measuring systems.
The present invention relates to a noncontacting displacement measuring system comprising a sensor with at least one coil, i.e., displacement measuring systems, which operate either on eddy-current basis or by induction.
In displacement measuring systems operating by the eddy-current measuring method, a high-frequency alternating current flows through a coil normally cast into a housing, which forms an oscillating circuit by the parallel connection of capacitances. In this process, an electromagnetic field emanates from the coil. This field induces eddy currents in a conductive object, which withdraw energy from the oscillating circuit. Primarily at higher operating frequencies, a reaction of the induced eddy currents appears, which changes as a back induction the real part of the impedance of the coil. The influence on the imaginary part of the coil impedance is, in this process, dependent on the magnetic characteristics and the operating frequency. Nonmagnetic objects of measurement reduce the inductance of the coil when approaching the latter.
The amplitude of the oscillating circuit changes as a function of the spacing. Demodulated, linearized, and amplified, if need be, the change in amplitude supplies a voltage which varies proportionally to the spacing between the sensor and the object of measurement.
In the case of the inductive measuring method, the coil arranged in the sensor is likewise a part of an oscillating circuit. When a conductive object of measurement is approached, the imaginary part of the coil impedance will change primarily. This applies mainly to low operating frequencies, i.e, operating frequencies of up to several 100 kHz. Magnetic objects increase the inductance as they approach the coil, nonmagnetic objects lessen it. Also here, a demodulated output signal is proportional to the distance between the sensor and the object of measurement.
Both in the case of the eddy-current measuring method and in the inductive measuring method, the change in the impedance of a measuring coil arranged in a sensor is measured, when an electrically and/or magnetically conductive object of measurement is approached. The measuring signal thus corresponds to the distance of measurement.
The change in impedance which is create by varying the spacing between the sensor and the object to be measured, thus, results on the one hand from a change in inductance of the coil, and on the other hand from the change in real resistance of the coil. The imaginary part of the coil impedance is thus predetermined, among other things, by the self-capacitance of the measuring coil and, thus, by the entire configuration of the sensor. The electric field lines exiting from the sensor during a measurement, are accordingly also decisive for the self-capacitance of the sensor. When an electrically conductive object of measurement approaches the sensor, the electric field emanating from the sensor is thereby also influenced. This applies likewise, when an object with a relatively high dielectric constant approaches. Consequently, a substance with a hig
REFERENCES:
patent: 4042876 (1977-08-01), Visioli, Jr.
patent: 4053826 (1977-10-01), Wasawa et al.
patent: 4678994 (1987-07-01), Davies
patent: 4956606 (1990-09-01), Kwiatkowski et al.
patent: 5036274 (1991-07-01), Seeburger
patent: 5068607 (1991-11-01), Redlich
Edmonds Warren S.
Micro-Epsilon Messtechnik GmbH & Co. KG
Wieder Kenneth A.
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