SU1645808A1 - Non-contact inductive transducer of distance till ferromagnetic object surface - Google Patents

Description

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(21) 4602992/28

(22) 11/09/88

(46) 04.30.91. Bul Number 16

(71) Institute of problems of reliability and durability of machines of the Academy of Sciences of the BSSR

(72) I.A. Vasilets, Yu.V. Skorynin, W.K. Nasledyshev and I.I. Uzunova (33) 531.717 (088.8)

(56) USSR author's certificate I 1420344 ,. cl. G 01 B 7/00, 1986.

(54) NONCONTACT INDUCTIVE-DISTANCE SENSOR TO OBJECT SURFACE (57) The invention relates to a measurement technique and is aimed at reducing the dimensions and increasing the sensitivity of an inductive distance sensor to the surface of a ferromagnetic object. The sensor contains a glass-like housing 1 made of a ferromagnetic material, inside which

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it is fixed with a protruding diameter of compensa tion. This would be made from permallosed sections of the central one. When the current is switched on, the magnetic object is 6 distances away and the measurement is cut off and the signal is measured.

a cylindrical core 3 is fixed with a protrusion in the central part of a larger diameter than its edge portions, which are located on the measuring and compensation coils of 4.5 inductances. The core 3 and the body 1 can be made of high nickel permallo. The core is made with a certain ratio of the length of the edge sections of the core to the diameter of its central part, equal to 0.8-0.9. When the sensor is turned on in the AC circuit, a magnetic field is generated around the coils, affecting the control object 6. Depending on the distance of the sensor to the control object 6, the inductive resistance of the coil 4 changes, which leads to the imbalance of the measuring-bridge circuit, the output signal of which is proportional to the measured distance. 1 il.

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The invention relates to a measuring technique and can be used to measure the distance to the surface of an object made of a ferromagnetic material.

The purpose of the invention is to reduce the size and increase the sensitivity of an inductive sensor due to the appropriate choice of the dimensions of its structural elements.

The drawing schematically shows the design of a contactless inductive distance sensor to the object surface.

The sensor contains a glass-like ferromagnetic body 1, in which a cylindrical ferromagnetic core 3 is fixed with the help of a holder 2, which has a cruciform shape in its longitudinal section due to the protrusion in its central part exceeding the diameter of its edge sections.

The rta edge areas of the core 3 are placed measuring and compensating coils A and 5 with inductances with the same number of turns included, for example, in a bridge circuit (not shown) for measuring the ratio of their inductances or inductances that depend on the distance; these coils to the surface of the ferromagnetic object 6 and to the bottom of the glass-like body, respectively. The ratio of the length 1 of the edge portions to the diameter d of the core 3 in its central part is selected from the ratio 0.8-0.9. This ratio is

It has been experimentally obtained and has a limiting ferromagnetic glass-encapsulation on top for reasons of preventing the growth of the overall dimensions of the sensor. The lower limit of this ratio is limited by a technologic and retractable housing, a cylindrical core, longitudinally cruciform in its cross section, having a protrusion of a larger diameter in its central part.

It is possible to wind the coils in reduced dimensions to obtain a given sensitivity and an increase in the nonlinearity of the calibration characteristic. The internal volume of the sensor housing can be sealed, for example, filled with compound 7 on an epoxy base.

Inductive sensor works as follows.

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When the sensor is switched on in the AC circuit (bridge), an alternating electromagnetic field is generated around the measuring and compensation coils 4 and 5 of the inductor. When the sensor approaches the ferromagnetic measurement object 6, the sensor core 3 and this object form a magnetic circuit with an air gap, which changes when the inductive resistance of the measuring inductance coil 4 changes, which leads to unbalancing of the bridge and producing a signal proportional to the displacement object.

An increase in the sensitivity of the sensor of this design is achieved due to the redistribution of the magnetic flux with an increase in its concentration in the control surface zone, due to an increase in the diameter of the core 3 in its middle part relative to the diameter of the identical end parts of the core adjacent to it and the ratio of their length to the diameter of the average parts within no more than 0.8, 9.

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The sensor is characterized by an increased sensitivity to the change in the distance to the object's surface and allows monitoring surfaces of different curvature without re-calibration of the sensor.

Claims (1)

Invention Formula Contactless inductive distance sensor to the object surface, containing a ferromagnetic stakanoobrazny case, fixed therein a cylindrical core, longitudinally cruciform in longitudinal section, having in its central part a protrusion of a larger diameter what is the diameter placed its marginal areas these areas meters, measure and compensate inductors, characterized in that, in order to reduce the dimensions and increase the sensitivity, the ratio of the length of the edge sections of the core to the diameter of its central part is chosen in the range of 0.8U, U.