RU2454625C1 - Inductive position sensor - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: inductive position sensor has a fixed part and a movable part adapted to move relative the fixed part with one degree of freedom. The fixed and movable parts of the sensor are made from insulating material and face each other by sides on which there are printed zigzag-like rectangular inductance coils, respectively with passive short and active long conductor strips which are mutually parallel and lie with equal spacing. The movable part of the sensor is adapted to move relative the fixed part along the active long conductors of the zigzag-like rectangular coils. The fixed part of the inductive position sensor can have two identical coils placed along the direction of displacement of the movable part with a coil which is in the initial state at the centre between the fixed coils.

EFFECT: wider measurement range, simple design of the sensor, high accuracy of measuring linear displacements.

2 cl, 9 dwg

Description

The invention relates to measuring technique and can be used to measure linear displacements using an induction type displacement transducer.

Known "Non-contact position sensor with mutual inductance" according to the patent of France: FR 2830614 A1 dated 04/11/2003, IPC G01D 5/22 - [1], containing printed rectangular windings on plates of dielectric material, next to the windings are plates of material with high magnetic permeability and ferromagnetic pads, between which there is a moving magnet, the position of which is determined by the perturbation of the electromagnetic field between the ferromagnetic pads.

A disadvantage of the known invention is that the printed windings are connected through a magnetic circuit, the magnetic permeability of the material of which is very dependent on temperature, which requires complicating the design of the sensor by introducing temperature compensation. In addition, the presence of a magnetic circuit allows you to use only a low range of operating frequencies, which also reduces the accuracy of the measurement.

Known "Induction Converter linear displacements" by A. with. USSR No. 1516751 of 10.23.1989, IPC G01B 7/00 - [2], containing movable and fixed parts of dielectric material in the form of coaxial tubes and longitudinal sections and printed zigzag rectangular windings, the active conductors of which are mutually parallel and are located at the same pitch.

Also known "Position Sensor" according to US patent US 2942212 from 06/21/1960, Cl. 336-30 - [3], containing the movable and stationary parts of the dielectric material with printed zigzag rectangular windings, the active conductors of which are mutually parallel and are located at the same pitch.

The direction of movement of the moving part is relatively motionless in analogues [2] and [3] is perpendicular to the active long conductors of zigzag rectangular coils. This movement of the coils relative to each other significantly complicates the processing of signals from the sensor, reduces its reliability and increases the cost of production.

The prototype of the proposed technical solution is “Inductive measuring coil” according to USSR author's certificate No. 1552240 dated 03/23/1990, IPC H01F 15/14, G01B 7/00 - [4] containing a fixed dielectric base with a zigzag winding placed on its surface in in the form of identical quadrangular open cells distributed on the base surface and a movable part in the form of an armature, which can be made of a dielectric - measures the capacitance of a winding, an electrical conductor - measures the quality factor of windings Or ferromagnetic - measures the winding inductance.

The disadvantage of the prototype [4] is the implementation of a complex geometric channel in the dielectric layer, laying the conductor of the winding in it and securing it, which significantly complicates the production technology and its cost. In addition, the testimony of the prototype is highly dependent on the temperature at which it is operated.

Based on the above disadvantages of analogues and prototype, there are tasks to expand the measurement range, simplify the design of the sensor and improve the accuracy of measurement of linear displacements.

The problem is solved in that

an induction position sensor comprising a fixed part and a movable part mounted to move relative to the fixed part with one degree of freedom, the fixed and movable parts of the sensor are made of dielectric material, facing each other with printed zigzag rectangular inductor coils applied to them, respectively, with passive short and active long printed conductors, which are mutually parallel and spaced at the same pitch, while zhnaya portion movably mounted relative to the stationary portion along the active length of the conductor zigzag rectangular coils. The fixed part of the induction position sensor may contain two identical coils mounted along the direction of movement of the moving part with the coil, which is in this initial position centered between the fixed coils of the fixed part.

The introduction of the distinguishing feature: "the movable part is mounted with the possibility of moving relatively stationary part along the active long conductors of zigzag rectangular coils" is necessary to significantly expand the measurement range, as well as to simplify the design of the sensor. This movement of the coils relative to each other greatly simplifies the processing of signals from the sensor and allows you to increase the operating frequency of the sensor and, therefore, increase its accuracy.

The coils made on the fixed and moving parts of the coil according to the technology of printed circuit boards contain a thin layer of metal on which the properties of the substrate of the printed circuit board are imposed. And the substrate - a plate made of a composite material, as is known, has low coefficients of linear and volumetric thermal expansion, which ensures stability of measurements in wide temperature ranges.

The introduction of the distinguishing feature: "the fixed part of the induction position sensor contains two identical coils mounted along the direction of movement of the moving part with the coil, which is in this initial state centered between the fixed coils of the fixed part" is necessary to improve the accuracy of linear displacement measurements by the claimed inductive displacement sensor . In addition, the temperature stability of the sensor is significantly increased due to the difference signal from two fixed coils, which are identical in temperature characteristics.

According to the second paragraph of the formula of the claimed technical solution, it is known to perform “Schemes with a linearly adjustable differential transformer LVDT as a displacement sensor or a force sensor and a method for using such a circuit” according to German patent No. 10313021 B3 dated 02.09.2004, IPC G01B 7/02 - [5 ], with one primary winding and two secondary windings, the outputs of which through respectively two integrators are connected to the adder, the output of which is connected to the connector of an external electrical device.

However, in the known analogue [5] and in the claimed technical solution, there are significant differences. So, in the analogue [5] from the master oscillator, “triangular” signals (pulses) with adjustable leading and trailing edges are supplied to the primary winding, and in the claimed technical solution, the sinusoidal signals are fed from the master oscillator to the primary winding, and there is no core between the coils, which allows you to increase the operating frequency and the corresponding sensitivity of the induction sensor.

Figure 1 shows the fixed and movable parts of the induction displacement sensor made of a dielectric material, with printed zigzag rectangular inductors printed on them (view of the coils). Figure 2 is a view of the stationary and moving parts of the induction displacement sensor in operating condition (the fixed and moving parts of the induction displacement sensor are facing each other by coils). Figure 3 - the stationary part of the sensor with two coils and the moving part of the sensor with one coil (view of the coils). In Fig.4 is a view of the stationary and moving parts of the sensor of Fig.3 in the working state (the fixed and moving parts of the induction displacement sensor are facing each other by coils). In Fig.5 is a view of the induction displacement sensor of Fig.3 and Fig.4, installed in the device for testing the sensor. 6 is an equivalent circuit of an induction displacement sensor from one fixed and one moving coils. In Fig.7 is a schematic diagram for ensuring the operability of the sensor of Fig.6. On Fig - equivalent circuit induction displacement sensor from two fixed and one moving coil. In Fig.9 - circuitry for ensuring the operability of the sensor of Fig.8.

The induction position sensor contains a fixed 1 and a movable 2 parts with the ability to move the movable 2 parts relative to the fixed 1 part with one degree of freedom. The fixed 1 and moving 2 parts of the sensor are made of dielectric material and face each other with printed zigzag rectangular inductors, 3 and 4, respectively, with passive short and active long printed conductors, which are mutually parallel and arranged at the same pitch. In this case, the movable part 2 is installed with the possibility of moving relatively stationary 1 part along the active long conductors of the zigzag rectangular coils 3 and 4. In other words, the direction of movement of the movable part 2 relative to the stationary 1 is parallel to the active long conductors of the zigzag rectangular coils 3 and 4. The fixed part of the induction sensor the position may contain two identical coils 3 and 5 installed along the direction of movement of the movable part 2 with the coil 4, which while it is located in the initial state in the center between the fixed coils 3 and 5 of the fixed part 1. The device for testing the induction displacement sensor with two fixed (3 and 5) and one movable coil 4 contains a base 6 and a movable carriage 7, coils 3 and 5 connected to the signal processing device by fixed wires 8, and the coil 4 - flexible wires 9.

To explain the operation of the induction displacement sensor, equivalent circuits in the form of a transformer - Fig.6 or differential transformer - Fig.8, with a linearly varying coupling coefficient between the coils can be applied. To ensure the operability of inductive displacement sensors according to the structural diagrams of Fig.6 and Fig.8 can be used typical circuit solutions presented respectively in Fig.7 and Fig.9.

In Fig.7: G is a generator of a sinusoidal power signal of the coil 4 of the movable part 2; PD - peak detector; U - large-scale amplifier; Uout - analog output signal from coil 3, proportional to the movement of the moving part 2 with coil 4.

In Fig.9: G is a generator of a sinusoidal power signal of the coil 4 of the movable part 2; PD1 - peak detector coil 3 of the fixed part 1; PD2 - peak detector coil 5 of the fixed part 1; Y - amplifier scale differential signal; Uout - analog output signal proportional to the movement of the moving part 2 with the coil 4.

Actually for operating frequencies of the order of 2 MHz in the dimensions of the movable 2 parts 42 × 22 mm and the stationary 1 part 84 × 22 mm, the pitch of the conductors of coils 4, 3 and 5, equal to 0.8 mm, with a width of conductors of 0.5 mm and an air gap between the movable and fixed part of 0.2 mm, the working area for moving the movable part 2 is 30 mm The range of the output signal in this case is ± 2 V with a conversion error not worse than ± 0.5%.

Modern technology of printed circuit boards allows the manufacture of printed coils with a high degree of accuracy, in this regard, if it is necessary to obtain a higher conversion accuracy, the requirements for the pitch and width of the conductors, as well as the air gap between the coils, can be more stringent.

As can be seen from the above, it is most advisable to use such an induction displacement sensor in the deformation control systems of various objects.

We believe that the proposed induction position sensor has all the criteria of the invention, since the combination with the restrictive and distinctive features of the claims according to claim 1 and claim 2 is new for the construction of induction position sensors and, therefore, meets the criterion of "novelty."

The set of features of the claims of the proposed device is unknown at this level of technology and does not follow the well-known rules for the development and construction of induction position sensors, which proves compliance with the criterion of "inventive step".

The development, construction and implementation of the proposed induction position sensor does not present any structural, technical and technological difficulties, from which the criterion “industrial applicability” follows.

Literature

1. French patent: FR 2830614 A1 dated 04/11/2003, IPC G01D 5/22 - “Non-contact position sensor with mutual inductance”.

2. USSR copyright certificate No. A.S. USSR No. 1516751 of 10.23.1989, IPC G01B 7/00 - “Induction converter of linear displacements”.

3. US patent US 2942212 from 06.21.1960, Cl. 336-30 - "Position Sensor".

4. USSR author's certificate No. 1552240 dated 03/23/1990, IPC H01F 15/14, G01B 7/00 - “Inductive measuring transducer coil” - prototype.

5. German patent No. 10313021 B3 dated 02.09.2004, IPC G01B 7/02 - “Scheme with linearly adjustable differential transformer LVDT as a displacement sensor or force sensor and how to use such a scheme”.

Claims (2)

1. An induction position sensor comprising a fixed part and a movable part mounted to move relative to the fixed part with one degree of freedom, the fixed and movable parts of the sensor made of dielectric material, facing each other with printed zigzag rectangular inductor coils applied to them , respectively, with passive short and active long printed conductors that are mutually parallel and spaced at the same pitch, different schiysya in that the movable part is movable relative to the stationary portion along the active length of the conductor zigzag rectangular coils. 2. The induction position sensor according to claim 1, characterized in that the fixed part of the induction position sensor contains two identical coils mounted along the direction of movement of the moving part with the coil, which is in this initial state centered between the fixed coils of the fixed part.

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