WO2015058732A1

WO2015058732A1 - Inductive position sensor using nonlinearly wound coil

Info

Publication number: WO2015058732A1
Application number: PCT/CZ2014/000111
Authority: WO
Inventors: Jan CHLISTOVSKY
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-10-25
Filing date: 2014-10-07
Publication date: 2015-04-30
Anticipated expiration: 2016-04-25
Also published as: CZ2013817A3

Abstract

An inductive position sensor utilizing nonlinearly wound coil comprising two coils, the basic one (L) and the sensing one (LS), where the basic coil (L) is formed of a core and a winding, wherein density and pitch of the winding of the basic coil (L) are nonlinear. Preferably, the core has a conical shape. Also preferably, the core has shape of a ring or an incomplete ring. Also preferably, the winding of the basic coil (L) is formed by a pattern of a printed circuit. Also preferably, the sensing coil (LS) is supplemented by a capacitor C as an oscillating circuit.

Description

Inductive position sensor using nonlinearly wound coi Field of the Art

The invention relates to position sensors, eventually level sensors, on the induction principle.

Prior Art

At present, many models of sensors based on the induction principle are used for position sensing. However, most of them are not able to operate at greater distances, eventually in demanding environments because an open magnetic circuit is used for sensing, where losses increase disproportionately at larger distances.

Further, for completeness, optical sensors are used, which are sensitive to pollution and their production is expensive.

Other sensors are the resistance sensors using a resistive track for the position measuring.

A problem of such sensors is that the resistive track is difficult to seal against entering of dirt, and after a certain number of cycles, the track is worn out, and the accuracy of the sensor decreases thereby.

The float sensors convert the movement of a float on a two-positon level sensor (reed relay). The two-position sensors can be arranged in a row, and we thus obtain stepwise information on the level.

The conductive level sensors indicate the level position reached by passing a current between two electrodes and by galvanically connected levels of a conductive liquid, but they do not detect the non-conductive liquids.

The capacitive sensors operate on the principle of measuring the capacitance of a capacitor whose electrodes are partially submerged in the liquid that forms a dielectric. The level height is variable. Therefore, the dielectric is variable and the overall capacity is changing. The disadvantage is that the accuracy of the measurement depends steeply on the properties of the liquid.

The ultrasonic level sensors operate on the principle of measuring delay of the sent acoustic signal with a frequency above the audible range. Their disadvantage is the sensitivity to any foam or mist eventually present on the ί

material

The radar sensors operate on the same principle as the ultrasonic sensors described above but with a frequency in the order of GHz and they suffer from the same shortcomings.

Summary of the Invention

These disadvantages largely eliminates an inductive position sensor utilizing nonlinearly wound coil comprising two coils, the basic one and the sensing one, where the basic coil is formed of a core and a winding, the substance of which is that density and pitch of the winding of the basic coil are nonlinear.

In a preferred solution the core has a conical shape.

Further, in a preferred solution the core has shape of a ring or an incomplete ring. Further, in a preferred solution the basic coil winding is formed by a pattern of a printed circuit.

Further, in a preferred solution the sensing coil is supplemented by a capacitor as an oscillating circuit.

The here indicated and described inductive position sensor allows a wide range of applications in industry, for example the liquid level detection. The sensor can sense location in the range of the centimetre to meter units with greater accuracy and variability in a measuring system.

Detailed Description of the Drawings

Figure 1 shows an inductive position sensor with a coil formed by a pattern of a printed circuit.

Figure 2 shows an assembly of an inductive position sensor with a coil formed by a pattern of a printed circuit.

Figure 3 shows an inductive position sensor formed as a conical coil.

Figure 4 is an assembly of an inductive position sensor with a conical coil.

Figure 5 is an inductive position sensor formed as a cylindrical coil with modified winding characteristics.

Figure 6 shows an assembly of an inductive position sensor with a cylindrical coil. Figure 7 shows connection of an inductive position ser

measuring electrical losses in a circuit.

Figure 8 shows wiring of an inductive position sensor used as principal wiring for a change of inductance in a coil with short-circuited turns.

Figure 9 shows an inductive position sensor using circuit phase change for sensing. : Figure 10 shows an inductive position sensor used as a variant of the sensor sensing shaft turn.

Figure 11 shows wiring of an inductive position sensor shown as a block diagram with a practical implementation of the sensor with the measurement of the phase. Figure 12 shows wiring of an inductive position sensor as a block diagram with a practical implementation of the sensor.

Figure 13 shows wiring of an inductive position sensor as a block diagram of the sensor using electrical losses in a circuit for determining of the position.

Example of an Embodiment of the Invention

The solution belongs to a large group of passive sensors, when the measured non-electrical quantity is converted by the sensor to a change in inductance, and then it is evaluated in an evaluation circuit.

The substance of the principle and the function (Fig. 6) are that a second coil LS, the so called sensing one, which is significantly narrower and which turns are short- circuited, is slipped over the basic coil L, which is wound so that the density of the turns is higher or the diameter of the coil is larger at one end thereof.

During the mutual displacement of these two coils L, LS, one along the other or one with respect to the other the inductance Lx parameter of this two coil L, LS assembly changes.

This dependence is influenced by the ratio of turns at the beginning and the end of the basic coil L, and further by the course of density of the turns and of its winding. From a change of the inductance Lx it is possible to determine the relative positions of the sensing coil LS with short circuited turns and of the basic coil L.

Further essence of the principle and the function is the variant according to Fig. 9, i.| e. the wiring with a capacitor C in series with the sensing coil LS, whereby a change! in the phase relationships occurs during the physical displacement of the sensing coil LS on the basic coil L, what also allows deducing of the measured position. Other illustrative examples are shown in the attached Figu

Figure 1 shows an inductive position sensor with a coil formed by a pattern of a printed circuit and Figure 2 shows an assembly of an inductive position sensor with a coil formed by a pattern of a printed circuit. Here, a nonlinear pattern of a printed circuit, where the coil is formed by a pattern of a printed circuit, is used for a change in inductance. When the sensing coil LS with short-circuited turns is shifted along the pattern of a printed circuit, different surface area of the turns is influenced in any point of the shifting. Thereby, the inductance is changed.

Figure 3 shows an inductive position sensor designed as a conical coil and Figure 4 shows an assembly of an inductive position sensor with a conical coil, where the conical form of the winding is used to form a non-linearly distributed inductance, and where the whole assembly of the coils L, LS working as a sensor is shown, where the sensing coil LS with the short-circuited turns is shifted along the basic coil L. During their mutual shifting, there is another surface area of the turns in any position of the assembly, whereby inductance is changed.

Figure 5 shows an inductive position sensor designed as a cylindrical coil witha a change in the characteristics of the winding and Figure 6 shows an assembly of an inductive position sensor with this cylindrical coil, where the change in pitch of the winding turns is used to form a nonlinear distribution of the inductance, whereby during the mutual shifting of the coils L, LS there is another surface area of the turns in every position of the assembly, whereby inductance is changed.

Figure 7 shows wiring of an inductive position sensor serving as a sensor used to measure electrical losses in a circuit. It shows a modification of the sensor where electrical losses in a circuit are used for sensing. The more the coils are bound the higher are the losses and it is possible to determine the sensor position.

Figure 8 shows wiring of an inductive position sensor as a principal wiring with a change in inductance having a sensing coil LS with short-circuited turns, it shows the basic wiring of a sensor where change in inductance is used, wherein a coil with short-circuited turns is used.

Figure 9 shows an inductive position sensor to be used to sense a phase change of a circuit. It shows the basic wiring of a sensor used to sense variations in circuit phase, wherein a sensing coil LS connected in series with a capacitor C is used. Figure 10 shows an inductive position sensor as ar

determining turning of a shaft, where the sensing coil LS describes a circle around the shaft axis and the basic coil L is of circular shape.

Figure 11 shows wiring of an inductive position sensor as a block diagram of a real implementation of a sensor measuring the phase. The block diagram describes a real implementation of a sensor. The basis is a basic coil L and a sensing coil LS having a capacitor C in series, which is shifted along the basic coil L and thereby forms a change of the mutual binding of the circuits. The oscillator produces a constant frequency, where in one way is inserted a circuit of the coils L, LS and a capacitor C, and further, the circuit is connected to the block for measuring of the phase angle. The other output of the oscillator is connected to the block for measuring of the phase angle again. The output from the block for measuring of the phase angle is connected to the microprocessor block and then the block provides information of the sensor position.

Figure 12 shows wiring of an inductive position sensor as a block diagram with real implementation of the sensor. The block diagram shows a real implementation of the sensor. The basis is a basic coil L and a sensing coil LS with short-circuited turns, which is shifted along the basic coil L and influences its inductance thereby. The basic coil L is a part of the oscillator, where in case of a change in the inductance of the basic coil L frequency of the oscillator is changed. The oscillator output is counted with a counter and is further evaluated by a microprocessor system, which provides information on the actual position.

Figure 13 shows wiring of an inductive position sensor as a block diagram of this modification of the sensor using measuring of the electrical losses in the circuit for determining of the position.. A block diagram of the modification the sensor using measuring of the electrical losses in the circuit for determining of the position is shown. An oscillator produces cycles of constant frequency and amplitude. A circuit with the basic coii L and the sensing coil LS and a parallel connected resistor R is inserted in the track. The higher the mutual binding of the coils L, LS is, the higher are the losses in the circuit, and the greater is the voltage difference on the input of the comparing circuit. This allows to calculate the mutual position of both coils L, LS in the evaluating circuit. Industrial use

The sensor can sense location in the range of the centimetre to meter units with greater accuracy and variability in a measuring system.

Claims

1. An inductive position sensor utilizing nonlinearly wound coil comprising two coils, the basic one (L) and the sensing one (l_S), where the basic coil (L) is formed of a core and a winding, characterized in that density and pitch of the winding of the basic coi! (L) are nonlinear.

2. The inductive position sensor according to Claim 1 , characterized in that the core has a conical shape.

3. The inductive position sensor according to Claim 1 , characterized in that the core has shape of a ring or an incomplete ring.

4. The inductive position sensor according to Claim 1 , characterized in that the winding of the basic coil (L) is formed by a pattern of a printed circuit.

5. The inductive position sensor according to Claim 1 , characterized in that the sensing coil (LS) is supplemented by a capacitor C as an oscillating circuit.