JP6623518B2 - Distance measuring system and distance measuring method - Google Patents

Description

  The present invention relates to a distance measurement system and a distance measurement method for measuring a distance between a first member and a second member that are relatively movable in a predetermined contact / separation direction.

  2. Description of the Related Art Conventionally, a non-contact type distance meter capable of measuring a distance to a measurement target by magnetism of a permanent magnet is known (see Patent Document 1).

  The range finder described in Patent Literature 1 includes a permanent magnet that generates a magnetic flux passing through a measurement target, a magnetic sensor disposed between the permanent magnet and the measurement target, and a change amount of a distance from the magnetic sensor to the measurement target. And a distance calculation circuit that calculates the distance from the change amount of the magnetic flux density detected by the magnetic sensor. The magnetic sensor includes a core formed in a cylindrical shape, and a detection coil wound on the core.The distance calculation circuit performs a measurement from the magnetic sensor to the measurement target based on the positive and negative peak values of the output voltage at both ends of the detection coil. Calculate the amount of change in distance.

JP-A-3-243801

  In the distance meter described in Patent Literature 1, since the magnetic sensor is disposed between the permanent magnet and the measurement target, there is a large gap between the permanent magnet and the measurement target. For this reason, the magnetic flux passing through the measurement target cannot be increased, and the ratio of the change amount of the magnetic flux density in the magnetic sensor to the change amount of the distance from the magnetic sensor to the measurement target is small. It was difficult to improve the distance accuracy.

  Further, for example, if the size of the permanent magnet is increased, the magnetic flux passing through the object to be measured can be increased, but in this case, the installation space is increased and the cost is increased.

  Therefore, an object of the present invention is to provide a distance measuring system and a distance measuring method capable of improving distance measuring accuracy without increasing the size of a permanent magnet.

  An object of the present invention is to provide a distance measuring system for measuring a distance between a first member and a second member which are relatively movable in a predetermined contact / separation direction for solving the above-mentioned problem. A permanent magnet partially fitted in the formed concave portion, and a magnetic field sensor fixed to the second member and detecting the intensity of a magnetic field generated by the permanent magnet, wherein the first member is formed of a soft magnetic material. The recess is opened toward the second member, the permanent magnet is fixed to the first member by its own magnetic force, and intersects the disengagement direction by fitting into the recess. Provided is a distance measurement system in which movement in a direction is regulated.

  Further, the present invention is directed to a distance measuring method for measuring a distance between a first member and a second member which are relatively movable in a predetermined contact / separation direction for the purpose of solving the above-mentioned problem. A concave portion that opens toward the second member, a permanent magnet is disposed so as to partially fit in the concave portion, and a magnetic field sensor that detects the intensity of a magnetic field generated by the permanent magnet is provided in the second member. Disposed on a member, the first member is made of a soft magnetic material constituting a part of a magnetic path of the permanent magnet, the permanent magnet is fixed to the first member by its own magnetic force, and the concave portion The movement in the direction intersecting the disengagement direction is restricted by the fitting to the first member, and the distance between the first member and the second member is measured based on the strength of the magnetic field detected by the magnetic field sensor. To provide a distance measurement method.

  ADVANTAGE OF THE INVENTION According to the distance measuring system and the distance measuring method which concern on this invention, it becomes possible to improve distance measuring accuracy, without enlarging a permanent magnet.

(A) is an exploded perspective view showing a configuration example of a distance measurement system according to the present embodiment, and (b) is a perspective view showing a magnetic field sensor used in the distance measurement system. FIG. 4 is a cross-sectional view illustrating a peripheral portion of a concave portion of the first member and a permanent magnet fitted and fixed in the concave portion. (A) And (b) is explanatory drawing shown in order to demonstrate operation | movement of a distance measuring system. (A) to (e) show that the fitting ratio of the permanent magnet to the recess is 1.0 (100%), 0.5 (50%), 0.25 (25%), 0.1 (10%). %) And 0 (0%) in each case. 4 is a graph showing a relationship between a distance between a first member 11 and a second member 12 and a strength of a magnetic field detected by a magnetic field sensor.

[Embodiment]
Hereinafter, a distance measuring system according to an embodiment of the present invention and a distance measuring method using the distance measuring system will be described with reference to FIGS.

  FIG. 1A is an exploded perspective view illustrating a configuration example of a distance measurement system according to the present embodiment. FIG. 1B is a perspective view showing a magnetic field sensor used in the distance measuring system.

  The distance measuring system 1 includes a first member 11 and a second member 12 which can relatively move in a predetermined contact / separation direction, and can measure a distance between the first member 11 and the second member 12 in a non-contact manner. It is. In the present embodiment, a case will be described in which the second member 12 is fixed to a fixed member such as a frame (not shown) and the first member 11 is a moving body that moves with respect to the second member 12. Further, the distance measurement system 1 is suitably used, for example, for a short distance measurement for measuring the position of the first member 11 within a range of 20 mm or less from the closest position where the first member 11 comes closest to the second member 12. be able to.

  The distance measurement system 1 includes a permanent magnet 2 partially fitted in a concave portion 110 formed in a first member 11, and a magnetic field sensor fixed to the second member 12 and detecting the intensity of a magnetic field generated by the permanent magnet 2. 3 and a calculation unit (described later) for calculating the distance between the first member 11 and the second member 12 based on the detection result of the magnetic field strength by the magnetic field sensor 3. The distance measuring system 1 is used in an environment where the temperature around the permanent magnet 2 is 100 ° C. or higher. That is, the permanent magnet 2 is arranged in a space where the temperature is 100 ° C. or higher.

  The first member 11 is a moving body whose distance from the second member 12 is to be measured, and moves forward and backward with respect to the second member 12 by receiving a moving force from a moving force generating mechanism (not shown). The first member 11 has a recess 110 formed in a part of the facing surface 11a facing the second member 12 so as to be depressed in a direction perpendicular to the facing surface 11a. In the present embodiment, the internal space of the concave portion 110 has a columnar shape, and opens toward the second member 12.

  The first member 11 is made of a soft magnetic material that forms a part of the magnetic path of the permanent magnet 2. As the soft magnetic material, specifically, an iron-based metal, a martensite-based or a ferrite-based stainless steel can be used.

  In the following description, the case where the first member 11 linearly moves with respect to the second member 12 will be described. However, the present invention is not limited to this, and the first member 11 swings around a support shaft (not shown) (a predetermined angle). (Rotating in a range). In this case, the distance measurement system 1 can measure the distance between the position of the concave portion 110 that changes with the swing of the first member 11 and the second member 12.

  The permanent magnet 2 is a samarium cobalt magnet or a neodymium magnet. The samarium-cobalt magnet is also referred to as a samarium magnet and is a rare-earth magnet containing samarium (Sm) and cobalt (Co) as main components. The neodymium magnet is a rare earth magnet mainly containing neodymium (Nd), iron (Fe), and boron (B). The samarium cobalt magnet and the neodymium magnet can obtain a higher residual magnetic flux density than, for example, a ferrite magnet. In the present embodiment, the residual magnetic flux density of the permanent magnet 2 is 1.0 T (tesla) or more. In addition, nickel or the like may be plated on the surface of these magnets for rust prevention or the like.

  In the present embodiment, the permanent magnet 2 has a columnar shape, and a pair of magnetic poles (N pole and S pole) are formed side by side in the direction of the central axis c. One end 21 of the permanent magnet 2 in the direction of the center axis c along the direction in which the pair of magnetic poles are arranged is fitted into the recess 110 of the first member 11. The end face 2 b of the permanent magnet 2 at the other end 22 opposite to the one end 21 faces the second member 12.

  In the present embodiment, the second member 12 is made of a molding resin, and the magnetic field sensor 3 is insert-molded in the molding resin. In the present embodiment, the second member 12 has a quadrangular prism shape. However, the second member 12 may be any non-magnetic material that can fix the magnetic field sensor 3, and its material and shape are various. Can be used.

  In the present embodiment, the magnetic field sensor 3 is a Hall IC, and a main body 30 in which a Hall element for converting the intensity of a magnetic field into an electric signal using the Hall effect is sealed with an insulator such as resin or ceramic. , And first to third lead wires 31 to 33 derived from the main body 30. The first lead 31 is a power supply line, the second lead 32 is a signal line, and the third lead 33 is a ground line. The main body 30 is arranged in a position and a direction in which the strength of the magnetic field along the central axis c of the permanent magnet 2 can be detected. The magnetic field sensor 3 outputs an electric signal from the second lead wire 32 according to the strength of the magnetic field.

  FIG. 2 is a cross-sectional view showing the periphery of the concave portion 110 of the first member 11 and the permanent magnet 2 in which one end 21 is fitted and fixed to the concave portion 110 in a cross section including the central axis c.

  The end surface 2 a of the one end 21 of the permanent magnet 2 is in surface contact with the bottom surface 110 a of the recess 110. The permanent magnet 2 is fixed to the first member 11 by its own magnetic force. That is, the permanent magnet 2 is fixed to the first member 11 by the attraction force of the permanent magnet 2 itself without using fixing means such as an adhesive.

  Further, the movement of the permanent magnet 2 in the direction intersecting with the direction of separation and contact with the second member 12 is restricted by fitting into the recess 110. In FIG. 2, the direction of contact and separation is indicated by an arrow A. In the present embodiment, this direction of contact is parallel to the central axis c of the permanent magnet 2.

As shown in FIG. 2, assuming that the diameter of the permanent magnet 2 is D ₁ and the inside diameter of the recess 110 of the first member 11 is D ₂ , the inside diameter D _{2 of the} recess 110 is slightly smaller than the diameter D ₁ of the permanent magnet 2. The diameter difference ΔD (ΔD = D ₂ −D ₁ ) is, for example, 0.5 mm. The depth of the recess 110, i.e. the fitting depth of the permanent magnet 2 in the recess 110 when the _{D 3,} the depth _{D 3} is deeper than the diameter difference [Delta] D. That is, the diameter D ₁ of the permanent magnet 2, the inner diameter D _{2 of} the recess 110, and the fitting depth D ₃ of the permanent magnet 2 in the recess 110 satisfy the following relational expression (1).
D ₂ −D ₁ <D ₃ (1)
Thereby, even when vibration or impact is applied to the first member 11, the permanent magnet 2 is prevented from detaching from the recess 110.

Incidentally, the fitting depth _{D 3} of the permanent magnet 2 in the recess 110 is desirably 0.5mm or more. When the fitting depth _{D 3} is less than 0.5 mm, for example, when a vibration or shock is applied to the first member 11, over the side surface 110b of the recess 110 the permanent magnet 2, the positional deviation of the permanent magnet 2 This is because it easily occurs.

Furthermore, when the thickness of the central axis c direction of the permanent magnet 2 and t, the thickness t is smaller than the diameter D ₁ of the permanent magnet 2 (t <D _1). That is, the permanent magnet 2 is formed in a flat cylindrical shape. As a result, the end face 2 a at the one end 21 of the permanent magnet 2 is smaller than the bottom face 110 a of the recess 110 as compared with the case where the thickness t of the permanent magnet 2 in the direction of the central axis c is larger than the diameter D _{1 of} the permanent magnet 2. The inclination and the falling of the permanent magnet 2 are suppressed.

The ratio of the length (fitting depth D ₃ ) of the portion fitted to the concave portion 110 to the total length (thickness t) of the permanent magnet 2 in the direction of the central axis c is defined as a fitting ratio R (R = D ₃ / t). Then, the fitting ratio R is desirably 0.1 to 0.5. That is, in the present embodiment, the ratio of the length of the portion fitted to the concave portion 110 to the entire length of the permanent magnet 2 in the direction of the central axis c is 10 to 50% (10% or more and 50% or less). If this ratio is less than 10%, the permanent magnet 2 tends to slip out of the recess 110, which is not preferable. On the other hand, if this ratio exceeds 50%, the magnetic field of the permanent magnet 2 becomes difficult to reach the magnetic field sensor 3, which is not preferable.

In FIG. 2, the thickness t of the permanent magnet 2 is 3 mm, fitting depth _{D 3} is 0.75 mm, it is illustrated for the case the fitting ratio R is 0.25 (25%).

FIGS. 3A and 3B are explanatory diagrams illustrating the operation of the distance measurement system 1. FIG. In FIG. 3B, the distance L ₂ between the first member 11 and the second member 12 is equal to the distance L ₁ between the first member 11 and the second member 12 in the state shown in FIG. It shows a smaller state.

  3A and 3B, the magnetic field sensor 3 inside the second member 12 and the cable 4 connected to the magnetic field sensor 3 are indicated by solid lines, and two lines of magnetic force indicating the magnetic field of the permanent magnet 2 are shown. This is indicated by a chain line. The magnetic field sensor 3 is connected to the calculation unit 5 by a cable 4.

  The permanent magnet 2 has an S pole at one end 21 and an N pole at the other end 22. The lines of magnetic force radiated from the end face 2b at the other end 22 are curved and enter the first member 11. Further, a part of the magnetic force lines emitted from the end face 2 a at the one end 21 is linked to the main body 30 of the magnetic field sensor 3.

  The cable 4 includes first to third electric wires 41 to 43 and a sheath 40 for covering the first to third electric wires 41 to 43 collectively. The first to third electric wires 41 to 43 are insulated electric wires each having a core wire insulated and coated. The core wire of the first electric wire 41 is connected to the first lead wire 31 of the magnetic field sensor 3 and the second electric wire is connected to the first electric wire 41. The core of 42 is connected to the second lead 32 of the magnetic field sensor 3, and the core of the third electric wire 43 is connected to the third lead 33 of the magnetic sensor 3.

  When the first member 11 approaches the second member 12, the intensity of the magnetic field detected by the magnetic field sensor 3 increases, and when the first member 11 separates from the second member 12, the intensity of the magnetic field detected by the magnetic field sensor 3 increases. Becomes weaker. The calculation unit 5 calculates the distance between the first member 11 and the second member 12 by calculation based on the strength of the magnetic field detected by the magnetic field sensor 3.

  The arithmetic unit 5 converts the output signal of the magnetic field sensor 3 transmitted by the second electric wire 42 of the cable 4 from analog to digital, for example, a CPU (Central Processing Unit), a storage element such as a ROM or a RAM, and the like. The storage element stores relationship information indicating the relationship between the strength of the magnetic field detected by the magnetic field sensor 3 and the distance between the first member 11 and the second member 12. It is remembered. The CPU refers to the relation information stored in the storage element based on the numerical information indicating the strength of the magnetic field detected by the magnetic field sensor 3 and digitally converted by the AD conversion element, and determines the relationship between the first member 11 and the second member 12. Is obtained by calculation.

(Consideration of fitting ratio R of permanent magnet 2)
Next, a preferred range of the fitting ratio R, which is a ratio of the length (fitting depth D ₃ ) of the portion fitted to the concave portion 110 to the total length (thickness t) of the permanent magnet 2 in the direction of the central axis c, This will be described with reference to FIGS.

  FIGS. 4A to 4E show that the fitting ratio R is 1.0 (100%), 0.5 (50%), 0.25 (25%), 0.1 (10%), FIG. 5 is a schematic diagram schematically showing lines of magnetic force radiated from the permanent magnet 2 in each case of FIG. 5 and 0 (0%). FIG. 5 is a diagram showing the distance between the first member 11 and the second member 12 in each case. 6 is a graph showing a relationship between L and a magnetic field intensity B detected by the magnetic field sensor 3. 4A to 4E, the distance between the end surface 2b on the N pole side of the permanent magnet 2 and the second member 12 in the direction along the central axis c of the permanent magnet 2 is constant.

  As shown in FIGS. 4A to 4E, as the fitting ratio R is smaller, the lines of magnetic force radiated from the permanent magnet 2 extend significantly along the central axis c of the permanent magnet 2 and are detected by the magnetic field sensor 3. The magnetic field strength increases. Further, the distance between the first member 11 and the second member 12 can be determined with higher accuracy as the change in the strength of the magnetic field detected by the magnetic field sensor 3 accompanying the movement of the first member 11 increases. That is, as is clear from FIG. 5, the smaller the fitting ratio R, the larger the magnetic field intensity B detected by the magnetic field sensor 3 according to the change in the distance L between the first member 11 and the second member 12. Therefore, the detection accuracy of the distance L between the first member 11 and the second member 12 can be increased.

However, when the permanent magnet 2 is not fitted in the recess 110, i.e. the fitting depth D ₃ is zero, the positional deviation of the permanent magnet 2 is generated by the permanent magnet 2 slides relative to the first member 11 As a result, the distance between the first member 11 and the second member 12 cannot be measured accurately. Further, even if the permanent magnet 2 is fitted in the recess 110, if the fitting ratio R is too small, the permanent magnet 2 tends to fall. Therefore, in the present embodiment, by setting the fitting ratio R to be 0.1 to 0.5 (10 to 50%), it is possible to prevent the displacement and the fall of the permanent magnet 2 and to prevent the permanent magnet 2 from falling. This is to improve the measurement accuracy of the distance to the member 12.

(Operation and Effect of Embodiment)
According to the embodiment described above, the following operations and effects can be obtained.

(1) Since the permanent magnet 2 is fixed to the first member 11 to be measured and moves with respect to the second member 12 together with the first member 11, the strength of the magnetic field intensity that changes with the movement of the first member 11 The change can be directly detected by the magnetic field sensor 3 fixed to the second member 12. Thereby, the amount of change in the magnetic field intensity detected by the magnetic field sensor 3 accompanying the movement of the first member 11 can be increased, and the measurement accuracy of the distance between the first member 11 and the second member 12 can be improved. Becomes possible.

(2) Since the permanent magnet 2 is fixed to the first member 11 by its own magnetic force, the permanent magnet 2 can be fixed without providing fixing means such as an adhesive. Accordingly, the number of steps for attaching the permanent magnet 2 to the first member 11 can be reduced, and even in a high temperature environment exceeding, for example, 100 ° C., the permanent magnet 2 can be mounted without concern about a decrease in the adhesive strength of the adhesive. 2 can be stably fixed to the first member 11.

(3) Since the permanent magnet 2 is fitted into the concave portion 110 of the first member 11, it is possible to prevent the position shift and the falling of the permanent magnet 2 with respect to the first member 11.

(4) The fitting ratio R, which is the ratio of the length (fitting depth D ₃ ) of the portion fitted to the recess 110 to the total length (thickness t) of the permanent magnet 2 in the direction of the central axis c, is 0.1 to 0. .5 (10 to 50%), it is possible to achieve both the prevention of the displacement and the fall of the permanent magnet 2 and the improvement of the measurement accuracy of the distance between the first member 11 and the second member 12.

(5) By using a samarium-cobalt magnet or a neodymium magnet as the permanent magnet 2, a higher attraction force can be obtained as compared with a case where the permanent magnet 2 is a ferrite magnet, and the first member 11 receives vibration or impact. However, it is possible to suppress the permanent magnet 2 from being inclined or detached from the first member 11.

(6) By setting the residual magnetic flux density of the permanent magnet 2 to 1.0 T or more, it is possible to more reliably fix the permanent magnet 2 to the first member 11.

(Summary of Embodiment)
Next, technical ideas grasped from the embodiments described above will be described with reference to the reference numerals and the like in the embodiments. However, each reference sign in the following description does not limit the constituent elements in the claims to members specifically shown in the embodiments.

[1] A distance measuring system (1) for measuring a distance between a first member (11) and a second member (12) relatively movable in a predetermined contact / separation direction, wherein the first member (11) A permanent magnet (2) partially fitted in the formed recess (110); and a magnetic field sensor (2) fixed to the second member (12) and detecting the intensity of a magnetic field generated by the permanent magnet (2). 3), wherein the first member (11) is made of a soft magnetic material, the recess (110) opens toward the second member (12), and the permanent magnet (2) is The distance measuring system (1), which is fixed to the first member (11) by the magnetic force of (1), and is restricted from moving in a direction intersecting with the direction of separation by fitting into the recess (110).

[2] One end (21) of the permanent magnet (2) in the direction of the center axis (C) along the arrangement direction of the pair of magnetic poles is fitted into the recess (110), and the center of the permanent magnet (2) is formed. The distance measuring system (1) according to [1], wherein a ratio of a length of the portion fitted to the concave portion (110) to an entire length in the direction of the axis (C) is 10 to 50%.

[3] the permanent magnet (2) and the recess (110) are both cylindrical, the diameter of the permanent magnet (2) and _{D 1,} the inner diameter of the recess (110) and _{D 2,} the recess ( when the fitting depth of the permanent magnets (2) in 110) was _{D 3,} satisfy the following formula, the distance measuring system according to [1] or [2] (1). D ₂ −D ₁ <D ₃

[4] The distance measurement system (1) according to any one of [1] to [3], wherein the permanent magnet (2) is a samarium cobalt magnet or a neodymium magnet.

[5] The distance measurement system (1) according to any one of [1] to [4], wherein a residual magnetic flux density of the permanent magnet (2) is 1.0 T or more.

[6] The distance measurement system (1) according to any one of [1] to [5], wherein the permanent magnet (2) is arranged in a space where the temperature is 100 ° C or higher.

[7] A distance measuring method for measuring a distance between a first member (11) and a second member (12) relatively movable in a predetermined contact / separation direction, wherein the first member (11) is provided with the second member. A recess (110) that opens toward the member (12) is formed, and a permanent magnet (2) is arranged so that a part thereof is fitted into the recess (110), and a magnetic field generated by the permanent magnet (2) A magnetic field sensor (3) for detecting the intensity of the magnetic field is disposed on the second member (12), and the first member (11) is formed of a soft magnetic material forming a part of a magnetic path of the permanent magnet (2). The permanent magnet (2) is fixed to the first member (11) by its own magnetic force, and moves in a direction intersecting with the separation / contact direction by fitting into the concave portion (110). Is regulated, based on the strength of the magnetic field detected by the magnetic field sensor (3). The distance between the first member (11) and said second member (12) is measured, the distance measuring method.

  The embodiments of the present invention have been described above, but the embodiments described above do not limit the invention according to the claims. Also, it should be noted that not all combinations of the features described in the embodiments are necessarily essential for solving the problem of the invention.

  In addition, the present invention can be appropriately modified and implemented without departing from the spirit thereof. For example, in the above embodiment, the case where the second member 12 is fixed and the first member 11 moves with respect to the second member 12 has been described. The distance measurement system may be configured such that the second member 12 moves with respect to the first member 11 while being fixed to the fixing member.

DESCRIPTION OF SYMBOLS 1 ... Distance measuring system 11 ... First member 110 ... Recess 12 ... Second member 2 ... Permanent magnet 3 ... Magnetic field sensor

Claims (5)

A distance measuring system that measures a distance between a first member and a second member that are relatively movable in a predetermined contact / separation direction,
A permanent magnet that partially fits into the recess formed in the first member and is disposed in a space where the temperature is 100 ° C. or higher;
A magnetic field sensor fixed to the second member and detecting the intensity of a magnetic field generated by the permanent magnet,
The first member is made of a soft magnetic material, and the concave portion opens toward the second member,
The permanent magnet is fitted so that an end surface at one end in a central axis direction along a direction in which the pair of magnetic poles are arranged is in surface contact with the bottom surface of the concave portion, and the second magnet is formed only by its own magnetic force without using an adhesive. Is fixed to one member, and movement in a direction intersecting with the contact / separation direction is restricted by fitting into the concave portion ,
The ratio of the length of the portion fitted into the concave portion to the total length of the permanent magnet in the central axis direction is 10 to 50%.
Distance measurement system. The permanent magnet and the recess are both cylindrical,
The diameter of the permanent magnet and D _1, the inner diameter of the recess and D _2, when the fitting depth of the permanent magnets in the concave portion was set to D _3, satisfy the following formula,
The distance measuring system according to claim 1 .
D ₂ −D ₁ <D ₃ The permanent magnet is a samarium cobalt magnet or a neodymium magnet,
The distance measuring system according to claim 1 . The permanent magnet has a residual magnetic flux density of 1.0 T or more;
The distance measuring system according to claim 1 . A distance measuring method for measuring a distance between a first member and a second member relatively movable in a predetermined contact / separation direction,
Forming a recess in the first member that opens toward the second member;
Along with a part fitted into the recess, a permanent magnet is arranged in a space where the temperature is 100 ° C. or higher,
A magnetic field sensor for detecting the intensity of the magnetic field generated by the permanent magnet is disposed on the second member,
The first member is made of a soft magnetic material constituting a part of a magnetic path of the permanent magnet,
The permanent magnet is fitted so that an end surface at one end in a central axis direction along a direction in which the pair of magnetic poles are arranged is in surface contact with the bottom surface of the concave portion, and the second magnet is formed only by its own magnetic force without using an adhesive. Is fixed to one member, and movement in a direction intersecting with the contact / separation direction is restricted by fitting into the concave portion,
A ratio of a length of the portion fitted to the concave portion to a total length of the permanent magnet in a central axis direction is 10 to 50%,
Measuring the distance between the first member and the second member based on the strength of the magnetic field detected by the magnetic field sensor,
Distance measurement method.

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