JPH0817311A - Two-wire type magnetic switch circuit using hall element - Google Patents

Abstract

PURPOSE:To propose reform for improving the temperature property with high sensitivity, in a two-wire type magnetic switch circuit using a Hall element driven with a constant current. CONSTITUTION:A Hall element 1 is driven with a constant current by a constant current source 2. A first resistor R1 is connected between the output terminals 1a and b of the Hall element and the input terminals 3a and 3b of a differential amplifier 3. One side of a second resistor R2 is connected between the input terminal 3a and the output terminal 4, and the other side to the output terminal 3b. The first and second resistors R1 and R2 are connected so that the temperature variation of the output voltage appearing in the output terminal 4 may reach the specified value or under.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a device using a hall element.
The present invention relates to a wire type magnetic switch circuit, and more particularly to an improvement for temperature compensation thereof.

[0002]

2. Description of the Related Art Hall elements are magnetoelectric conversion elements that utilize the Hall effect, and are widely used as various magnetic sensors such as position detection and rotation detection for small precision brushless motors and magnetic switches. This Hall effect will be described with reference to FIG. 14. A Hall element H having a thickness d and made of an appropriate semiconductor.
The input terminals I ₁ and I ₂ and the output terminals O ₁ and O ₂ are attached to the sensing section of the power source, the input control voltage Ic is supplied from the power source Os between the input terminals I ₁ and I ₂ , and the magnetic field 7 having the magnetic flux density B is externally applied. Is applied perpendicularly to the surface of the sensing portion, a potential difference (Hall voltage) V _H is generated between the output terminals O ₁ and O ₂ , which can be expressed by the following equation. _VH = _RH / d * Ic * B ( _RH is a Hall coefficient) There are two types of driving methods for this Hall element: a constant current driving method and a constant voltage driving method. In the case of the constant current drive method, the Hall voltage V _H is represented by the above equation, a constant current is supplied as the control current Ic, and the temperature characteristic of V _H depends on the temperature characteristic of R _H. Further, in the case of the constant voltage driving method, the Hall voltage V _H is represented by V _H = μ _H · W / I · Vin · B. μ _H is the electron mobility in the semiconductor, and the temperature characteristic of V _H depends on the temperature coefficient of μ _H. W is the width of the sensitive portion, and I is the length of the sensitive portion.

[0003]

In order to realize a two-wire magnetic switch by using the Hall element in the above-mentioned constant current drive system, and aiming at high sensitivity, it is necessary to supply a large current Ic to the Hall element. Yes, it is not suitable for the two-wire system. For this reason, when a highly sensitive InSb type Hall element is used, the temperature characteristics are poor, which is a practical problem. However, focusing on the temperature characteristics, there is no choice but to use a low-sensitivity Hall element such as Si type or a high-sensitivity Hall element such as InSb type in a constant voltage drive system.
Then, the sensitivity becomes low.

It is an object of the present invention to improve the problems of the prior art and propose a two-wire magnetic switch using a Hall element which has high sensitivity and high temperature stability and is inexpensive.

[0005]

In order to achieve the above object, the present invention provides two output terminals of a constant current driven Hall element to two input terminals of a differential amplifier via a first resistor, respectively. In a magnetic switch circuit which is connected to the output terminal of a differential amplifier and a second resistor is connected to each of the input terminals, the output voltage appearing at the output terminal is It is characterized in that the first and second resistors are selected so that the amount of change in temperature becomes a predetermined value or less. In the circuit of the present invention, an InSb type Hall element may be used as the Hall element.

[0006]

In the magnetic switch circuit of the present invention, the first and second magnetic switch circuits are provided.
The temperature change of the output voltage becomes equal to or less than a predetermined value only by properly selecting the resistance of the.

[0007]

Embodiments of the present invention shown in the drawings will be described below.
FIG. 1 shows an embodiment of a two-wire magnetic switch circuit according to the present invention, in which a Hall element is used in a constant current drive system. In the figure, 1 is, for example, a high-sensitivity InSb type Hall element, 2 is a constant current source for driving the Hall element 1 with a constant current, and R ₁ is output terminals 1a and 1b of the Hall element 1.
Is a differential resistor, 3 is a differential amplifier, 4 is an output terminal, and R ₂ is a second resistor connected to the two input terminals 3 a and 3 b of the differential amplifier 3.

In the two-wire magnetic switch circuit having the above structure, when the Hall element 1 is placed in the magnetic field B and driven by a constant current, the output voltage Eo appears at the output terminal 3. Eo = {R ₂ / (R ₁ + Rd)} · V _H Rd is the internal resistance of the Hall element 1.

The inventor of the present invention has a characteristic that the internal resistance Rd of the Hall element 1 and the Hall voltage V _H are substantially inversely proportional to the ambient temperature as shown in FIGS. If used, it is possible to minimize the temperature change of the output voltage E _o without using a special temperature compensation circuit by appropriately selecting the first and second resistors R ₁ and R _2. I was able to find out.

That is, if the temperature characteristics of Rd and V _H are linearly approximated and the respective temperature distributions are A and B, then Rd (t) = Rd _o −At V _H (t) = V _H0 −Bt , and the temperature variation dE _o / dt of the E _o is _{E o = {R 2 / (} R 1 + Rd)} · V H dE o / dt = d {R 2 (V H0 -Bt) / dt (Rd ₀ −
At) + R ₁ }, and R ₁ , R such that dE _o / dt is from 0 to the minimum.
There is a value of ₂ . In practice, even if dE _o / dt is not the minimum,
R that is less than a predetermined value that is small enough to suit the application
_It does not matter if the values of ₁ and R ₂ are selected.

For example, an InSb type Hall element is
Assuming that C = 5 mA and B = 500 G (Gauss) are used, the temperature characteristics of Rd and V _H are as follows. Temperature 0 ° 20 ° 40 ° 60 ° C. Rd 550 350 350 230 160Ω V _H 460 350 270 210 mV

[0012] The above R ₁ = 10 k.OMEGA as a Hall element used in the circuit of FIG. 1, R ₂ = 100kΩ and the time of the output voltage _{E o1, R 1 = 0,} R 2 = 5kΩ and the time of the output voltage E The temperature characteristics of ₀₂ are as follows. Temperature 0 ° 20 ° 40 ° 60 ° C. E _o1 4.63 3.38 2.64 2.07 V E _o2 4.18 5.8 5.8 5.87 6.56 V

The output voltage E_o1, E_o2Change with temperature
The quantity is in the opposite direction. This is R ₁, R₂To select the value of
Output voltage E_oShows that the temperature change of
ing. R as an example₁= 200Ω, R₂= 6.5 kΩ
When the temperature is 0 ° 20 ° 40 ° 60 ° C E_o 3.99 4.14 4.08 3.79V, which is the output voltage E due to temperature change._oChanges significantly
Has been reduced.

Next, a Hall effect type position sensor will be described as an application example of the magnetic switch circuit of the present invention. FIG. 4 is a block diagram showing an embodiment of a Hall effect type position sensor using a magnetic switch circuit of the present invention, 11 is a magnetic field generating section made of a permanent magnet which constitutes the object to be detected, and 12 is a magnetic field generating section 11. It is a magnetic field detection unit including a Hall element 15 that slides in the magnetic flux direction 13 relative to each other and that detects the magnetic field from the magnetic field generation unit 11 while maintaining the operating distance h. 14
Is a bias voltage applied to the output voltage of the Hall element 15 of the magnetic field generator 11, as described later. Magnetic field detector 12
As described above, the Hall element 15 constituting the
A semiconductor thin film such as nSb is used. Reference numeral 16 designates a constant current source 2, a resistor R ₁ and a resistor R ₁ , which constitute the magnetic switch circuit of FIG.
This is a circuit including R ₂ and a differential amplifier 3.

5 to 7 show a concrete structure of the magnetic field generator 1. FIG. 5 is a plan view, FIG. 6 is a sectional view taken along line AB of FIG. 5, and FIG. 7 is line CD of FIG. FIG. Reference numeral 16 is, for example, a first 1 made of an anisotropic Ba ferrite magnet having a large coercive force.
The permanent magnets 17, 18 of the first permanent magnet 16 are arranged on both sides along the sliding direction (magnetic flux direction) 13 of the first permanent magnet 16 with equal gaps D (see FIG. 5). These are second and third permanent magnets having a small length dimension and made of the same material as the first permanent magnet 16, and the polarities of the second and third permanent magnets 17 and 18 are the same as those of the first permanent magnet 16. It is magnetized so that the polarity is opposite to that of the polarity. As shown in FIG. 8, the length dimensions of the first, second, and third permanent magnets 16, 17, and 18 along the sliding direction 13 are L ₁ , L ₂ , and L ₃ , respectively, and the height dimension is Assuming that H is H and the width dimension in the direction perpendicular to the paper surface is W, L ₁ = 6 m
m, L ₂ = L ₃ = 3 mm, H = 3 mm, W = 6 mm, D = 3 mm. FIG. 8 shows the magnetic fluxes generated from the permanent magnets 16, 17 and 18 with broken lines B ₁ , B ₂ , B ₃ ... And the characteristics of the Hall output (voltage) experimentally obtained by this magnetic field generation unit 11. The curves are indicated by solid lines C ₁ , C ₂ , C ₃ ... An example is shown in which the magnetic field detection unit 12 is slid with respect to each of the permanent magnets 16, 17, and 18 at a height position that maintains the operating distance h1. The horizontal axis (x axis) is the slide direction,
The vertical axis (y axis) indicates the height direction.

The permanent magnets 16, 17 and 18 are housed in a non-magnetic case 19 made of, for example, plastic and integrally attached to a mounting plate 20 made of a non-magnetic material or a ferromagnetic material. The mounting plate 20 is provided with a positioning hole 21 in advance, and the permanent magnets 16, 17 and 18 are bonded by an adhesive in a state where the projection 22 provided on the bottom of the non-magnetic case 19 is positioned in the hole 21. Non-magnetic case 1
9, integrated with the mounting plate 20. In addition, non-magnetic case 1
A groove 23, which serves as a mark indicating the switching operation range, is provided on the upper surface of 9. It is desirable that the mounting plate 20 be made of a ferromagnetic material such as mild steel due to its characteristics as described later. The mounting plate 20 has an oval mounting hole 24 along the sliding direction.
The mounting plate 20 is fixed to the detected object by screwing the mounting screw 25 into the mounting hole 24. This fixed position can be adjusted by sliding it along the mounting hole 24.

In FIG. 8, solid lines C ₁ , C ₂ , C ₃ ... Show characteristic curves in which the Hall output becomes 0 V, ± 0.1 V, ± 0.2 V, and broken lines B ₁ , B ₂ , B ₃ The magnetic flux of ... is estimated and plotted from the characteristic curve group of the Hall output. Each characteristic curve and magnetic flux are shown symmetrically with the central portion CL of the first permanent magnet 6 as the center. The surface of the Hall element 15 of the magnetic field detection unit 12 which is close to the permanent magnets 16, 17 and 18 with an operating distance h1 is y.
Since it is held perpendicular to the axis, the magnetic flux density B in the vertical direction
Hall output proportional to is obtained. The magnetic flux density B in the vertical direction must be 0 on the characteristic curve of Hall output 0V. The broken lines B ₁ , B ₂ , B ₃ ... Denoting the magnetic flux are plotted so as to be almost the same. The magnetic flux also exists in the downward direction of the x axis, but is omitted.

When the magnetic field detector 12 is slid while keeping the operating distance h, if the magnetic field detector 12 is on the far left side of the origin of x = 0, the vertical magnetic flux density B is 0. Becomes 0V. Sliding magnetic field detecting section 12 to the _{right, P 1, P 2, P} 3, P 4, -0.2V respectively at each point _{P 5, -0.1V, 0V, 0.1V} , 0.
Generates 2V Hall output. Further, by sliding to the _{right, Q 1, Q 2, Q} 3, respectively at each point Q _4, Q ₅ 0.
The Hall outputs of 2V, 0.1V, 0V, -0.1V and -0.2V are generated. A Hall output of 0.2 V or higher is generated between P ₅ and Q ₁ and reaches a maximum of 0.3 V and saturates.

Here, as an actual usage method, a method in which the Hall output performs switching operation at 0 V must be avoided because the operation becomes unstable. This is to prevent this even when the magnetic field detection unit 12 is on the far left side of the y-axis, since the Hall output is 0 and the switching operation is performed. Therefore, in this embodiment, as shown in FIG. 1, when the bias voltage 14 is applied to the Hall element 15, the switching operation is performed when the sum of the bias voltage and the Hall output becomes zero. Is aimed at. As a specific example, if the bias voltage of −0.05 V is applied to the Hall output, the V curves of the solid lines C ₃ and C _{6 in} FIG. 8 become −0.5 V curves, and the solid lines C ₂ and C _{7 of FIG.} The -0.1V curve of is a -0.15V curve. In this way, the output of all the curves is shifted by -0.05V. Therefore, the broken lines C ₁₀ , C ₂₀ of 0.
The 05V curve becomes a 0V curve.

As described above, the operation with the bias voltage applied is as follows. That is, the magnetic field detector 12
Is far to the left of the y-axis, the Hall output is 0
By applying a bias voltage of -0.05V to V, the total output becomes -0.05V. Next, the magnetic field detector 1
When 2 slides to the P ₁ point, the total output in this case becomes −0.25V when −0.05V is applied to −0.2V of C ₁ . Similarly, the total output is -0.15V when the slide at _two points P, the total output when the slide _three points P becomes -0.05 V, intersection between 0.05V curve of broken line C ₁₀ At first, all outputs become 0V, the switching operation is performed, and the control signal is output. Until the magnetic field detector 12 is slid to the right and passes the points Q ₁ and Q ₂ and the intersection of the broken line C ₂₀ , the total output is positive and the switching operation is maintained. Then slide to the right to Q ₃ ,
When Q _4, Q reached ₅ points, the total output is negative, the switching operation is canceled.

As a result, as long as the magnetic field generator 11 slides within the range of the broken lines C ₁₀ and C ₂₀ , the switching operation is maintained, so that a wide switching operation width can be secured. By thus ensuring a wide switching operation width, a reliable operation as a position sensor can be enabled, and the detected object can be stopped at a predetermined position. In this respect, if the switching operation width is narrow, the position sensor cannot reliably operate, and it becomes difficult to stop the detected object at a predetermined position. Further, since the 0.05V curve of the broken lines C ₁₀ and C ₂₀ can be made into a shape close to an ideal that is almost vertical,
Even if the magnetic field detection unit 12 changes in the y-axis direction, that is, even if the operating distance h1 between the magnetic field generation unit 11 and the magnetic field detection unit 12 changes, it is possible to suppress the deviation of the detection position in the slide direction to be small. Therefore, the detection accuracy can be improved. As a result, the operating distance h1 can be increased. In this respect, when the permanent magnets forming the magnetic field generating unit are closely adhered to each other without providing a gap as in the conventional case, the 0V curve is largely inclined to the outside, so it is assumed that an appropriate bias voltage is applied. Also 0
Since it is difficult to make the V-curve ideally close to vertical,
The operating distance cannot be increased.

The reason why the 0V curve can be idealized as described above is that the 0V curve of the solid lines C ₃ and C ₆ in FIG. 8 is slightly inclined outward.
This is because the length dimensions L ₂ and L ₃ of the second and third permanent magnets 17 and 18 are set to be smaller than the length dimension L ₁ of the first permanent magnet 6, and a gap D is provided. It is because of that. In this embodiment, when the current directions of the Hall elements 15 of the magnetic field detector 12 are reversed, the signs of the characteristic curves are all reversed. Further, in this case, +0.05 V is applied as the bias voltage. As a result, the total output output in the switching operation range between the solid lines C ₁₀ and C ₂₀ becomes negative.

As in the present embodiment, each permanent magnet 16, 17,
By storing 18 in the non-magnetic case 19, the amount of iron powder adsorbed from the surroundings can be reduced. Even if it is adsorbed, its removal is easy. Also,
When a ferromagnetic material such as mild steel is used as the mounting plate 20,
Since the magnetomotive force of the permanent magnet is hardly consumed in the mild steel, the total magnetomotive force acts on the upper surface of the permanent magnet, so that the operating distance h1 can be increased. Furthermore, the mounting plate 20
In many cases, is attached to a steel material, but if mild steel is used, the change in magnetic field due to attachment can be reduced.

According to the embodiment of FIG. 4, the displacement of the magnetic field detector 12 from the first permanent magnet 16 in the left-right direction, that is, from the second and third permanent magnets 17 and 18 side. Although the switching operation of the response was two points (C _10, C ₂₀₎ (switching operation symmetric) is obtained, depending on the application, the switching operation at one place in response to one direction of displacement is obtained In some cases it may be enough. In such a case, as shown in FIG. 9A or 9B, only the second or third permanent magnet 17 or 18 may be provided.

Next, an example in which the magnetic switch circuit of the present invention is applied to a linear displacement sensor will be described. FIG. 10 shows an embodiment of a linear displacement sensor using the magnetic switch circuit of the present invention, in which 31 is a magnetic field generating section which constitutes the object to be detected, and the magnetic field generating section 31 is a first permanent magnet 32 and this A second permanent magnet 34 which is coupled to the first permanent magnet 32 via a magnetic body 33 and is arranged along the displacement direction X. The second permanent magnet 34 is magnetized so that the polarities thereof are opposite to each other. 35
Is the displacement direction X relative to the magnetic field generator 31.
It is a magnetic field detection unit including a Hall element 36 that slides to a position and detects a magnetic field from the magnetic field generation unit 31 while maintaining a constant working distance h and outputs an electric signal. A signal processing circuit 37 processes the detection signal of the hall element 36, and has the constant current source 2, resistors R ₁ and R ₂ , and a differential amplifier 3 shown in FIG. A semiconductor thin film such as InSb is used for the Hall element 36 that constitutes the magnetic field detection unit 35. This Hall element 36 detects the magnetic field from the magnetic field generation unit 31 by the Hall effect and detects an electric signal (mostly a DC voltage or a DC voltage). The displacement of the detected object is detected by outputting (current).

FIG. 11 illustrates the principle of operation of the embodiment of FIG. 10. When the magnetic field detector 35 is slid along the displacement direction X while keeping a constant operating distance h, the Hall element 36 moves to the first position. When located at an intermediate position C between the permanent magnet 32 and the second permanent magnet 34, the first permanent magnet 32 and the second permanent magnet 34
Hall voltage Vh detected by the Hall element 36 based on the fact that the magnetic flux direction of the permanent magnet 34 of
That is, the output voltages become zero because they cancel each other out. On the other hand, when the Hall element 36 slides to the left in the figure from this position, the magnetic flux of the first permanent magnet 32 penetrates the Hall element 36 from the bottom to the top, so that the Hall element 36 has a positive Hall voltage Vh (output voltage). To detect. Conversely, when the Hall element 36 slides to the right in the figure, the magnetic flux of the second permanent magnet 34 penetrates the Hall element 36 from the top to the bottom, so the Hall element 36 detects the negative Hall voltage Vh (output voltage). To do. As a result, an S-shaped output curve as shown is obtained corresponding to the slide position of the Hall element 36. This output curve changes substantially linearly in the range M near the intermediate position C. Therefore, a linear output characteristic can be obtained by combining the relationship between the movement of the Hall element 36 at the intermediate position C and the Hall voltage that changes substantially linearly and continuously. The positive and negative polarities of the output voltage can be easily inverted in a circuit manner if necessary.

FIG. 12 shows the result of the first experiment in the present embodiment. The first and second magnetic field generating parts 31 are constituted.
The permanent magnets 32, 34 of the length L ₁ , L ₂ , both magnets 32, 3
4 shows output characteristics obtained when the dimensions of the gap D between 4 and the operating distance h are set to values as shown in the figure. The horizontal axis represents the slide position (mm) of the Hall element 36, and the vertical axis represents the output voltage (mV). In addition, FIG. 12 shows a second experimental result in the present embodiment, in which the lengths L ₁ and L ₂ , the gap D, and the operation of the first and second permanent magnets 32 and 34 forming the magnetic field generator 31 are shown. It shows the output characteristics obtained when the respective dimensions of the distance h are set to the values shown in the figure. A linear output characteristic is obtained in both FIG. 12 and FIG.

As described above, according to the present embodiment, by combining the first and second permanent magnets 32 and 34 and the Hall element 36 to form a linear displacement sensor, the permanent magnets 32 and 34 and the Hall element 36 are connected. As the element 36, an inexpensive and high-performance element can be easily obtained, so that the cost can be reduced. Further, by combining the permanent magnets 32 and 34 and the Hall element 36, the displacement of the object to be detected can be detected without the need for a complicated circuit configuration, so that a small linear displacement sensor can be realized.

A wide linear output range can be ensured by using strong permanent magnets as the first and second permanent magnets 32 and 34 constituting the magnetic field generator 31 and setting a large gap between them. it can. Further, by using small and strong permanent magnets as the permanent magnets 32 and 34 and setting the gap between them to be small, a smaller linear displacement sensor can be obtained.

[0030]

As described above, according to the present invention, the following excellent effects can be obtained. (1) The Hall element can be driven with a constant current so as to obtain good temperature characteristics. Therefore, when it is used in a two-wire magnetic switch circuit, the current when it is off can be reduced. Further, the Hall element of InSb type has a large electron mobility and the highest sensitivity, but the temperature characteristic is not good because of the small band gap width. However, according to the present invention, use of this type is preferable. You can (2) A temperature compensating circuit and parts having a complicated structure are unnecessary, and the cost is low. (3) The temperature dependence of the switch operating point is reduced, and stable operation can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a temperature characteristic diagram of internal resistance of a Hall element.

FIG. 3 is a temperature characteristic diagram of Hall voltage of a Hall element.

FIG. 4 is a configuration diagram showing an embodiment of a Hall effect type position sensor as an application example of the present invention.

FIG. 5 is a plan view showing a configuration of a magnetic field generation unit of the sensor.

6 is a cross-sectional view taken along the line AB of FIG.

7 is a cross-sectional view taken along the line C-D of FIG.

FIG. 8 is a characteristic diagram of a Hall output obtained by the sensor.

FIG. 9 is a configuration diagram showing a modified example of the sensor.

FIG. 10 is a configuration diagram showing an embodiment of a linear displacement sensor as an application example of the present invention.

FIG. 11 is an operation explanatory diagram of the sensor of FIG.

FIG. 12 is an output characteristic diagram showing a first experimental result of the sensor of FIG.

FIG. 13 is an output characteristic diagram showing a second experimental result in the sensor of FIG.

FIG. 14 is a diagram for explaining a Hall effect.

[Explanation of symbols]

1 Hall element 2 Constant current source 3 Differential amplifier R ₁ 1st resistance R ₂ 2nd resistance

Claims (5)

[Claims] 1. Two output terminals of a constant current driven Hall element are connected to two input terminals of a differential amplifier via a first resistor, and a second resistor is connected to each of the input terminals. In a magnetic switch circuit which is connected and one of the second resistors is connected to an output terminal of a differential amplifier, the first switch is configured so that the temperature change amount of the output voltage appearing at the output terminal becomes a predetermined value or less. And a second resistor, a two-wire magnetic switch circuit using a Hall element. 2. The two-wire magnetic switch circuit using the hall element according to claim 1, wherein the hall element is an InSb type hall element. 3. A magnetic field generation unit composed of a permanent magnet that constitutes the object to be detected, and a magnetic field detection unit composed of a Hall element that slides relative to the magnetic field generation unit and detects a magnetic field from the magnetic field generation unit. In the Hall effect type position sensor having the above structure, the magnetic field generating unit includes a first permanent magnet and a first permanent magnet arranged at equal gaps on both sides of the first permanent magnet in a sliding direction of the first permanent magnet. A second permanent magnet and a third permanent magnet having a length smaller than that of the magnet,
The permanent magnets are magnetized so that the polarities of the second and third permanent magnets are opposite to the polarities of the permanent magnets, and the magnetic field detecting unit has two output terminals of the Hall element driven by constant current. Each of them is connected to two input terminals of the differential amplifier via a first resistor, and a second resistor is connected to each of the input terminals and one of the second resistors is connected to an output terminal of the differential amplifier. , And a magnetic switch circuit connected to the common ground of the differential amplifier, respectively, so that the temperature change amount of the output voltage appearing at the output terminal becomes equal to or less than a predetermined value. Hall effect type position sensor characterized by selecting. 4. A linear displacement sensor for continuously detecting a displacement of an object to be detected and outputting an electric signal, comprising: a first permanent magnet, and a first permanent magnet which is adjacent to the first permanent magnet and extends along the displacement direction. A magnetic field generating unit that is disposed and that has a second permanent magnet that is magnetized so as to have a polarity opposite to that of the first permanent magnet, and that constitutes a detection target, and a magnetic field generating unit for the magnetic field generating unit. And a magnetic field detection unit including a Hall element that relatively slides in the displacement direction and detects a magnetic field from the magnetic field generation unit while maintaining a constant operating distance and outputs an electric signal. Connects the two output terminals of the constant current driven Hall element to the two input terminals of the differential amplifier via the first resistor, respectively, and connects the two output terminals of each of the input terminals to the second input terminal of the differential amplifier.
And a magnetic switch circuit in which one of the second resistors is connected to the output terminal of the differential amplifier, and the temperature change amount of the output voltage appearing at the output terminal is below a predetermined value. A linear displacement sensor, wherein the first and second resistors are selected. 5. A magnetic field generation unit composed of a permanent magnet that constitutes the object to be detected, and a magnetic field detection unit composed of a Hall element that slides relative to the magnetic field generation unit and detects the magnetic field from the magnetic field generation unit. In the Hall effect type position sensor having the above structure, the magnetic field generating unit includes a first permanent magnet and a first permanent magnet arranged at equal gaps on both sides of the first permanent magnet in a sliding direction of the first permanent magnet. It is composed of a second permanent magnet having a length smaller than that of the magnet, and is magnetized so that the polarity of the second permanent magnet is opposite to the polarity of the first permanent magnet. The section connects two output terminals of a constant current driven Hall element to two input terminals of a differential amplifier via a first resistance, and connects a second resistance to each of the input terminals. Together with one of the second resistors of the differential amplifier A hall including a magnetic switch circuit connected to an output terminal, wherein the first and second resistors are selected so that a temperature change amount of an output voltage appearing at the output terminal is equal to or less than a predetermined value. Effective position sensor.