BG1196U1 - Magnetoresistive sensor for measuring the magnitude (absolute value) of magnetic field - Google Patents

Abstract

The magnetoresistive sensor is designed for positioning of moving magnetic parts. The sensor according to the utility model comprises a basic sensitive element embodied in the form of a thin- or thick-film structure of magnetoresistive material with anisotropic magnetoresistive effect. The basic sensitive element is in the form of an arched bus with an arc angle of 180 degrees, with a length / width ratio greater than 10, and an anisotropy axis following the curvature of the arc. In an embodiment, a magnetoresistive sensor is described whose basic element of 180 degrees is divided into two complementary segments: an arch with an arc angle of 90 degrees and an arch with an arc angle of 90 degrees, which are turned at 90 degrees to one another.

Description

Technical field

The utility model refers to a magnetoresistive sensor designed for the positioning of moving magnetic parts and is used in the automated control of technological processes, in devices and systems for material and flaw analysis, in automotive and transport, for measuring non-electrical quantities (flow , volume, distance, speed), in security and home appliances, etc.

BACKGROUND OF THE INVENTION

Known magnetoresistive sensors [1,2,3] for use in the positioning of linearly moving magnetic parts whose action is based on the so-called anisotropic magnetoresistance AMR manifested in thin layers of some ferromagnetic materials e.g., NiFe perm.). The base sensing element is a rectilinear, long-width / rectangular thin-film strip. Such a bar is distinguished by a straight axis of magnetic anisotropy oriented parallel to the length of the bar. In order to achieve high resistance and consequently reduce the current consumption, a number of such bars arranged parallel to each other are connected in series and form a magnetoresistor with the meander configuration. The sensor consists of four such magnetoresistors connected by a Wheatstone bridge circuit, each of the bridge arms consisting of two magnetoresistors with complementary (complementary) behavior. Complementarity is achieved by the proper orientation (rotation) of the meander structures (eg at 45 ° to each other) or by using the so-called. barber pole shunt contacts that divert current through a bar 45 ° from the geometric axis of the bar. The connection by the Wheatstone bridge provides compensation for the temperature dependence of the resistance of the individual resistors and, accordingly, the temperature independence of the output signal.

An exemplary embodiment of the problem of positioning a linearly moving magnetic part is shown in FIG. 1. Magnet 1 with the magnetization NS shown in the figure moves linearly along the x-axis. At a certain distance along the y-axis of the magnet is a magnetic sensor 2. The task is to determine the location of the magnet at a given moment by the signal received from the sensor. The absolute value (magnitude) H of the magnetic field vector at the point where the sensor is located grows monotonically as the magnet approaches the sensor and has a maximum value at zero distance between them along the axis of motion, as shown in FIG. 2. The two components of the vector in the plane of the sensor (Hx and No), which define the direction of the field, have a much more complex move shown in Figs. 3. The physical mechanisms operating in the sensors presented above suggest sensitivity not only to the magnitude of the magnetic field but also to the ratio of the individual components Hx and Nu. Hence the complex and ambiguous nature of the received signal, which requires more sophisticated signal processing and certain limitations in the application of the sensors. An exemplary signal is presented in FIG. 4.

The technical nature of the utility model

The magnetoresistive sensor for measuring the magnitude of a magnetic field, according to the present utility model, includes a basic sensing element made of a thin-layer or thick-layer structure of magnetoresistive material with an anisotropic magnetoresistive effect. The basic sensing element is in the form of an arcuate bar with an arc angle of 180 °, with a length / width ratio> 10 and an anisotropy axis following the curvature of the arc. The base element is provided with contact pads located at both ends.

As a special case, a magnetoresistive sensor is presented, the 180 ° base element of which is divided into two complementary segments: an arc segment with an arc angle of 90 ° and an arc segment with an arc angle of 90 ° and rotated 90 ° relative to the segment.

1196 Sh

Explanation of the annexed figures

Figure 1 is a representation of the task of positioning a linearly moving magnetic workpiece;

FIG. 2 is a variation of the magnitude H (absolute value) of the magnetic field at the location of the sensor and depending on the distance of the magnetic sensor; FIG.

Figure 3 is a variation of the magnetic field components Hx and Nu at the point of sensor location and depending on the distance of the magnetic sensor;

4 is an exemplary signal S of an existing sensor when positioning a linearly moving magnetic part;

Figure 5 shows a base element of magnetoresistive material with an arc angle of 180 °;

Figure 6 - complementary magnetoresistors with meander configuration;

7 is an exemplary embodiment of a magnetoresistive sensor sensitive to the absolute value of the magnetic field.

Examples of implementation of the utility model

Figure 5 shows an exemplary embodiment of a 180 ° base element. The basic sensing element is in the form of an arcuate bar 3 with an arc angle of 180 °, with a length / width ratio = 12 and with an anisotropy axis 4 following the arc curvature. The base element is provided with contact pads 5 located at its two ends. The 180 ° base element is fed from a DC source and the voltage drop measured on the element. The change in the voltage drop due to the applied magnetic field depends only on the magnitude (the absolute value of the field intensity) and does not depend on its direction. Another embodiment is based on the separation of the base element into two 90 ° segments. In FIG. 6 depicts two complementary magnetoresistors of meander configuration: a magnetoresistor 6 consisting of parallel segments 7 (90 ° arc angle) and a magnetoresistor 9 consisting of parallel segments 10 (90 ° angle and rotation 90 °). segments 7). The constituent segments of each of the two resistors are connected in series by a wiring harness 8 made of non-magnetic material. According to this exemplary embodiment shown in FIG. 7, the sensor is an integral thin-film structure in the form of a Wheatstone bridge, consisting of:

• magnetoresistors 11 and 13 of the type of resistor 6 described above (Fig. 6) with resistors R11 and R13 respectively;

• magnetoresistors 12 and 14 of the type of resistor 9 described above (Fig. 6) with resistors R12 and R14 respectively;

• two magnetic screens 15 deposited on magnetoresistors 13 and 14;

• connecting strips 16 of non-magnetic material;

• Non-magnetic contact pads 17,18,19,20.

All resistors involved in the circuit are designed to have the same resistance (R11 = R12 = R13 = R14) in the absence of a magnetic field. The magnetoresistors 11 and 13 make up the left arm of the bridge, and the magnetoresistors 12 and 14 the right arm. Thus, one-arm resistors have the same structure and are made of the same material, which ensures the temperature stability of the output signal. The magnetoresistors 13 and 14 are coated with layered magnetic screens 15 which make them passive (insensitive to applied magnetic fields). Thus, the left arm of the bridge consists of one active (magnetic-sensitive) resistor 11 in the lower position and one passive resistor 13 in the upper. The right arm consists of the active resistor 12 in the upper position and the passive resistor 14 in the lower position. When applying a supply voltage Vs (eg potential Vs at terminal 17, potential 0 to terminal 19) and in the absence of a magnetic field, the same potentials are obtained at the midpoints of the two arms (V _L for left arm, V _R for right arm , such as V _L = V _R = Vs / 2), which are fed respectively to pin 18 on the left arm and pin 20 - to the right. In the presence of a magnetic field, the change of V _L follows the course of the change of Rl 1 (corresponding to the behavior of Segment 1 described above), with the decrease of Rl 1 leading to a decrease of V. The potential V _n follows the changes of R12 (corresponding to the

1196 Segment 2), but in counter-phase (decreasing R12 leads to an increase in V _R ). The output signal S = V _L - V _R thus measured is the result of the total change of R11 and R12 and demonstrates the behavior of the entire base element described above, ie. depends on the magnitude of the applied magnetic field and does not depend on its direction. When positioning a linearly moving magnetic part, the signal S follows the course of H shown in FIG. 2.

Application of utility model

The utility model will find application for the effective positioning of linearly moving magnetic parts for the purpose of automatic control, as well as for solving other problems of automation and analytical techniques that require a signal dependent on the magnitude and independent of the direction of the magnetic field.

The basic sensing element is a thin-film structure of material having an anisotropic magnetoresistive effect (eg permalloy) and having the form of an arcuate bar with an angle of 180 ° and a length / width ratio> 10. The axis of magnetic anisotropy is curved, following the geometry of the bar, as shown in FIG. 5. Due to the symmetry of the anisotropic magnetoresistive effect, the magnetic variation of the resistance of the base element depends only on the magnitude H (modulus H of the magnetic field vector) and does not depend on the direction of the field. Under the condition of the linear positioning of moving magnetic parts, the course of the magnetoresistive effect (the magnetic variation of the resistance) has the character of the stroke of H shown in FIG. 2 (monotonically increasing as the magnet approaches the sensor), which provides a single position determination of the magnet and facilitates signal processing.

In order to take advantage of the meander structures (obtaining optimum resistance at optimum structure area), the base element is divided into two segments (Segment 1 - arc with 90 ° angle and Segment 2 arc with 90 ° and rotate 90 ° Segment 1) from which two complementary magnetoresistors are constructed in the form of meanders, as shown in FIG. 6. The number of arcs and dimensions of each meander is determined by the set resistance and magnetic sensitivity of the magnetoresistor. The total magnetoresistive effect of the two magnetoresistors is equal to the magnetoresistive effect demonstrated by the 180 ° base element. The two complementary magnetoresistors may be located respectively on the left and right arms of the Wheatstone Bridge to obtain a magnitude-dependent differential output signal independent of the direction of the applied magnetic field.

Claims (2)

Claims A magnetoresistive sensor for measuring the magnitude of a magnetic field, comprising a base sensing element of a magnetoresistive material with an anisotropic magnetoresistive effect, characterized in that the basic sensing element has a thin or thick layer structure and an arc-shaped bar (180) and a length / width ratio> 10. A magnetoresistive sensor according to claim 1, characterized in that the base element is divided into two segments - arcs (6, 9) with 90 ° angles, arranged relative to each other at 90 °, on the basis of which two magnetoresistors with meander structure, with magnetoresistors located in complementary positions on the left and right arms of the Wheatstone Bridge, respectively. Attachment: 7 figures