EP1751501A2

EP1751501A2 - Sensor element and associated angle measurement system

Info

Publication number: EP1751501A2
Application number: EP05753018A
Authority: EP
Inventors: Reinhard Buchhold
Original assignee: Philips Intellectual Property and Standards GmbH; Koninklijke Philips Electronics NV
Current assignee: NXP BV
Priority date: 2004-05-14
Filing date: 2005-05-03
Publication date: 2007-02-14
Also published as: WO2005111546A3; WO2005111546A8; JP2007537437A; WO2005111546A2; CN1954194A

Abstract

In order to provide at least one magnetoresistive sensor element (100, 110) which - by means of at least one supply terminal (10, 14), and at least one reference terminal (12, 16), can be supply with at least one supply voltage (VCC; VCC1; VCC2) and at least one supply current (i; i1, i2), respectively, - wherein the differential voltage (Vout; Vout1; Vout2) which is set as a function of the angle (α; α1; α2) -- between the direction (D; D1; D2) of the drop in the supply voltage (VCC; VCC1; VCC2) or flow of the supply current (i; i1; i2) -- and the direction of the resulting internal magnetic field (Hres) can be tapped between at least a first tapping electrode (20, 24) and at least a second tapping electrode (22, 26) and - wherein the direction of the resulting internal magnetic field (Hres) is given by superposing the intrinsic magnetization (H0) and at least one external magnetic field (Hext), which can be produced without a preferred magnetic orientation and in which the technologically induced offset is minimized or eliminated, the magnetoresistive sensor element (100, 110) is designed to be flat, in particular the drop in the supply voltage (VCC; VCC1; VCC2) is continuous.

Description

Sensor element and associated angle measurement system

The present invention relates to a magnetoresistive sensor element as claimed in the preamble of claim 1. Contactless angle measurement is a main field of application of magnetoresistive sensors. The reason for this is that the solid state effect on which the magnetoresistive sensor is based is an angle effect:

p(a{i, H_at )) = p + (pu - Px)- cos² (a(i, _exl)) = p₁ Sensor elements which measure magnetic fields (so-called A[nisotropic]M[agneto]R[esistive] sensors) are based on the principle of the anisotropic magnetoresistive effect. At present, as described for example in document DE 101 04 453 Al, AMR angle sensors are primarily designed as full Wheatstone bridges. The transfer function of such a full Wheatstone bridge is given by the equation " out 1 Δ cos (2 )+ V₀ Vcc 2 p_x However, it is disadvantageous that technological tolerances exist during manufacture of the individual narrow and long resistors of the Wheatstone bridge circuit; these tolerances give rise to unavoidable asymmetries in the resistors, so that electrical offsets Vo arise. These offsets already exist with a few millivolts per volt (mV/V) almost in the order of magnitude of the signal amplitude, determined by the AMR effect Δp/p of the Wheatstone bridge of approximately twelve millivolts per volt (12 mV/V), so that the elimination of such offsets during subsequent signal conditioning and processing requires an excessively high degree of complexity. A further disadvantage of bridges known to date is that the linear or bar- shaped resistors have non-negligible intrinsic (or internal) field strengths Ho with H₀ = — - M , w where . p. thickness of the linear or bar-shaped resistor, w: width of the linear or bar-shaped resistor, M: saturation magnetization of Permalloy (approximately 800 kiloamperes/meter), which via the equation

lead to a difference between the angle of the internal magnetization and the angle of the external field. Odd harmonics of the bridge output voltage and thus additional oscillating angle errors result therefrom. Since, therefore, in the Wheatstone bridge circuit the resistors are designed in the form of discrete long strips and the specific design of the resistors with a preferred magnetic direction affects the magnetic transfer characteristics, magnetoresistive sensors which are based on the principle of the Wheatstone bridge circuit exhibit undesirable scattering in the output signal; in particular, the ratio of the particularly highly affected and thus problematic edge regions of the Wheatstone bridge circuit to the inner regions of the Wheatstone bridge circuit impairs the output signal of the magnetoresistive sensors. Based on the abovementioned disadvantages and shortcomings and in acknowledgement of the outlined prior art, it is an object of the present invention to provide a magnetoresistive sensor element which can be produced without a preferred magnetic orientation and in which the technologically induced offset is minimized or even completely eliminated.

This object is achieved by a magnetoresistive sensor element having the features specified in claim 1, by an angle sensor having the features specified in claim 6 and by an angle measurement system having the features specified in claim 10. Advantageous embodiments and expedient developments of the present invention are characterized in the respective dependent claims. The present invention is based on the fact that the magnetoresistive sensor element is designed in the form of a two-dimensional structure and in particular is flat. Use is thus made, instead of a number of linear or bar-shaped bridge resistors (--> formation of a Wheatstone bridge), of at least one flat, in particular anisotropic, M[agneto]R[esistive] element. This two-dimensional structure or the flat design of the magnetoresistive sensor element has two critical advantages compared to the Wheatstone bridge, namely - smaller technologically induced electrical offsets Vo and - smaller angle errors caused by the internal field Ho- According to the invention, therefore, layouts without a preferred magnetic direction are achieved (in AMR Wheatstone bridges according to the prior art, such preferred magnetic directions cause oscillating angle errors). The occurrence of undesirable scattering in the output signal is thus eliminated by the flat design of the sensor element. Furthermore, on account of the flat design of the sensor element, the supply voltage of the magnetoresistive sensor element advantageously falls continuously. According to one particularly preferred embodiment of the present invention, the intrinsic magnetization H₀ has a low field strength, so that the resulting internal magnetization H_res is aligned essentially parallel to the external magnetic field H_ext. Furthermore, in one advantageous embodiment of the sensor element according to the present invention, the direction of the gradient of the differential voltage is oriented essentially perpendicular to the direction of the drop in the supply voltage or flow of the supply current. Advantageously, the sensor element is formed at least partially of at least one ferromagnetic alloy, for example of Permalloy. The nickel-iron alloy Permalloy (Ni₈oFe₂₀) offers the advantage of high magnetic permeability while at the same time having a low field strength and a low hysteresis loss. The magnetic properties of such a ferromagnetic structure can be tailored by the external shape. Furthermore, when passed through by a magnetic field, Permalloy has the property of altering the ohmic resistance by a few percent. In one essential embodiment of the present invention, the sensor element may be designed to have four or more poles, in particular with a supply terminal and with a signal tap. In this case, the sensor element advantageously has at least one ground point for forming a fixed voltage potential. In one advantageous embodiment of the present invention, the sensor element may be designed to be essentially rectangular or essentially circular. Independently thereof or in conjunction therewith, the sensor element advantageously has no preferred magnetic orientation. The present invention furthermore relates to an angle sensor for measuring magnetic field strengths, in particular the temporal gradient of magnetic field strengths, having at least one sensor element of the type mentioned above. Such an angle sensor may also be designed such that not only a single supply voltage can be applied or not only a single supply current flows; rather, in one expedient embodiment the angle sensor may be designed such that the direction of the drop in a first supply voltage or flow of a first supply current is rotated or offset by a defined angle, for example by 45 degrees, with respect to the direction of the drop in a second supply voltage or flow of a second supply current. In this connection, the angle sensor may advantageously have - a first sensor element assigned to the first supply voltage or to the first supply current and additionally - a second sensor element assigned to the second supply voltage or to the second supply current. Alternatively, in one expedient embodiment of the angle sensor, the first supply voltage or the first supply current and the second supply voltage or the second supply current may also be assigned to one and the same sensor element, for example by means of terminals that are rotated or offset in each case by the defined angle, for instance by 45 degrees. The present invention furthermore relates to a contactless angle measurement system, having - at least one angle sensor of the type mentioned above and - at least one circuit arrangement, in particular at least one integrated circuit, which can be supplied with at least one output signal of the angle sensor and is provided to evaluate the output signal. The present invention finally relates to the use of at least one sensor element of the type mentioned above and/or of at least one angle sensor of the type mentioned above and/or of at least one angle measurement system of the type mentioned above - for detecting at least one reference mark when measuring at least one crankshaft angle, - for detecting metallic objects, - for measuring rotation speeds and/or currents, - for detecting weak magnetic fields, for example for detecting small movements and/or changes in active components of cars or machines, such as for example of at least one drive, of at least one metal rod, of at least one cam, of at least one wheel or of at least one gearwheel, - for detecting and/or controlling traffic movements, - for navigation purposes, for example using at least one compass, or - for contactless angle measurement. The magnetoresistive sensor device (or the magnetoresistive sensor element) of the type mentioned above and/or the angle sensor of the type mentioned above and/or the angle measurement system of the type mentioned above may advantageously also be used - as a proximity sensor, - as a motion sensor or - as a position sensor.

In this case, use is advantageously made of an external magnetic field which, in the event of a change in the position of the object that is to be detected relative to the source of the external magnetic field, gives rise to a proportional voltage signal of the sensor element.

As already mentioned above, there are various possibilities for advantageously configuring and developing the teaching of the present invention. In this respect, on the one hand reference is made to the claims dependent on claim 1, claim 6 and claim 10 and on the other hand further embodiments, features and advantages of the present invention will be described in more detail below with reference inter alia to the exemplary implementation of a number of examples of embodiments shown in Figs. 1 to 6. Fig. 1 schematically shows a first example of embodiment of a magnetoresistive sensor element according to the present invention. Fig. 2 diagrammatically shows the angle between the supply current and the external magnetic field, plotted against the standardized output signal of the sensor element of Fig. 1. Fig. 3 schematically shows a second example of embodiment of a magnetoresistive sensor element according to the present invention. Fig. 4 schematically shows an example of embodiment of a contactless angle measurement system according to the present invention, having an example of embodiment of an angle sensor according to the present invention with two sensor elements of Fig. 1 or of Fig. 3, wherein the two sensor elements are arranged offset by an angle of 45 degrees with respect to one another. Fig. 5 diagrammatically shows the angles l and α2 to be determined, in each case plotted against the standardized output signal of the sensor element of Fig. 4. Fig. 6 schematically shows a third example of embodiment of a magnetoresistive sensor element according to the present invention. Fig. 7A schematically shows an angle sensor according to the prior art in the form of a so-called double bridge. Fig. 7B schematically shows the circuit arrangement of a Wheatstone bridge according to the prior art for the angle sensor of Fig. 7 A.

Identical or similar configurations, elements or features are provided with identical references in Figs. 1 to 7B. Three examples of embodiments of a sensor element 100 according to the invention are given below. In order to avoid superfluous repetitions, the following explanations with regard to the configurations, features and advantages of the present invention relate (unless stated otherwise) - to the first example of embodiment of the magnetoresistive sensor element 100 as shown in Fig. 1 - and to the second example of embodiment of the magnetoresistive sensor element 100 as shown in Fig. 3 - and to the third example of embodiment of the magnetoresistive sensor element 100 as shown in Fig. 6. In the first example of embodiment as shown in Fig. 1, the sensor element 100 is designed as a flat, essentially rectangular A[nisotropic]M[agneto]R[esistive] element, wherein in this case the AMR effect is shown 50 times greater than it is. This AMR element 100 is supplied via a supply terminal 10 and via a reference terminal 12 at ground potential GND respectively with a supply voltage VCC (hereinbelow also given as Vcc) and with a supply current i brought about by the supply voltage VCC. In this case, the terminals 10 and 12 are opposite one another and are in each case arranged approximately in the center of the side of the AMR element 100 that has the width w. The principle of the AMR element 100 is based on the fact that by superposing an intrinsic magnetization H₀ of the AMR element 100 and an external magnetic field H_ext a resulting internal magnetic field H_res is produced. Since in the AMR element 100 as shown in Fig. 1 the characteristic intrinsic field strengths H₀ are low (<--> no preferred magnetic direction), the resulting internal magnetization H_res is aligned approximately parallel to the external field H_ext even at low field strengths, that is to say the direction of the resulting internal magnetization H_res corresponds to the direction of the external magnetic field H_ext. The AMR element 100 thus has the conductivity p« in the direction of the external field H_ext and the conductivity p perpendicular thereto. Depending on the angle α between the direction D (= predefined direction of current flow or direction of the voltage drop between the supply voltage VCC and ground potential GND, that is to say between the supply terminal 10 and the reference terminal 12) and the direction of the external field H_ext (= essentially the direction of the resulting internal magnetic field H_reS), a differential voltage V_out (so-called pseudo-Hall voltage) is set in the AMR element 100, said voltage being described by the following equation in a form standardized to the supply voltage VCC: where f. (geometry) correction factor between 0 and 1, w: width of the AMR sensor element 100 (defined transversely to VCC-GND), : length of the AMR sensor element 100 (defined along VCC- GND). On account of the external magnetic field H_ext with a given field angle, different conductivities in the AMR element 100 are thus set, for example when the AMR element 100 is moved. These conductivities can be tapped in the form of the differential voltage output signals V_out- For this purpose, the AMR element 100 has two tapping electrodes 20, 22 which lie opposite one another, namely - one positive tapping electrode 20 (for the tap V+ for tapping the positive differential voltage V_out) and - one negative tapping electrode 22 (for the tap V- for tapping the negative differential voltage V_out). The two tapping electrodes 20, 22 are in each case arranged approximately in the center on the side of the AMR element 100 that has the length 1. In Fig. 1, the isopotential lines of the AMR sensor 100 are shown using different colors. Here, the outer limits of a color strip in each case correspond to an isopotential line, wherein the voltage drop from full supply voltage VCC (= 100% VCC) to ground potential GND (= 0% VCC) is shown once again by the strip at the right-hand edge of Fig. 1. Fig. 2 shows the relation between the (standardized) output signal V_out of the AMR element 100 and the angle α of the external field H_ext or of the resulting internal magnetic field H_res. This relation can be attributed to the fact that the resistance R or the specific resistance p of a magnetic conductor changes when an external magnetic field H_ext is applied: When an external magnetic field H_ext is applied parallel to the plane of the magnetic conductor and perpendicular to the current i flowing in the magnetic conductor, the vector of the internal magnetic field H_res of the magnetic conductor rotates by an angle α. The resistance R or the specific resistance p of the magnetic conductor can therefore be placed in relation with the angle α in accordance with the following equation: where p« material constant, p : material constant. The differential output signal V- or V+ of the AMR element 100 is proportional to sin2α, which is why the AMR element 100 shown in Fig. 1 can detect an angle range of ninety degrees (cf. Fig. 2). In Fig. 2, the angle α of the external field H_ext (with respect to the direction D of the current flow i) is plotted on the abscissa and the standardized differential output voltage V_out of the AMR element 100 shown in Fig. 1 is plotted on the ordinate. The amplitude of the illustrated output signals of the AMR element 100 is 9.5 mV/V, which corresponds to approximately eighty percent of the AMR effect (of about 12 mV/V). The transfer characteristic of a flat AMR angle sensor element 100 corresponds to that of the known Wheatstone bridges (cf. prior art). The transfer function of the AMR angle sensor element 100 thus reads out ₌ .^P . _∞s(2a)+ V₀. Vcc 2 p_x Given a slightly lower amplitude, considerably lower offsets Vo are produced on account of manufacturing influences for the flat and/or two-dimensional AMR structure 100 than in the case of full bridges consisting of linear individual resistors. The use of flat AMR elements 100 instead of linear resistors (cf. prior art: Fig. 7 A and Fig. 7B) thus reduces undesirable electrical offsets while having a comparable useful amplitude. As a result, the efficiency when manufacturing AMR angle sensors can be increased and the complexity during subsequent signal processing can be reduced. A further advantage of the novel two-dimensional AMR elements 100 is that they can be produced without a preferred magnetic orientation. In conventional Wheatstone bridges, such a preferred orientation leads to oscillating angle errors with amplitudes of up to 0.3 degrees. Furthermore, on account of the described flat design of the AMR element 100, the temperature coefficients of the electrical offsets are also lower. Fig. 3 shows a flat AMR element 100 without a preferred magnetic orientation. The flat AMR element 100 is formed of a circular Permalloy (AMR) layer, wherein the corresponding electrodes, namely the supply terminal 10, the positive tapping electrode 20, the reference terminal 12 and the negative tapping electrode 22 are arranged on the circular Permalloy (AMR) layer in each case offset with respect to one another by ninety degrees in the counterclockwise direction. The amplitude of the output signals of the AMR element 100 shown in Fig. 3 is 11.5 mV/V and is thus approximately a fifth higher than the amplitude of the output signals of the AMR element 100 shown in Fig. 1 (cf. Fig. 2). The present invention also includes the possibility - of combining a number of AMR sensor elements 100, 110 (cf. Fig. 4) or - of using more than two electrodes 20, 22, 24, 26 to tap differential voltages (cf. Fig. 6). Fig. 4 shows an example of embodiment of a contactless angle measurement system 400 which has an example of embodiment of an angle sensor 200. The angle sensor 200 has a first AMR sensor element 100 and a second AMR sensor element 110, wherein these two sensor elements 100, 110 are rotated by a certain angle, namely by 45 degrees, with respect to one another. In such an arrangement, the output signals 210, 212 and 214, 216 of the AMR sensor elements 100 and 110 exhibit a phase offset by ninety degrees with respect to one another since the output signals 210, 212 of the AMR sensor element 100 are proportional to sin2α and the output signals 214, 216 of the AMR sensor element 110 rotated by 45 degrees are proportional to cos2α. Such an arrangement of the sensor elements 100, 110 thus makes it possible to detect an angle range of 180 degrees (cf. Fig. 5). In Fig. 5, the angle α of the external field H_ext is plotted on the abscissa and the standardized differential output voltage V_out of the AMR elements 100, 110 shown in Fig. 4 is plotted on the ordinate. The angle measurement system 400 has, in addition to the angle sensor 200, an integrated circuit 300 for evaluating the output signals 210, 212 and 214, 216 of the sensor elements 100 and 110; this circuit arrangement 300 in turn has - a first analog/digital converter 320 which can be supplied with the output signals 210, 212 of the first sensor element 100 and with the first output signal 312 of an input buffer 310 and - a second analog/digital converter 330 which can be supplied with the output signals 214, 216 of the second sensor element 110 and with the second output signal 314 of the input buffer 310. In order to determine the angle αl or α2 from the first output signals 322 and 332 of the analog/digital converters 320 and 330, the integrated circuit 300 furthermore has an arithmetic unit 340 which is arranged downstream of the two analog/digital converters 320, 330. Moreover, in order to adapt the characteristic of the curve that is to be output, an adaptation unit 350 is provided which can be supplied with the second output signals 324 and 334 of the analog/digital converters 320 and 330 and with the output signal 342 of the arithmetic unit 340, said adaptation unit being connected between the arithmetic unit 340 and a digital/analog converter 360. This digital/analog converter 360 which is likewise assigned to the integrated circuit 300 can be supplied with the output signal 352 of the adaptation unit 350. In order to buffer-store the output signal 372 of the integrated circuit 300, an output buffer 370 is provided which can be supplied with the output signal 362 of the digital/analog converter 360. Finally, the integrated circuit arrangement 300 has - an oscillator/clock generator unit 380, - a test/trim unit 382 which is provided to test and/or compare the determined values and - a reset unit 384. Fig. 6 shows a third example of embodiment of a magnetoresistive sensor element 100. This flat AMR element 100 is designed to be circular and has a total of four tapping electrodes 20, 22 and 24, 26 for tapping differential voltages V_outi an V_out2, respectively. The first, positive tapping electrode 20 and the second, negative tapping electrode 22 are arranged opposite one another and are offset by in each case ninety degrees - to the supply terminal 10 assigned to the tapping electrodes 20, 22 and - to the reference terminal 12 assigned to the tapping electrodes 20, 22.

A first supply voltage VCC1 is applied to the AMR element 100 against ground potential GND1 by means of the supply electrode 10 and the reference terminal 12. The third, positive tapping electrode 24 and the fourth, negative tapping electrode 26 are likewise arranged opposite one another and are offset by in each case ninety degrees - to the supply terminal 14 assigned to the tapping electrodes 24, 26 and - to the reference terminal 16 assigned to the tapping electrodes 24, 26.

A second supply voltage VCC2 is applied to the AMR element 100 against ground potential GND2 by means of the supply electrode 14 and the reference terminal 16. The third tapping electrode 24 is thus the first tapping electrode with respect to the supply voltage VCC2 or to the current flow i2; the fourth tapping electrode 26 is thus the second tapping electrode with respect to the supply voltage VCC2 or to the current flow i2. The electrodes 14, 16 and 24, 26 are in each case arranged offset by 45 degrees in the clockwise direction to the electrodes 10, 12 and 20, 22. The third example of embodiment shown in Fig. 6 thus corresponds approximately to an integrated embodiment of the angle sensor 200 shown in Fig. 4. (In the angle sensor 200 shown in Fig. 4, the electrodes 14, 16 and 24, 26 are assigned to the second sensor element 110, wherein the second sensor element 110 is rotated by 45 degrees in the clockwise direction with respect to the first sensor element 100 having the electrodes 10, 12 and 20, 22.) On account of the described arrangement of the electrodes of the flat sensor element 100 shown in Fig. 6, a comparable technical effect as in the case of the angle sensor 200 shown in Fig. 4 is achieved, that is to say the output signals V_outι, V_out2 tapped by the tapping electrodes 20, 22 and 24, 26 exhibit a phase shift comparable to Fig. 5. In order to illustrate the differences between the above-described invention and the prior art, a known angle sensor in the form of a so-called double bridge is shown in Fig. 7A. This angle sensor has two Wheatstone bridges which are offset by 45 degrees with respect to one another, wherein - the resistors Rla, Rib, Rlc and Rid of the first Wheatstone bridge and - the resistors R2a, R2b, R2c and R2d of the second Wheatstone bridge are associated. The circuit arrangement of such a Wheatstone bridge is shown in Fig. 7B. Besides the four resistors Rla, Rib, Rlc and Rid, the Wheatstone bridge has - a supply terminal for applying the supply voltage VCC, - a grounded reference terminal GND, - a tapping electrode for tapping the negative output signal V- or the negative differential voltage -V_out and - a tapping electrode for tapping the positive output signal V+ or the positive differential voltage +V₀ut-

LIST OF REFERENCES:

100 first magnetoresistive sensor element, in particular first anisotropic magnetoresistive sensor element 110 second magnetoresistive sensor element, in particular second anisotropic magnetoresistive sensor element

10 supply terminal, in particular first supply terminal of the first sensor element 100 12 reference terminal (with respect to the supply terminal 10), in particular first reference terminal (with respect to the first supply terminal 10) of the first sensor element 100, for example at ground potential GND, in particular at first ground potential GND1 14 supply terminal of the second sensor element 110 (cf. second example of embodiment, Fig. 4) or second supply terminal of the first sensor element 100 (cf. third example of embodiment, Fig. 6) 16 reference terminal (with respect to the supply terminal 14) of the second sensor element 110 (cf. second example of embodiment, Fig. 4), for example at ground potential GND, or second reference terminal (with respect to the second supply terminal 14) of the first sensor element 100 (cf. third example of embodiment, Fig. 6), for example at ground potential GND2 20 first, in particular positive, tapping electrode of the first sensor element 100

22 second, in particular negative, tapping electrode (with respect to the first tapping electrode 20) of the first sensor element 100 24 first, in particular positive, tapping electrode of the second sensor element 110 (cf. second example of embodiment, Fig. 4) or third, in particular positive, tapping electrode of the first sensor element 100 (cf. third example of embodiment, Fig. 6) 26 second, in particular negative, tapping electrode (with respect to the first tapping electrode 24) of the second sensor element 110 (cf. second example of embodiment, Fig. 4) or fourth, in particular negative, tapping electrode of the first sensor element 100 (cf. third example of embodiment, Fig. 6) 200 angle sensor

210 first output signal of the angle sensor 200, in particular positive output signal of the first sensor element 100

212 second output signal of the angle sensor 200, in particular negative output signal of the first sensor element 100

214 third output signal of the angle sensor 200, in particular positive output signal of the second sensor element 110

216 fourth output signal of the angle sensor 200, in particular negative output signal of the second sensor element 110 300 circuit arrangement, in particular integrated circuit, for evaluating the output signal 210, 212, 214, 216

310 input buffer

312 first output signal of the input buffer 310

314 second output signal of the input buffer 310 320 first analog/digital converter

322 first output signal of the first analog/digital converter 320

324 second output signal of the first analog/digital converter 320

330 second analog/digital converter

332 first output signal of the second analog/digital converter 330 334 second output signal of the second analog/digital converter 330

340 arithmetic unit

342 output signal of the arithmetic unit 340

350 adaptation unit

352 output signal of the adaptation unit 350 360 digital/analog converter

362 output signal of the digital/analog converter 360

370 output buffer

372 output signal of the angle measurement system 400, in particular output signal of the circuit arrangement 300, specifically output signal of the output buffer 370

380 oscillator/clock generator unit

384 reset unit

400 contactless angle measurement system α angle between the direction D of the drop in the supply voltage VCC or flow of the supply current i and the direction of the resulting magnetic field H_res αl angle between the direction Dl of the drop in the first supply voltage VCCl or flow of the first supply current il and the direction of the resulting magnetic field Hre_s α2 angle between the direction D2 of the drop in the second supply voltage VCC2 or flow of the second supply current i2 and the direction of the resulting magnetic field H_res

D direction of the drop in the supply voltage VCC or flow of the supply current i Dl direction of the drop in the first supply voltage VCCl or flow of the first supply current il

D2 direction of the drop in the second supply voltage VCC2 or flow of the second supply current i2

GND reference potential, in particular ground potential GND1 first reference potential, in particular first ground potential GND2 second reference potential, in particular second ground potential Ho intrinsic magnetization, in particular intrinsic magnetic field

Hext external magnetic field Wres resulting internal magnetic field i supply current il first supply current i2 second supply current

VCC = Vcc supply voltage, in particular against ground potential GND

VCCl first supply voltage, in particular against ground potential GND1

VCC2 second supply voltage, in particular against ground potential GND2

Vout voltage difference or differential voltage

Voutl first voltage difference or first differential voltage V_out2 second voltage difference or second differential voltage V+ in particular positive differential voltage V_out to be tapped at the first tapping electrode 20

V+l in particular positive differential voltage V_outι to be tapped at the first tapping electrode 20 V-l in particular negative differential voltage V_outi to be tapped at the second tapping electrode 22 V+2 in particular positive differential voltage V_out2 to be tapped at the first tapping electrode 24 (cf. second example of embodiment, Fig. 4) or at the third tapping electrode 24 (cf. third example of embodiment, Fig. 6) V-2 in particular negative differential voltage V_out2 to be tapped at the second tapping electrode 26 (cf. second example of embodiment, Fig. 4) or at the fourth tapping electrode 26 (cf. third example of embodiment, Fig. 6)

Claims

CLAIMS:

1. A magnetoresistive sensor element (100, 110) which - by means of at least one supply terminal (10, 14), in particular by means of at least a first supply terminal, and - by means of at least one reference terminal (12, 16), in particular by means of at least a second supply terminal, for example at ground potential (GND; GNDl, GND2) can be supplied with at least one supply voltage (VCC; VCCl, VCC2) and with at least one supply current (i; il, i2), respectively, - wherein the differential voltage (V_out; V_outι, V_out ) which is set as a function of the angle (α; αl, α2) — between the direction (D; Dl, D2) of the drop in the supply voltage (VCC;

VCCl, VCC2) or flow of the supply current (i; il, i2) - and the direction of the resulting internal magnetic field (H_res) can be tapped between at least a first, in particular positive (V+; V+l, V+2), tapping electrode (20, 24) and at least a second, in particular negative (V-; V-1, V-2), tapping electrode (22, 26) and - wherein the direction of the resulting internal magnetic field (H_res) is given by superposing the intrinsic magnetization (Ho) and at least one external magnetic field characterized in that the magnetoresistive sensor element (100, 110) is designed to be flat, in particular the drop in the supply voltage (VCC; VCCl, VCC2) is continuous.

2. A sensor element as claimed in claim 1, characterized in that the resulting internal magnetization (H_res) is aligned essentially parallel to the external magnetic field (H_ext).

3. A sensor element as claimed in claim 1 or 2, characterized in that the direction of the gradient of the differential voltage (V_out; V_outι, V_out₂) is oriented essentially perpendicular to the direction (D; Dl, D2) of the drop in the supply voltage (VCC; VCCl, VCC2) or flow of the supply current (i; il, i2).

4. A sensor element as claimed in at least one of claims 1 to 3, characterized in that the sensor element (100, 110) is foraied at least partially of at least one ferromagnetic alloy, for example of Permalloy.

5. A sensor element as claimed in at least one of claims 1 to 4, characterized in that the sensor element (100, 110) - is designed to have four or more poles and/or - is designed to be essentially rectangular or essentially circular and/or - has no preferred magnetic orientation.

6. An angle sensor (200) for measuring magnetic field strengths, in particular the temporal gradient of magnetic field strengths, characterized by at least one sensor element

(100, 110) as claimed in at least one of claims 1 to 5.

7. An angle sensor as claimed in claim 6, characterized in that the direction (D 1) of the drop in the first supply voltage (VCCl) or flow of the first supply current (il) is rotated or offset by a defined angle, for example by about 45 degrees, with respect to the direction (D2) of the drop in the second supply voltage (VCC2) or flow of the second supply current (12).

8. An angle sensor as claimed in claim 7, characterized by the combination - of a first sensor element (100) assigned to the first supply voltage (VCCl) or to the first supply current (il) and - of a second sensor element (110) assigned to the second supply voltage (VCC2) or to the second supply current (i2).

9. An angle sensor as claimed in claim 7, characterized in that the first supply voltage (VCCl) or the first supply current (il) and the second supply voltage (VCC2) or the second supply current (i2) are assigned to one and the same sensor element (100).

10. A contactless angle measurement system (400), characterized by - at least one angle sensor (200) as claimed in at least one of claims 6 to 9 and - at least one circuit arrangement (300), in particular at least one integrated circuit, which can be supplied with at least one output signal (210, 212, 214, 216) of the angle sensor (200) and is provided to evaluate the output signal (210, 212, 214, 216).

11. An angle measurement system as claimed in claim 10, characterized in that the circuit arrangement (300) has: - at least a first analog/digital converter (320) which can be supplied ~ with the at least one, in particular first, output signal (210, 212) of the, in particular first, sensor element ( 100) and ~ with at least a first output signal (312) of at least one input buffer (310), - at least one further analog/digital converter (330) which can be supplied - with the at least one output signal (214, 216) of the second sensor element (110) or with the at least one, in particular second, output signal (214, 216) of the, in particular first, sensor element (100) and ~ with at least a second output signal (314) of the input buffer (310), - at least one arithmetic unit (340) which can be supplied ~ with at least a first output signal (322) of the first analog/digital converter (320) and — with at least a first output signal (332) of the further analog/digital converter

(330), said arithmetic unit being provided to determine at least one value, in particular at least one angle (α; αl, α2), from the first output signals (322 and 332) of the analog/digital converters (320 and 330) by means of at least one algorithm, for example by means of the Cordic algorithm, - at least one adaptation unit (350) which can be supplied with the second output signals (324 and 334) of the analog/digital converters (320 and 330) and with the output signal (342) of the arithmetic unit (340), said adaptation unit being provided in particular to adapt the characteristic of the curve that is to be output, - at least one digital/analog converter (360) which can be supplied with the output signal (352) of the adaptation unit (350) and - at least one output buffer (370) which can be supplied with the output signal (362) of the digital/analog converter (360) and is provided in particular to buffer-store the output signal (372) and/or - at least one oscillator/clock generator unit (380) and/or - at least one test/trim unit (382) which is provided in particular to test and/or compare the determined values and/or - at least one reset unit (384).

12. The use of at least one sensor element (100, 110) as claimed in at least one of claims 1 to 5 and/or of at least one angle sensor (200) as claimed in at least one of claims 6 to 9 and/or of at least one angle measurement system (400) as claimed in claim 10 or 11 - for detecting at least one reference mark when measuring at least one crankshaft angle, - for detecting metallic objects, - for measuring rotation speeds and/or currents, - for detecting weak magnetic fields, for example for detecting small movements and/or changes in active components of cars or machines, such as for example of at least one drive, of at least one metal rod, of at least one cam, of at least one wheel or of at least one gearwheel, - for detecting and/or controlling traffic movements, - for navigation purposes, for example using at least one compass, or - for contactless angle measurement.