DE102017123772B4 - Electromagnetic measuring system for the detection of length and angle based on the magneto-impedance effect - Google Patents

Abstract

A measurement arrangement for measuring the distance or angle with a scale (1) with magnetization varying along a measuring direction (x), which effects a correspondingly varying magnetic field (B), and at least one scanning head (2) which depends on the relative position to scale (1) in the measuring direction (x) of the varying magnetic field (B) is penetrated and comprising: at least one ferromagnetic film (6) due to the magnetoimpedance effect dependent on the magnetic field (B) and along the measuring direction (x) varying local a signal source, which is designed to feed an alternating current into the at least one foil (6) so that it flows transversely to the measuring direction (x), at least one sensor unit (3), which is adapted to at least two phase-shifted sensor signals (U, U), which depend on the local electrical impedance of the at least one film (6)

Description

TECHNICAL AREA

The embodiments described herein relate to a novel position sensing electromagnetic measuring device based on the physical effect of "Giant Magneto Impedance" (GMI).

BACKGROUND

Measuring devices for length and angle detection are known and work according to different physical principles. Furthermore, a comparison of the main features of these measuring systems is made:

Optoelectronic measuring systems have a very short measuring period (period of division of the encoder) and are therefore very accurate, but have a very high sensitivity to mechanical stress (shock, vibration) and pollution.

Magnetic measuring systems have a longer measuring period, are robust against environmental influences, have large scanning distances (air gap between scanning head and scale), but have - due to comparatively large interpolation errors caused by the small sensing surface of the magnetic sensors and single period scanning paired with the inhomogeneity of the magnet strengths from period to period and have a significant inversion error (hysteresis, when changing the direction of movement produces a signal jump) - a lower accuracy.

Inductive measuring systems have similar measuring periods as the magnetic measuring systems, have a higher accuracy and have no hysteresis. The scanning distance is very low in relation to the magnetic measuring systems and thus limits the respective application.

mit:

• - „δ“ - Skin-Eindringstiefe,
• - „f“ - Arbeitsfrequenz,
• - „µ“ - magnetische Permeabilität,
• - „σ“ - elektrische Leitfähigkeit,

The physical magneto-impedance effect is known per se and finds applications in sensors of various types. The magneto-impedance effect causes a ferromagnetic or soft magnetic foil (wire), which is traversed by a high-frequency current, its (its) impedance in dependence on an external electromagnetic field changes. This behavior can be explained with the skin effect known per se as follows: $$\delta =\frac{1}{\sqrt{\pi f\mu \sigma }}$$

With:

• - "δ" - skin penetration,
• - "f" - working frequency,
• - "μ" - magnetic permeability,
• - "σ" - electrical conductivity,

The skin penetration depth δ of the currents flowing through the material may change for a particular material either with the frequency of these currents and / or with the magnetic permeability of the material. The 1 symbolically shows these dependencies, where B denotes the magnetic induction (flux density), H the magnetic field strength and Z the impedance.

aufweist.An external magnetic field can change the magnetic permeability of a ferromagnetic metal foil by a factor of 10 ^N (where N> 2). That is, the magneto-impedance effect has a very high impedance / reluctance change $\left(\frac{\mathrm{\Delta }X}{X_0}\right)\times 100\%$

having.

If one compares the penetration depth δ for a material which is under the influence of two electromagnetic fields of field strength H ₁ and H ₂ in two different regions, one obtains for the ratio δ ₁ / δ _{2 of} the respective penetration depths: $$\frac{{\mathrm{<figure-callout\; id="1"\; label="\delta "\; filenames="DE102017123772B4\_0012.png,DE102017123772B4\_0013.png"\; state="\{\{state\}\}">\delta </figure-callout>}}_1}{{\mathrm{<figure-callout\; id="2"\; label="\delta "\; filenames="DE102017123772B4\_0012.png,DE102017123772B4\_0013.png"\; state="\{\{state\}\}">\delta </figure-callout>}}_2}=\frac{\sqrt{\mathrm{<figure-callout\; id="2"\; label="\pi \; f\; \mu "\; filenames="DE102017123772B4\_0012.png,DE102017123772B4\_0013.png"\; state="\{\{state\}\}">\pi \; </figure-callout>}f{\mu }_{}{}_2\sigma }}{\sqrt{\mathrm{<figure-callout\; id="1"\; label="\pi \; f\; \mu "\; filenames="DE102017123772B4\_0012.png,DE102017123772B4\_0013.png"\; state="\{\{state\}\}">\pi \; </figure-callout>}f{\mu }_{}{}_1\sigma }}=\sqrt{\frac{{\mathrm{<figure-callout\; id="2"\; label="\mu "\; filenames="DE102017123772B4\_0012.png,DE102017123772B4\_0013.png"\; state="\{\{state\}\}">\mu </figure-callout>}}_2}{{\mathrm{<figure-callout\; id="1"\; label="\mu "\; filenames="DE102017123772B4\_0012.png,DE102017123772B4\_0013.png"\; state="\{\{state\}\}">\mu </figure-callout>}}_1}}>{10}^{N/2}.\text{where N}>\mathrm{Second}$$

Since the impedance Z is in principle inversely proportional to the penetration depth δ, the following is obtained for the ratio Z ₂ / Z _{1 of} the impedances: $$Z~\frac{1}{\delta }\to \frac{Z_2}{{\mathrm{<figure-callout\; id="1"\; label="Z"\; filenames="DE102017123772B4\_0012.png,DE102017123772B4\_0013.png"\; state="\{\{state\}\}">Z</figure-callout>}}_1}>{10}^{N\text{/}2}.\text{where N}>\mathrm{Second}$$

This high sensitivity characterizes the Magnetoimpedanceffekt and leads in their applications to high signal contrast and further to very good efficiencies.

Below are some examples of gauges that take advantage of the GMI effect. From the patent US7791331-B2 a length measuring device is known which has two meander-shaped turns of a ferromagnetic alloy and a movable single magnet. Due to the triangular geometry of these windings, which are traversed by a high-frequency current, a variation of their impedance arises depending on the relative position of the magnet. This device is limited in its measuring range versus the position resolution and accuracy that can be achieved.

From the patent DE19953190-C2 An angle encoder is known. It consists of a star-shaped conductor with a planar geometry created from a ferromagnetic alloy and a permanent magnet that can rotate about its axis relative to this conductor. This type of encoder can not detect the direction of rotation (only the rotation speed) and has a very small number of pulses per revolution (resolution).

A manual reading head based on the GMI effect for reading magnetically encoded tapes is disclosed in the specification AT406715-B known. This device can read only the magnetic pattern from the tape and is not designed for length determination.

The inductive length and angle measuring system described in the patent EP1164358-B1 Known on the market under the name AMOSIN® achieves higher accuracies and resolution in sub-micron range and also has no hysteresis. However, it has the disadvantage that the scanning distance between scale and scanning head is approximately twice less than for the measuring device presented here for the same length of the graduation period. In addition, the sensor of the here presented in the newly introduced measuring device is very simple, has a much higher sensitivity and has higher signal amplitudes.

The publication DE 10 2004 017 191 A1 relates to an electromagnetic device for determining the direction of movement of a sensor object by the simultaneous detection of two orthogonal magnetic field components. In this publication it is described that for this detection - among other things - also integrated sensors, which are based on the known physical principle of the Giant Magneto Impedance (GMI), can be used. However, in no way is a precise position detection and sensor array specified.

The patent EP 2 378 253 B1 describes the specific geometry of a magnetic coding of a scale for the coarse (resolution in the range of about 1 mm) absolute position detection. It is mentioned here that also sensors working on the GMI principle can be used. This measuring arrangement can not be used for measuring systems which are to determine a comparatively accurate (<1 μm) relative position between two mutually movable machine components.

The patent US 6,239,594 B1 For certain compositions, ferromagnetic alloys can be used for various applications, including GMI devices.

The publication DE 10 2014 201 975 A1 relates to a GMI measuring arrangement for the distance detection (proximity sensor / switch) in small measuring ranges perpendicular to the sensor plane. This arrangement is not suitable for position detection for measuring the displacement of a scale. The publication EP 1 164 358 B1 finally shows an example of an inductive length measuring system.

The inventors have set themselves the task of providing a measuring device for lengths or angles, which makes use of the magneto-impedance effect and allows high accuracy and relatively large scanning distances, without being affected by the undesirable phenomenon of hysteresis. Furthermore, low manufacturing costs of the sensors are desirable and a flexible sensor carrier. It is further desirable to have a large scanning area over several periods of the magnetic scale, thereby achieving good signal averaging and high registration.

SUMMARY

The mentioned object is achieved by a measuring device according to claim 1 and by a method according to claim 10. Various embodiments and further developments are the subject of the dependent claims.

list of figures

• 1 zeigt ein B/H Diagramm.
• 2 illustriert die Hauptkomponenten der hier beschriebenen Ausführungsbeispiele.
• 3 illustriert ein erstes Ausführungsbeispiel eines Messsystems zur Messung von Weg oder Winkel.
• 4 illustriert ein exemplarisches Beispiel einer elektronischen Schaltung für die Signalauswertung.
• 5 illustriert ein zweites Ausführungsbeispiel eines Messsystems zur Messung von Weg oder Winkel.
• 6 illustriert ein drittes Ausführungsbeispiel eines Messsystems zur Messung von Weg oder Winkel.
• 7 illustriert ein viertes Ausführungsbeispiel eines Messsystems, das für die Winkelmessung geeignet ist.
• 8 illustriert ein Beispiel eines magnetischen Maßstabs für ein Messsystem zur Messung der Absolutposition.

Various exemplary embodiments are explained in more detail below with reference to figures. The illustrations are not necessarily to scale and the invention is not limited to the aspects presented. Rather, it is important to present the underlying principles:

• 1 shows a B / H chart.
• 2 illustrates the major components of the embodiments described herein.
• 3 illustrates a first embodiment of a measuring system for measuring path or angle.
• 4 illustrates an exemplary example of an electronic circuit for signal evaluation.
• 5 illustrates a second embodiment of a measuring system for measuring path or angle.
• 6 illustrates a third embodiment of a measuring system for measuring path or angle.
• 7 illustrates a fourth embodiment of a measuring system that is suitable for angle measurement.
• 8th illustrates an example of a magnetic scale for a measurement system for measuring the absolute position.

DETAILED DESCRIPTION

The embodiments described here (see 2 ) comprise a magnetic scale 1 with hard magnetic division with alternating north and south poles with the same or different pole lengths and a scanning head 2 , which is a planar sensor unit 3 and an electronic evaluation system 4 having. The sensor unit 3 includes a ferromagnetic foil 6 (see. 3 . 5 and 6 ).

These two main components of the measuring device (scale 1 and readhead 2 ) are arranged with an air gap "d" to each other and mechanically coupled to two machine elements that can move relative to each other linear or rotary and their relative or absolute position (linear position or angular position) is detected.

The division of the scale caused by the magnetic fields generated by him in the scanning head 2 arranged ferromagnetic film, the formation of corresponding regions of higher and lower permeability and consequently also higher or lower impedance. This position-dependent impedance variation is detected by means of one or more sensor elements and output as position information after the electronic processing of the sensor signals generated by the sensor elements in the evaluation electronics.

2 illustrates an embodiment of a measurement system that is capable of measuring positions (path or angle) using the GMI effect. The measuring system shown comprises a scale realized as a thin strip 1 which, by magnetizing a hard-magnetic layer, has alternating polarities (North N, South S), which for the sake of simplicity are shown below periodically (which need not necessarily be the case). In essence, the scale is a permanent magnet with alternating polarization. The magnetic field generated by the permanent magnet is position-dependent and varies, for example, periodically with the pitch of the scale 1 ,

The measuring system further comprises a scanning head 2 comprising a magnetic impedance sensor built on a thin, flexible substrate (further as a sensor unit 3 referred to) and an electronic evaluation 4 which is adapted to the sensor signals of the sensor unit 3 to process and this in a relative position information of the scanning head (relative to the scale 1 in measuring direction "x"). The scan is made contactless with a distance "d" (air gap) between scale 1 and readhead 2 ,

The functioning of the measuring device according to the example of 2 is based on the diagram in 3 explained in more detail. According to the in 3 illustrated embodiment, the sensor unit comprises 3 a flexible, non-magnetic substrate 5 on which single thin sheets 6 (In the example shown four pieces) of a ferromagnetic material in a particular arrangement and are applied electrically separated from another. The slides 6 are also referred to below as sensor elements.

In the example shown, the ferromagnetic films 6 (Sensor elements) within a pair of two sensor elements a distance of about λ / 2, where 2 · λ, the (magnetic) graduation period of the scale 1 is. The length of a sensor element corresponds approximately to the magnetic width of the scale 1 transverse to measuring direction. A first pair of slides 6 that are labeled S + and S- are associated with a sine channel, whereas a second pair of slides 6 , which are labeled C + and C-, are assigned to a cosine channel. The two pairs of films (S +, S- and C +, C-) are at a distance of about n · λ + λ / 4 on the substrate 5 arranged, where n is an integer.

In a specific embodiment, a plurality of first pairs of foils may also be assigned to the sine channel and a plurality of second pairs of foils may be assigned to the cosine channel. Two pairs of foils associated with the sine (or cosine) channel are spaced n · λ apart, whereas two pairs of foils, as noted, are spaced approximately n · λ + λ / 4 when associated with different channels.

The film thickness of the films 6 may range between approximately 5 μm and 30 μm, depending on how the measuring system is designed and depending on material properties, working frequency, graduation period, etc.

For the sake of simplicity, is in 3 only a minimum number of sensor elements shown. It can be used for signal acquisition and averaging of technological (eg geometric) errors in the Sensor and scale to be advantageous in that - as already mentioned - several pairs of sensor elements along the measuring direction "x" at a distance of η · λ are arranged repeatedly to another, and the sensor signals of the sensor elements 6 for each of the two measurement channels (sine and cosine) are summed.

According to the example in 4 has the in the scanning head 3 arranged evaluation 4 a signal generator 41 configured to generate high frequency (in the range of 1 MHz to about 100 MHz) carrier currents of constant amplitude. Each of the four illustrated sensor elements 6 (labeled S +, S-, C +, C-) is electrically connected to the signal generator so as to be traversed by the carrier current i. In the examples presented here are the sensor elements 6 connected in series, so that the same carrier current i through the sensor elements 6 flows.

The in the sensor unit 2 arranged sensor elements 6 (Slides) are from the scale 1 generated magnetic field (magnetic flux density B) interspersed. As mentioned, the magnetic field varies according to the pitch of the scale along the measuring direction (x-direction), and thus the local magnetic field strength / flux density in the sensor elements depends 6 from the relative position between the sensor unit 2 and scale 1 from. With a shift of the scale relative to the sensor unit, the magnetic field shifts accordingly.

As already explained, the magnetoimpedance effect (GMI effect) causes the relative permeability in each of the sensor elements / foils, depending on the size of the magnetic flux density B 6 changes and consequently also the current penetration depth (skin effect) of the high-frequency exciter currents and thus also the impedance of the sensor elements / foils 6 , The measurement of the impedances of the four sensor elements / films 6 using the evaluation electronics 4 reflects the dependence of these impedances on the relative position of the scanning head 2 to the scale 1 contrary. As mentioned, the sensor elements / foils 6 fed with a constant current i and the resulting voltages U _S + . U _S - and U _C + . U _C - (voltage drops across the sensor elements 6 ) be evaluated.

In order to achieve high immunity to interference and to suppress unwanted signal offset and noise, the detection of the signals (eg voltages U _S + . U _S - and U _C + . U _C -) of the sensor elements 6 in a differential manner such that a sinusoidal signal ( U _S ) by the formation of the voltage difference U _S + - U _S - and a cosine signal ( U _C ) by the formation of the voltage difference U _C + - U _C - Is determined (eg by means of differential amplifier 42 and 43 ). The difference signals U _S and U _C (Sine and cosine signal) have the same frequency as the high-frequency carrier current i. The signals U _S and U _C will be in the example 4 demodulated (demodulator 44 ). The result of the demodulation is a DC voltage whose level is at a uniform movement of the scale 1 relative to the scanning head 2 varies approximately sinusoidally or cosinusoidally. With a view to a simple presentation, the in 3 and 4 In the following examples, the two signals sin α and cosa shifted in phase by about 90 ° after demodulation are shown 44 represents the high-frequency carrier wave.

The design of an electronic circuit that amplifies the sensor signals converts and in the known standardized interfaces at the output of the scanning head 2 the downstream electronics for position indicators or drive control is available, is known per se and is therefore not further explained; but of importance is the fact that the generation of two phase-shifted sinusoidal signals, the unique direction of movement and the electrical angle can be clearly determined within a period.

• - I₀ - konstante Stromamplitude,
• - i - Trägerstrom,
• - ω = 2πf, f- konstante Frequenz,
• - x - relative Lage Maßstab 1 zur Sensoreinheit 3,
• - λ - Hälfte der magnetischenTeilungsperiode,
• - k - natürliche Zahl,
• - U_S+ , U_S- , U_C+ , U_C- - Teilspannungen,
• - U_k - konstante Übertragungsspannung,
• - U_OS , U_OC - konstante Offsetspannungen,
• - $\alpha =\frac{2\pi }{\lambda }x$
  
  - elektrischer Winkel,

und i = I₀sinωt
ergibt sich: $$U_{S+}=U_k\left(U_{OS}+sin\left(\frac{2\pi }{\lambda }x+2k\pi \right)\right)sin\omega t,$$

und $$U_{S-}=U_k\left(U_{OS}+sin\left(\frac{2\pi }{\lambda }x+\pi +2k\pi \right)\right)sin\omega t,$$

und in ähnlicher Weise: $$U_{C+}=U_k\left(U_{OC}+sin\left(\frac{2\pi }{\lambda }x+\frac{\pi }{4}+2k\pi \right)\right)sin\omega t,$$

und $$U_{C-}=U_k\left(U_{OS}+sin\left(\frac{2\pi }{\lambda }x+\frac{\pi }{4}+2k\pi \right)\right)sin\omega t,$$

und nach der Differenzbildung (Operationsverstärker 43) für jeden der zwei Messkanäle (Sinus- und Cosinuskanal): $$U_S=U_{S+}-U_{S-}=U_{k}sin\alpha sin\omega t$$

$$U_C=U_{C+}-U_{C-}=U_{k}cos\alpha sin\omega t$$

As already mentioned, the four ferromagnetic films (sensor elements 6 ) in the sensor unit 3 relative to the magnetic scale 1 move. These sensor elements 6 are traversed by a constant in frequency and amplitude current (carrier current i), of the in the evaluation electronics 4 located power source 41 is produced. The voltage drop (see 4 , Tensions U _S + . U _S - and U _C + . U _C -) above each of the four sensor elements 6 can be considered as a measure of the impedance of the respective film. These voltages U _S +, U _S - and U _C + . U _C - be from the differential amplifiers 42 provided with the parameters:

• - I ₀ - constant current amplitude,
• - i - carrier current,
• - ω = 2πf, f- constant frequency,
• - x - relative position scale 1 to the sensor unit 3 .
• - λ - half of the magnetic division period,
• - k - natural number,
• - U _{S +} . U _S- . U _{C +} . U _C- - partial stresses,
• - U _k - constant transmission voltage,
• - U _OS . U _OC - constant offset voltages,
• - $\alpha =\frac{2\pi }{\lambda }x$
  
  - electrical angle,

and i = I ₀ sinωt
surrendered: $$U_{S+}=U_k\left(U_{OS}+sin\left(\frac{2\pi }{\lambda }x+2k\pi \right)\right)sin\omega t.$$

and $$U_{S-}=U_k\left(U_{OS}+sin\left(\frac{2\pi }{\lambda }x+\pi +2k\pi \right)\right)sin\omega t.$$

and similarly: $$U_{C+}=U_k\left(U_{OC}+sin\left(\frac{2\pi }{\lambda }x+\frac{\mathrm{<figure-callout\; id="4"\; label="\pi "\; filenames="DE102017123772B4\_0012.png,DE102017123772B4\_0013.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{4}+2k\pi \right)\right)sin\omega t.$$

and $$U_{C-}=U_k\left(U_{OS}+sin\left(\frac{2\pi }{\lambda }x+\frac{\mathrm{<figure-callout\; id="4"\; label="\pi "\; filenames="DE102017123772B4\_0012.png,DE102017123772B4\_0013.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{4}+2k\pi \right)\right)sin\omega t.$$

and after difference formation (operational amplifier 43 ) for each of the two measurement channels (sine and cosine channels): $$U_S=U_{S+}-U_{S-}=U_{k}sin\alpha sin\omega t$$

$$U_C=U_{C+}-U_{C-}=U_{k}cOs\alpha sin\omega t$$

With the help of these two "quadrature" voltages can be in a known manner, the electrical angle and the direction of movement using the demodulators 44 , the analog-to-digital converter 45 and further digital processing determined and output as position information "x".

It should be noted here that, unlike inductive measuring systems and due to the fact that the impedance changes only depend on the amount of flux density B, but not on their direction vector, the sensor signal period λ is half the graduation period (2λ) of the scale. This can be of great advantage in the design of a measuring system and allows higher accuracy and resolution.

Furthermore, it should be noted that the high efficiency of the magneto-impedance effect in the embodiments described here leads to higher sine and cosine signal amplitudes and thereby relatively larger air gaps d can be realized, which is why the embodiments shown here are more versatile than known measuring systems.

5 illustrates a second embodiment of the measuring device, wherein in the illustrated example, the sensor unit 3 realized as follows: A ferromagnetic film 6 is so to the signal source 41 (see. 4 ) is connected in that it is traversed in the transverse direction (transverse to the measuring direction x) of the high-frequency carrier current (excitation current) i (i = I ₀ · sin (ot)). The foil 6 has at least two recesses 8th with a width of about λ / 2 at a distance of about n · λ + λ / 4. The local current density in the foil 6 depends on the described magneto-impedance effect. Depending on the scale 1 generated magnetic flux density B arise in the film 6 local areas of different impedance and thus the local current density in the film becomes 6 essentially the local flux density B and thus the division of the scale 1 reflect. This "current image" can be of planar, parallel to the foil 6 arranged receiver coils 10 be detected differentially, so that in a similar manner as in the embodiment according to 3 and 4 the two phase-shifted signals U _S and U _C can be won.

In this embodiment may be on the film recesses 8th may also be waived if system sizing allows this. The receiver coils 10 For example, they can be realized as multilayer printed circuit boards. In a well-known manner, magnetic fields from the receiver coils 10 Also detect other types of sensors such as semiconductor sensors such as Hall sensors or magnetic thin-film sensors such as magnetoresistance (MR), giant magnetoresistance (GMR) or anisotropic magnetoresistance (AMR).

6 illustrates a third embodiment of the measuring device. In this case, the high-frequency carrier current i is no longer directly into the ferromagnetic film as in the preceding examples 6 fed, but in emitter coils 11 that together with the receiver coils 10 a planar coil structure 9 form.

The emitter coils 11 Induce eddy currents in the ferromagnetic film in a known manner 6 , The strength and spatial location (along the measuring direction "x") of these eddy currents depends on the variable magneto-impedance in certain areas of the foil 6 and is inversely proportional to the local magnetic flux density B of the scale 1 generated magnetic field. The receiver coils 10 have essentially the same function as in the previous example 5 and detect in a differential manner the locally variable eddy currents in the immediately opposite regions of the film 6 , This embodiment offers the advantage that the ferromagnetic film can be realized as a passive element and the coil system as a flexible multilayer printed Implemented circuit and thus can be easily connected to the evaluation electronics.

As already stated, it is advantageous for the position-measuring device that the sensor surface detects several periods of the scale. By the embodiments described here of such a measuring device with flexible film-like sensor units 3 can be realized with a constant air gap d and a measuring device for angle measurement. An exemplary implementation is in 7 shown. The operation is essentially the same as in the already described linear measuring arrangements, the scale 1 is designed as a measuring drum (encoder wheel, multipole wheel) and relative to the scanning head 2 can rotate.

The surface of the scanning head 2 or the sensor unit 3 can be adjusted to any external diameter encoder wheel. In other measuring devices, which have flat, staring sensor elements, this is not readily possible.

In general, the length and angle measuring systems can be classified according to their mode of operation as incremental and absolute measuring systems. Incremental measuring devices have a merely periodically structured scale 1 on, and the position information can be output as counting up or down of measurement pulses after an electrical "reset". In contrast, in the case of an absolutely measuring measuring device, the absolute position of the scale is at any time during the measurement and independently of the preceding signal curve 1 relative to the scanning head 2 to disposal.

In the case of incrementally operating measuring systems, for obtaining one or more "reference pulses", an additional second track running parallel to the periodic main measuring track can be used on the scale 1 be provided. In all described embodiments, this "reference track" can be implemented as any sequence of individual north-south pole pairs. A sensor located in the sensor unit can be realized in the same technique as the sensor elements from the embodiments described above and can detect and output a corresponding reference signal upon detection of the north-south pole pairs.

Furthermore, for each of the exemplary measurement system embodiments described herein, an absolute (lateral or angular) position sensing device may also be implemented (see 8th ).

For an absolute position measurement, the scale has a coding which clearly defines an absolute position and can be realized according to various principles. As an example was in 8th a so-called "random code" Absolutspurausführung shown, where the scale 1 has a sequence of north-south magnetic poles of equal or different lengths, so that a specific combination (code) of length "L" occurs only once in the entire measuring range. Such an absolute track can be detected by any of the embodiments described herein. A uniformly arranged sensor surface consists of differentially operating individual sensor elements and supplies after the signal processing a specific code, eg "1101001", which defines the absolute position at a single point.

To achieve a higher position resolution, it is of course possible to apply an absolute track in parallel to a high-resolution incremental track on the scale and to evaluate it in combination in a known manner.

In the following, some aspects of the embodiments described here will be summarized. The following list is not meant to be exhaustive, but merely exemplary.

Example 1: A measurement arrangement for path or angle measurement with a scale 1 with magnetization varying along a measuring direction x, which causes a correspondingly varying magnetic field B, and with at least one sensor unit 2 penetrated by the magnetic field B and comprising: at least one ferromagnetic film 6 having due to the magneto-impedance effect, a dependent of the magnetic field B and along the measuring direction x varying local electrical impedance; and at least one sensor element (cf., for example 3 . 5 . 6 , Digits 6 . 7 . 10 ), which is designed to generate a sensor signal (eg U _S +, U _S - U _C + . U _C -) to generate the local electrical impedance in a region of the film 6 depends.

Example 2: The measuring device according to Example 1, which further comprises a signal source 41 (see. 4 ), which is adapted to provide an alternating current i, wherein the at least one ferromagnetic film 6 is connected to the signal source, and the alternating current i transverse to the measuring direction x through the at least one ferromagnetic film 6 flows and in operation has a constant frequency and a constant amplitude, and wherein a resulting current density (distribution of the alternating current i) in the at least one ferromagnetic film 6 due to the varying local electrical impedance along the measuring direction x is different.

Example 3: The measuring device according to Example 1, which further comprises a signal source 41 (see. 4 ), which is adapted to provide an alternating current i, in the at least one film 6 is fed, wherein the at least one film 6 comprises at least two foils which are arranged next to one another along the measuring direction x, and wherein the at least one sensor element (cf. 3 , Numeral 6 ) comprises at least two sensor elements S +, S-, C +, C-, which are formed by the films themselves, where as sensor signals U _S + . U _S - U _C + . U _C - In each case a voltage across the measuring direction x is tapped.

Example 4: The measuring device according to Example 1, which further comprises a signal source 41 (see. 4 ), which is adapted to provide an alternating current i, in the at least one film 6 is fed, wherein the at least one sensor element is a magnetic field-sensitive semiconductor sensor element or a magnetic field-sensitive thin-film sensor element which generates a sensor signal as a signal representing a magnetic field strength, of which by the at least one film 6 flowing alternating current is effected.

Example 5: The measuring device according to one of examples 1 to 4, wherein the at least one sensor element is a planar coil (cf. 5 , Do the washing up 10 ) having.

Example 6: The measuring device according to one of Examples 1 to 5, wherein the at least one sensor element comprises a first sensor element S + and a second sensor element S- which are arranged next to one another along the measuring direction, and wherein the sensor signals U _S +, U _S - The first sensor element S + and the second sensor element S- are linked to a difference signal (see. 3 to 6 ).

Example 7: The measuring device according to Example 1, wherein the at least one sensor element at least one planar coil 10 having, wherein the sensor unit 3 at least one emitter coil 11 that is connected to the signal source 41 connected and with the at least one planar coil 10 is coupled transformer (cf. 6 ) and wherein the at least one film 6 acts as an iron core, in which eddy currents are induced, which depends on the local impedance of the at least one foil 6 depend.

Example 8: The measuring device according to one of Examples 1 to 7, wherein the scale 1 a regular division 2 · λ, and wherein the at least one sensor element comprises at least two sensor elements of a first group and at least two sensor elements of a second group, wherein the sensor elements of the first group to each other have a distance corresponding to a multiple of half pitch λ , and wherein the sensor elements of the second group have a spacing relative to the sensor elements of the first group which corresponds to a multiple of half the pitch plus a quarter of the pitch (ie, n * λ + λ / 4).

Example 9: The measuring device according to one of Examples 1 to 8, wherein the scale 1 has several adjacent tracks.

Example 10: The measuring device according to one of examples 1 to 9, wherein the scale has an absolute coding which clearly indicates the position of the scale relative to the sensor unit 2 Are defined.

Example 11. The measuring device according to any one of Examples 1 to 10, wherein the scale has a cylindrical shape and the pitch of the scale is an angular pitch.

Example 12: A method for measuring the relative position between a scale 1 and one of scale 1 spaced sensor unit 2 , According to this example, the method comprises generating a magnetic field varying along a measuring direction x B by means of the scale 1 which has a magnetization varying along the measuring direction, and further influencing the local electrical impedance of at least one foil 6 that in the sensor unit 2 is arranged, wherein the local electrical impedance due to the magneto-impedance effect of the local magnetic field and thus the position of the scale 1 relative to the sensor unit 2 depends. The method further comprises detecting a signal by means of at least one sensor element which determines the local electrical impedance in a region of the at least one foil 6 represents.

Example 13: The method of Example 11, further comprising: feeding a high frequency alternating current into the at least one foil 6 , wherein the current density along the measuring direction x of the local electrical impedance of the at least one film 6 depends, and demodulating the signal detected by the sensor element.

Example 14: The method of Example 13, wherein detecting a signal by means of a sensor element comprises: sensing a voltage across the at least one foil 6 wherein the voltage depends on the local impedance or detecting - by means of a planar coil or a magnetic field-sensitive semiconductor element or thin-film sensor element - a sensor signal representing a magnetic field strength, which differs from that through the at least one foil 6 flowing alternating current is effected.

Example 15. The method of Example 13, wherein the local electrical impedance of the at least one foil 6 through the at least one emitter coil 11 flowing alternating current is influenced, wherein as a sensor element, a planar coil is used, which with the emitter coil 11 is coupled transformer and the at least one slide 6 acts as iron core.

All examples can be used in systems for displacement measurement of displacement or position) as well as for angle measurement (with rotating encoder). Also, with all the examples, depending on the coding of the scale, an incremental (relative) measurement of (angular) positions as well as the measurement of an absolute (angular) position is possible.

Claims (13)

A measurement arrangement for measuring distance or angle with a scale (1) along a measuring direction (x) varying magnetization, which causes a correspondingly varying magnetic field (B), and at least one scanning head (2), which depends on the relative position to scale ( 1) is penetrated in the measuring direction (x) by the varying magnetic field (B) and has the following: at least one ferromagnetic film (6) which, due to the magneto-impedance effect, depends on the magnetic field (B) and along the measuring direction (x) having varying local electrical impedance; a signal source, which is designed to feed an alternating current into the at least one film (6) so that it flows transversely to the measuring direction (x); at least one sensor unit (3) which is designed to generate at least two phase-shifted sensor signals (U _S , U _C ), which depend on the local electrical impedance of the at least one film (6) The measuring arrangement according to Claim 1 having at least two in the measuring direction (x) juxtaposed spaced apart films (6), wherein the alternating current has a constant amplitude and a constant frequency, wherein the films (6) themselves as sensor elements of the sensor unit (3) are formed and wherein the along the measuring direction (x) varying magnetic field (B), which depends on the position of the scale (1) relative to the scanning head (2), the impedance of the films (6) influenced as measurement information (U _S +, U _S -, U _C +, U _C -) is evaluated. The measuring arrangement according to one of Claims 1 and 2 , wherein the local current strengths in the ferromagnetic film (6), which locally vary due to the magnetic field (B), are detected by sensor elements in the form of planar coils (10). A measurement arrangement for measuring distance or angle with a scale (1) along a measuring direction (x) varying magnetization, which causes a correspondingly varying magnetic field (B), and at least one scanning head (2), which depends on the relative position to scale ( 1) is penetrated in the measuring direction (x) by the varying magnetic field (B) and has the following: at least one ferromagnetic film (6) which, due to the magneto-impedance effect, depends on the magnetic field (B) and along the measuring direction (x) having varying local electrical impedance; at least one sensor unit (3), which is designed to generate at least two phase-shifted sensor signals (U _S , U _C ), which depend on the local electrical impedance of the at least one film (6); a signal source configured to provide an alternating current (i), the sensor unit (3) having at least one emitter coil (11) connected to the signal source and transformer coupled to the at least one planar receiver coil (10); the at least one foil (6) acts as an iron core, in which the emitter coil (11) induces eddy currents which depend on the local impedance of the at least one foil (6). The measuring arrangement according to one of Claims 1 to 4 wherein the formation of each of the sensor signals (U _S ) and U _C ) by the difference of two measurement information (U _S +, U _S -; U _C +, U _C -) takes place; wherein the two measurement information (U _{S +} , U _S- , U _{C +} , U _C- ) each of at least one pair of individual sensor elements (S +, S-; C +, C-) are generated, along the measuring direction (x) spaced in the Sensor unit (3) are arranged. The measuring arrangement according to one of Claims 1 to 5 wherein the scale (1) has a regular division with a double period (2 · λ), and wherein the sensor unit (3) comprises at least two sensor elements from a first group and at least two sensor elements from a second group, wherein the sensor elements of the first Group have a distance to each other, which corresponds approximately to an odd multiple of half the period ((2n + 1) · λ / 2) and wherein the sensor elements of the second group have a distance relative to the sensor elements of the first group which corresponds approximately to a multiple of half the period plus a quarter of the period (n · λ + λ / 4). The measuring arrangement according to one of Claims 1 to 6 wherein the scale (1) comprises a plurality of juxtaposed magnetic tracks. The measuring arrangement according to one of Claims 1 to 7 wherein the scale has an absolute coding that uniquely defines the location of the scale relative to the scanning head (2). The measuring arrangement according to one of Claims 1 to 8th wherein the scale has a cylindrical shape and the pitch of the scale is an angular pitch. A method of measuring the relative position between a scale (1) and a scanning head (2) spaced from the scale (1); the method comprises: Generating a magnetic field (B) varying along a measuring direction (x) by means of the scale (1), which has a magnetization varying along the measuring direction (x); Influencing the local electrical impedance of at least one film (6) which is arranged in the sensor unit (3), wherein the local electrical impedance due to the magneto-impedance effect of the local magnetic field and thus of the position of the scale (1) relative to the sensor unit ( 3), and wherein the sensor unit (3) generates at least two phase shifted measurement signals; Detecting a signal by means of at least one sensor element, which represents the local electrical impedance in a region of the at least one film (6); and Feeding an alternating current into the at least one film (6) transversely to the measuring direction (x) or inducing eddy currents, by at least one emitter coil (11), wherein the current distribution depends on the local electrical impedance of the at least one foil (6). The method according to Claim 10 , which further comprises: evaluating, in particular demodulating, the signal detected by means of the sensor element. The method according to Claim 10 or 11 wherein detecting a signal by means of a sensor element comprises: sensing a voltage across the at least one foil (6), the voltage depending on the local impedance, or detecting, by means of a planar coil or a magnetic field sensitive semiconductor element or thin film sensor element, a sensor signal representing a represents magnetic field strength, which is caused by the at least one film (6) locally flowing alternating current. The method according to Claim 12 in that a planar receiver coil (10) is used as the sensor element, which is transformer-coupled to the emitter coil (11) and the at least one ferromagnetic foil (6) acts as an iron core.

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