EP1157394B1 - System for writing magnetic scales - Google Patents

Abstract

The invention relates to a system for pulse magnetizing high-precision magnetic scales. The system comprises a shaped current conductor (1) and a pulse current source (2) that is composed of a capacitor bank (3), a transfer switch (4) and a control unit (5). The compact set-up of the system is the prerequisite for a power circuit that has such a low resistance that the required high pulse currents are obtained at supply voltages of below 60 V. The transfer switch is an H bridge with four switches (7) that contain equal numbers of MOS transistors connected in parallel. The short pulse times that are achieved using the MOS transistors allow the use of shaped current conductors with which magnetized areas can be produced with a very high precision. The inventive system provides a means for saving components, electric power and time by a factor of up to 100.

Description

The present invention relates to an arrangement for what is referred to as writing, in time Sequential section-by-section magnetization of magnetic scales. Magnetic scales are required for length, angle and position determination. They can be done with divisions that exist periodically or in sections magnetized in the opposite direction according to different codes his. Magnetic scales can be linear or circular or any have other shapes. They can be made entirely of hard magnetic material or of hard magnetic material, which is based on a soft magnetic or non-magnetic Carrier located. The surface can be protected by a cover layer.

Arrangements for writing magnetic scales according to two different principles are known. In the first principle (e.g. published patent application DE 41 08 923 A1) a electrical conductor shaped and in the immediate vicinity of the magnetic scale brought that a pulse current flowing through it generates a magnetic field that over extends the full scale or at least a substantial portion thereof and one has such spatial distribution and strength that the magnetization in the form of provided magnetic pattern is set. A disadvantage of this method of Magnetization of magnetic scales is that at the position of the parts of the molded extremely high accuracy requirements must be placed on the electrical conductor go beyond the accuracy requirements of the magnetic scale, because the Transfer of the intended magnetic pattern is not possible without errors. The Shaped electrical conductor is the product of a mechanical manufacture, so that position errors of the scale thus produced cannot be achieved in the range of a few micrometers.

The magnetization of the scale takes place in sections that span several areas magnetization to be set, there is an additional accuracy problem at the interfaces of two successively magnetized sections. The poor accuracy results less from the error of the measured positions of the shaped electrical conductor than from the fact that magnetic fields with a Strength that goes beyond the coercive field strength of the scale material, even outside of the section that the electrical conductor occupies. This is the yardstick magnetized here too. Because the direction of magnetization that is finally set in the scale material dependent on the previous history due to the magnetic hysteresis areas of faulty magnetization form at the interfaces, which then limit the accuracy of the magnetic scale.

Further disadvantages of this principle result from the structure of the pulse current sources (e.g. B. Offenlegungsschrift, DE 34 21 575 A1) such magnetization devices. These pulse current sources deliver current amplitudes up to about 30 kA, are operated with high voltage, have masses of more than 50 kg and are relatively expensive. Because of The high voltage must have relatively rigid leads between the pulse current source and the molded electrical conductor can be used. These supply lines complicate the accurate positioning because it applies forces and vibrations to the molded electrical conductor transfer. The strong current impulse makes them magnetize generated that briefly develops considerable forces at 30 kA.

The second principle for writing magnetic scales is described in DE 44 42 682. Here a print head consists of one or two by a narrow one Gap separated magnetic poles, which are surrounded by at least one coil. The soft magnetic Magnetic poles can be magnetized to saturation by a current through the coil become. Currents of less than 1 A are sufficient for this, since the number of turns of the Coil can be adjusted accordingly. At the end of the single-pole arrangement or in the Magnetic field strengths then occur near the gap of the two-pole arrangement are sufficient to magnetize the scale material. In the case of the bipolar arrangement the gap is guided directly over the scale to be magnetized. The magnetic field emerges from the soft magnetic material on one side of the gap and on the other side of the gap. In the area of the scale in which the Field strength of the leaked magnetic field above the coercive force of the scale material is a magnetization of the scale in the direction of each existing magnetic field. But this is opposite on both sides of the gap. As the position of the print head advances, magnetic reversal is always required of an already magnetized area. That is why disadvantageous because the size of the magnetized eventually in a certain direction

Range from that generated by the write head and also from that already created by the magnetized scale material caused field strength is determined. Thereby the errors of two magnetization processes are added. This is also why they fall not particularly small because the magnetic field strength that emerges from the print head with increasing distance from the gap and from the soft magnetic poles with relative low gradient decreases. This is how small fluctuations in distance ultimately work in substantial differences in length of the magnetized areas. Seems cheapest still to be the operating case in which the writing head touches the scale surface directly. However, this is for a high accuracy of the scale because of the different Frictional forces when moving the print head against the scale, which leads to errors the set position, also not optimal.

If with a circular scale over full 360 ° alternately long poles with oppositely directed magnetization are to occur when used a printhead with a gap due to the opposite field direction on both Difficulties in any case on the sides of the gap if the initially magnetized Areas after rotation of the circular scale by about 360 ° is reached again. This joint is then always with a large error in the position of the magnetization areas afflicted.

The use of a single magnetic pole with a coil brings an improvement in Field distribution, because the magnetic field component emerging perpendicularly from the surface of the pole has an absolute maximum only in the middle of this area. Because of the relatively small Decrease in magnetic field strength across the field direction and a stronger decrease with the distance from the surface of the pole is also the distance between the surface of the Poles and the scale surface must be adhered to extremely precisely. Required magnetic reversal processes near the edge of the areas of constant magnetization to be generated cannot be excluded. The disadvantages in adhering to the intended position with the practically preferred touch method of operation are also available here.

Another disadvantage of maintaining an exact position compared to the printhead the standard when using soft magnetic, by current in a coil Magnetized magnetic poles is given by the fact that forces between the magnetic poles and the already magnetized areas of the scale exist because of the necessary small distances are of considerable amount.

The object of the invention is to provide an arrangement for writing magnetic scales with high accuracy of the dimensions of the magnetized Ranges and with high repeatability of the magnetization within the magnetized Areas is suitable.

This object is achieved by the arrangement described in the main claim, and advantageous embodiments are described in the subclaims.

The arrangement for writing magnetic scales consists of a molded one Current conductor for generating magnetic fields at the location of the scale and one from a capacitor bank, a switch and a control unit composite pulse current source for both current directions. All components are in a compact unit integrated. Due to the compact design, the entire current path is from the capacitor bank extremely short to the shaped conductor. All components and the connecting lines are mounted in a fixed position to each other, so that forces that affect the position of the shaped conductor could change to the magnetized scale, ineffective stay. The short current path and a large cross-section of the lines between the capacitor bank and molded current conductors guarantee low resistance throughout Circuit. Therefore an operating voltage in the low voltage range is sufficient for Generation of the high current required for magnetization.

A small cross-section, which is only directly on the molded conductor, which the Magnetic field generation serves, is limited, leads because of the short length of the molded Current conductor not to limit current, but is a prerequisite for that The center of the shaped conductor is positioned very close to the surface of the scale can be. This ensures the generation of high magnetic field strengths in the scale material.

Since the dimensions of the shaped conductor to the dimensions of the magnetized Areas are adapted, is always one by the current in the molded conductor such magnetic field distribution produces that two or more magnetic reversal of the Scale material is excluded. For writing scales with periodic Magnetization in which the pole length is significantly smaller than the track width Haimelike current conductor used, the conductor spacing is much larger than that Wire diameter. The field strength of those acting perpendicular to the scale surface The field component is maximal in the area between the centers of the two wires. Approximately An extremely strong field gradient occurs below the center points, because here the changes vertical field component its sign. By a current pulse through this hairpin-like Shaped conductor will become the benchmark in the area below Connection line is located between the centers of the wires, in one and immediately adjacent magnetized in the other direction. Correct the length of the Area under the connecting line of the centers of the wires with the pole length, then there is a change in the magnetization direction once set in the scale material not mandatory. There are only magnetization processes with the same magnetization direction for every area of the scale. This and the high field gradient A high accuracy of the length and the field strength of the poles is guaranteed if the The position of the shaped conductor is set using a correspondingly accurate measuring system has been. This also applies in the event that the shaped conductor is at a distance located above the scale surface to avoid errors caused by frictional forces.

With a greater distance between the two parts of the hairpin-shaped shaped current conductor, it is advantageous to choose a rectangular cross-section in which two or more round wires are arranged. This will result in a higher magnetic field strength and better homogeneity of the magnetic field below the surface of the hairpin-shaped conductor, without reducing the field gradient under the conductor cross section.

If the track width of the scale is only slightly larger than the length of the pole, a rectangular shape is formed Current conductor used. Again, with two or more wires in a rectangular one Cross-section again an advantageous high magnetic field strength and good field homogeneity with high field gradients under the middle of the conductor cross section.

For writing scales whose magnetization runs parallel to the scale surface molded current conductors with a band-shaped cross section are used, where the strip thickness is chosen as small as possible, so that the total current in the least Distance to the scale surface is concentrated and generates high magnetic field strengths. The width of the cross section is adapted to the length of the areas to be magnetized, so that the area is magnetized with a current pulse. The shaped one Current conductors can also consist of a number of wires lying directly next to one another exist, which then together fill the band-shaped cross-section and parallel Flows through. It is advantageous to have the thickness of the cross section on both Edges of the tape to choose larger than in the middle part, or on the edge wires with larger Diameter to be used, as this results in a more homogeneous field distribution in the magnetized area Area is present and the magnetic field strength at the edge of this area falls steeply.

Regardless of the special shape, the shaped conductor is always in a holder fixed so that the forces occurring during the current pulse neither on its shape can still change something in its position relative to the scale. The bracket with the shaped conductor is interchangeable, so that always for writing the respective Scale optimally shaped conductor can be used.

The switch of the pulse current source has the shape of an H-bridge. So that from the Capacitor battery Current pulses in opposite directions with the same amplitude and sent over the same time in the shaped conductor, which is the prerequisite this is because the pole lengths of the opposite direction of magnetization at one periodic scale also match with high accuracy. As a switch in the H-bridge MOS transistors are preferably used, with all switches from one equal number of MOS transistors connected in parallel. So will achieved a sufficiently large total current and the resistance of the parallel MOS transistors in the circuit is not current limiting. It is important that the compact structure the arrangement leads to such low inductances in the circuit that the current through the shaped conductor rises to its maximum value in a few tenths of a microsecond. A signal from the control unit allows the MOS transistors to run for a few microseconds be blocked again after the start of the current pulse, because this time period is sufficient for magnetization. This is very low in comparison with the prior art Pulse duration leads to several advantages of the arrangement according to the invention. An advantage consists in the fact that in the short pulse time the voltage at the capacitor bank only drops by a small amount. So can inexpensive electrolytic capacitors are used, which have a high capacity per volume and thus the compact Support the construction of the entire arrangement and its small expansion. Another The advantage is that the small charge of the capacitor battery removed by the pulse current can be supplied again in the pulse pauses by a low current and so only a low power is required to supply the arrangement. The leaves short pulse time to a high repetition frequency so that high writing speeds are achieved be opposed by the method of positioning the arrangement the scale as limited by the possible pulse repetition frequency. Because of the short Pulse time is only a low electrical output in heat in the shaped conductor implemented. So small cross sections can be used for the current conductor without that thermal destruction is to be feared. Due to the small cross sections allows higher magnetic fields in the range of the scale, because the distance of the currents to Scale surface can be kept very small.

According to the invention, the pulse current source is located in a shield made of highly conductive Metal. The only unshielded part is the bracket with the molded conductor, on which, however, the supply and discharge lines are directly adjacent are led. So that the environment of the arrangement is despite the high currents of disturbing or health-endangering electromagnetic fields.

The arrangements according to the invention are for writing magnetic scales with in Direction of measurement periodically alternating magnetization direction and magnetic scales with magnetization areas, the lengths of which are assigned to a code. When used, the positioning of the shaped conductor is non-contact the surface of the scale is intended to cause friction resulting in position errors excluded between the molded conductor and the scale surface becomes.

Fig. 1: Übersicht der erfindungsgemäßen Anordnung

Fig. 2: Geformter Stromleiter mit Halterung

Fig. 3: Haamadelförmiger Stromleiter

Fig. 4: Querschnitte des haamadelförmigen Stromleiters

Fig. 5: Bandförmiger Stromleiter mit Halterung

Fig.6: Bandförmiger Stromleiter

Fig.7: Querschnitte des bandförmigen Stromleiters

Fig.8: Magnetfeldverlauf.

The invention is explained in more detail below using exemplary embodiments. The following is shown in the accompanying drawings:

Fig. 1: Overview of the arrangement according to the invention

Fig. 2: Shaped conductor with bracket

Fig. 3: Haimelike current conductor

Fig. 4: Cross sections of the hairpin-shaped conductor

Fig. 5: Band-shaped current conductor with holder

Fig. 6: Band-shaped current conductor

Fig. 7: Cross sections of the ribbon-shaped conductor

Fig. 8: Magnetic field course.

An overview of an entire inventive arrangement for writing magnetic Fig. 1 shows scales. It consists of a shaped current conductor 1, which is in the Writing is located near the surface of the scale. Shaped in a pulse current source 2 Current pulses are fed into the shaped conductor and produce it Proximity of magnetic field strengths sufficient to magnetize the scale material are. The pulse current source 2 consists of a capacitor bank 3, a changeover switch 4 and a control unit 5. The structure of the arrangement is designed so that between Capacitor battery 3 and shaped conductor 1 with a minimum line length if possible high wire cross section. This is a very low impedance connection as Prerequisite for high currents with low operating voltage of the capacitor bank 3 guaranteed. The operating voltage is supplied via the contacts 8. The supply voltage and the input data line for the control unit 5 takes place via the connection contacts 9th

The switch 4 has the shape of an H-bridge. There are four switches 7, each consisting of the same number of MOS transistors connected in parallel. This ensures sufficient current portability and a sufficiently low resistance of the switches 7. The particular advantage of using MOS transistors over the thyristors or ignitrons used hitherto is that they can be switched from the conductive back to the blocked state at any time by pulses from the control unit 5. The pulse duration can thus be limited to a few microseconds. This period of time is sufficient to magnetize the scale material in any case. A longer pulse duration has no positive effect on the magnetization due to the decreasing current strength of the pulse. Because of the short pulse time, the capacitor bank 3 is only discharged to a small extent with each individual pulse. Therefore, the capacitor bank 3 is made up of electrolytic capacitors 6 connected in parallel. Voltages in the low voltage range of less than 60 V are sufficient as the operating voltage. Because of this low voltage and the usability of electrolytic capacitors 6, the volume required for the required capacity is particularly low, which accommodates the low impedance of the circuit. Since only a partial discharge of the capacitor bank 3 of about 5% takes place, the operating current is correspondingly low and can be below 500 mA. Furthermore, the thermal load on the shaped conductor is low because of the short pulse duration, so that small cross sections can be used here, which lead to high magnetic field strengths in the area of the scale material. Finally, the short pulse duration enables high pulse repetition frequencies of approximately 50 s ^-1 , which increase the economy of the writing process. The entire pulse current source 2 is located in a metal shield 10 so that, despite the high currents and the short switching times, no health-endangering electromagnetic fields emerge.

The shaped conductor 1 is in shape and dimensions to the magnetic pattern to be written adapted to the scale. Fig.2 shows a hairpin-shaped current conductor 11 with the Supply lines 12 on a holder 13. The hairpin-shaped current conductor 11 is in the holder 13 embedded and glued firmly. The leads 12 are also fixed to the bracket 13 connected and are located directly next to each other. So one is through the Current pulse-related change in position of the hairpin-shaped conductor 11 opposite excluded the scale. Due to the small distance between the two feed lines 12 is not an essential electromagnetic despite the position of the bracket 13 outside the shield 10 Stray field available.

An enlarged representation of the hairpin-shaped current conductor 11 is shown in FIG. 3. The rectangular one Cross section 17 of the current conductor 11 has the linear dimensions 15 and 16. Correspondingly 4 this cross-section 17 of a circular conductor cross-section 17.1, of two circular conductor cross-sections 17.2 or of four circular conductor cross-sections 17.3 are taken. If there are several conductor cross sections, they are from Flows flow in the same direction. This is by connecting the individual hairpin-shaped ones in series Current conductor possible. The drawing with the cross section 17.2 corresponds, for example the shaped current conductor 1 in FIG. 1.

The distance 14 between the two cross sections 17 of the hairpin-shaped current conductor 11 is substantially larger than the dimensions 15, 16 of the cross section 17. For a distance 14 of 1 mm and a wire diameter of 0.3 mm, the field strength in FIG Plane component of the hairpin-shaped current conductor 11 is shown for different distances 24 at a current of 2200 A above the distance from the center of the hairpin-shaped current conductor 11. The curves 21; 22 and 23 are valid for distances 24 of 0.05 mm, 0.2 mm and 0.4 mm. Particularly for smaller distances 24, a very strong drop in the field strength can be found, for example, in the area above the center points of the conductor cross sections. There is even a change of sign. The curves for the different distances 24 intersect approximately at a point which is at a field strength of 2.5 10 ⁵ A / m. If there is now a scale made of plastic-bonded ferrite, which has a coercive field strength that corresponds to the value mentioned, with its surface parallel to the hairpin-shaped current conductor, its magnetization is set in a vertical direction upwards over a length that corresponds to the distance 14, to a depth of about 0.5 mm. In addition to the distance 14, the magnetic field strength in the region near the surface of the scale with a width of less than 1 mm is large enough to set the magnetization in the opposite direction here. To magnetize the next section of the scale, which should be periodically magnetized in an alternating direction after its completion, the position of the arrangement with the hairpin-shaped current conductor 11 is shifted exactly 1 mm to the right using a precise measuring arrangement. The direction of the current pulse that follows and therefore also that of the magnetic field is opposite to that of the first. The next section of the scale is magnetized vertically downwards. The areas of this section near the surface were magnetized in this direction already at the first pulse, so that a reversal of the direction of the magnetization already present does not have to take place. A field strength that exceeds the coercive field strength of the material also occurs again in the region of the first magnetized section near the surface. However, it corresponds to the direction of the magnetization inscribed there. No magnetic reversal is required. The lengths of the magnetized areas and also their magnetization value can thus be reproduced with high accuracy using a highly precise position measuring method for setting the position between the scale and the shaped current conductor 11.

The cross sections 17.2 and 17.3 shown in FIG. 4 for the hairpin-shaped current conductor 11 are advantageous if there are larger distances 14 between the outgoing and return lines. By it will decrease the field strengths to too low values in the middle between the and avoided return.

For writing scales whose magnetization is parallel to the surface of the scale 5, 6 and fig. 7 shaped shown Conductor as advantageous. Fig. 5 shows on a bracket 13 fixed supply line 12 and shaped current conductor 18. FIG. 6 illustrates that this shaped current conductor is band-shaped, the width 19 is substantially larger than the thickness. Different ways to The cross section of the band-shaped conductor 18 is shown in FIG. 7. The thickness distribution 20.1 and 20.3 ensures a uniform field strength of those pointing parallel to the band Field component under the belt over most of the width 19. An even Field strength of the named component under the conductor up to the edge and a strong gradient right next to the edge is with the cross section 20.2 and the cross section 20.4 in the event that the wire diameter is greater than the thickness of the between the two Wires located ribbon is reached. This is the magnetization of scale sections possible with high accuracy.

An arrangement for writing constructed in accordance with the features of the invention magnetic scales with the pulse method compared to the prior art only about 1/100 of the mass and volume, the electrical connection power is 1/100 reduced, the pulse repetition frequency and thus the effectiveness when writing scales has increased by a factor of 100 and the accuracy of the scales obtained has been increased by improved more than tenfold. In addition, health protection measures are no longer required in the new arrangement.

Arrangement for writing magnetic scales List of reference numbers

1

Shaped conductor

2

Pulse power source

3

capacitor bank

4

switch

5

control unit

6

capacitor

7

switch

8th

Connection of operating voltage

9

Control unit connection

10

shielding

11

Hairpin-shaped conductor

12

supply

13

bracket

14

distance

15

Dimension of the cross section

16

Dimension of the cross section

17

cross-section

17.1

Round cross section

17.2

Rectangular cross section with two round conductors

17.3

Rectangular cross section with four round conductors

18

stripline

19

Width of the strip conductor

20.1

Strip conductor thickness

20.2

Thickness distribution of the strip conductor

20.3

Composite strip conductor thickness

20.4

Composite strip conductor thickness

21

Field course at a distance of 0.05 mm

22

Field course at a distance of 0.2 mm

23

Field course at 0.4 mm distance

24

Distance from the molded conductor

Claims (28)

1. System for writing magnetic scales, which consists of components that include a shaped conductor (1) for producing a magnetic field at the location of the scale and a pulsed current source (2) for both current directions, which consists of a condenser battery (3), a commutator switch (4) and a control unit (5),
   characterised in that
   the shaped conductor consists of a conductor or conductor loop in each case with dimensions adapted to the size of the magnetisation to be induced uniformly in a magnetisation area to be written, the commutator switch comprising MOS transistors arranged as an H-bridge, and the components being integrated in a solid unit which is compact enough for the current switched by the commutator to increase to its maximum value through the shaped conductor in less than one microsecond.
2. System according to Claim 1,
   characterised in that
   thanks to the compact structure, the current path between the condenser battery (3) and the shaped conductor (1) has a resistance of less than 50 mΩ and the operating voltage of the system is in the low-voltage range.
3. System according to Claim 2,
   characterised in that
   the shaped conductor (1) for producing a magnetic field at the location of the scale has a conducting cross-section which is substantially smaller than the cross-section of the contact leads (12) from the condenser battery (3) directly to the shaped conductor (1).
4. System according to Claim 3,
   characterised in that
   the shaped conductor (1) is hairpin-shaped and has a cross-section (17) whose dimensions are substantially smaller than the distance (14) between the in-lead and the out-lead.
5. System according to Claim 4,
   characterised in that
   the cross-section ( 17) is a circle (17.1).
6. System according to Claim 5,
   characterised in that
   the diameter of the circle is 0.3 mm and the centre-to-centre distance (14) between the in-lead and the out-lead is 1 mm.
7. System according to Claim 4,
   characterised in that
   the cross-section (17) is rectangular and this rectangular cross-section (17) is occupied by two or more round wires (17.2, 17.3), the individual hairpin-shaped wires being electrically connected in series.
8. System according to Claim 3,
   characterised in that
   the shaped conductor (1) consists of a rectangle and has a cross-section whose dimensions are substantially smaller than the length and width of the rectangle.
9. System according to Claim 8,
   characterised in that
   the cross-section is a circle.
10. System according to Claim 8,
    characterised in that
    the cross-section is rectangular and this rectangular cross-section is occupied by two or more rectangular wires, the individual rectangular wires being electrically connected in series.
11. System according to Claim 3,
    characterised in that
    the shaped conductor (1) consists of a strip conductor (18) whose width (19) is substantially larger than its thickness (20.1).
12. System according to Claim 3,
    characterised in that
    the shaped conductor (1) consists of a strip conductor (18) whose width (19) is substantially larger than its thickness (20.2), the said thickness (20.2) being larger at the two edges than in the middle.
13. System according to Claim 3,
    characterised in that
    the shaped conductor (1) consists of a number of wires (20.3) immediately adjacent to one another.
14. System according to Claim 3,
    characterised in that
    the shaped conductor (1) consists of s strip conductor and two wires positioned symmetrically directly adjacent to the strip conductor, and the three said constituents (20.4) are electrically connected in series.
15. System according to any of Claims 3 to 14,
    characterised in that
    the shaped conductor (1) is fixed in a holder (13).
16. System according to Claim 15,
    characterised in that
    the shaped conductor (1) with its holder (13) can be exchanged.
17. System according to Claim 1,
    characterised in that
    each switch (7) consists of several MOS transistors connected in parallel.
18. System according to Claim 17,
    characterised in that
    the switches (7) can be closed by the control unit (5) after a short pulse time of a few microseconds.
19. System according to Claim 1,
    characterised in that
    the condenser battery (3) consists of electrolytic capacitors (6).
20. System according to Claim 19,
    characterised in that
    the charge of the condenser battery (3) is only reduced by a small proportion by each individual pulse.
21. System according to Claim 20,
    characterised in that
    the said small proportion amounts to 5%.
22. System according to Claim 21,
    characterised in that
    the current pulse sequence frequency is at most 50 s^-1.
23. System according to Claim 1,
    characterised in that
    the supply current of the system for current pulses of 2000 A is less than 500 mA.
24. System according to Claim 1,
    characterised in that
    the pulsed current source (2) is located within a screening box (10).
25. System according to Claim 1,
    characterised in that
    the rigidity of the mechanical structure is high enough for the forces produced by the pulsed current not to result in any miss-adjustment of the position of the shaped conductor (1) relative to the scale.
26. Use of a system according to any of Claims 1 to 25,
    characterised in that
    scales with periodic magnetisation in the measurement direction are produced.
27. Use of a system according to any of Claims 1 to 25,
    characterised in that
    scales with magnetisation areas of length determined by a code are produced.
28. Use of a system according to any of Claims 1 to 25,
    characterised in that
    the shaped conductor (1) is guided over the scale without contacting it.

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