CH711009B1 - Measuring standard with signal-compensating markings. - Google Patents

Abstract

The invention relates to a material measure (20) for an inductive position measuring system, which is formed by a material strip (23) made of a ferromagnetic material, the material strip (23) being elongated along a measuring direction (11). A large number of markings (21) are arranged in a row along the measuring direction (11), the markings (21) each being formed by openings or recesses of constant depth, the markings (21) each having a marking outline ( 50), and wherein the markings (21) encode a binary random number sequence. Each marking outline (50) is arranged completely within an associated, imaginary rectangle (60) with a first, a second, a third and a fourth rectangular side (61; 62; 63; 64), the distance between the third rectangular sides (63) being two Immediately adjacent imaginary rectangles (60) are each an integral multiple of a first pitch. According to the invention, the clear distance between two immediately adjacent imaginary rectangles (60) is different from an integral multiple of the first pitch.

Description

The invention relates to a material measure according to the preamble of claim 1.

[0002] EP 2 502 030 B1 discloses a material measure which is provided for use in a position measuring system. The position measuring system is an absolute position measuring system, whereby the markings on the measuring standard encode a binary random number sequence. The measuring standard is read inductively by a scanning device. Two types of measuring standards come into consideration for this, namely those made of a material with high electrical conductivity, for example copper (eddy current principle) and those made of a ferromagnetic material. The present invention is concerned with the latter type.

In inductive scanning, differentially interconnected pairs of coils are typically used in order to minimize the signal offset. In EP 2 502 030 B1, these are arranged next to one another transversely to the measuring direction, with two complementary rows of markings being used. The individual coils of a coil pair are hard-wired to one another. In the as yet unpublished German patent application with the file number 102014216036.7, the applicant has proposed a position measuring system which exclusively comprises individual coils which are arranged in a row in the measuring direction. These are dynamically interconnected in different ways during operation, so that the individual coils of a differential coil pair are arranged next to one another in the measuring direction. The present invention is concerned with a problem primarily encountered with the latter type. If the receiver coils are moved over a side boundary of a marking, the amplitude of the alternating voltage induced in the receiver coils does not change abruptly, rather there is a steady increase or decrease in the signal amplitude.

In the known position measuring systems, the markings are formed by openings or recesses in a strip of material. The corresponding marking outline is rectangular. The width and the clear spacing of the rectangles are each an integral multiple of a first pitch. Experiments by the applicant have shown that the induced alternating voltage of a single receiver coil, which is located exactly in the middle over an edge section of a marking outline oriented transversely to the measuring direction, has an amplitude that is greater than 50% of the maximum amplitude of the induced alternating voltage. This makes signal evaluation much more difficult.

One advantage of the invention is that the evaluation of the alternating voltages induced in the receiver coils for determining the position is particularly simple. In particular, the amplitude of the alternating voltages induced in the receiver coils is essentially 50% of the maximum signal amplitude at a defined point in relation to the graduation grid corresponding to the first graduation distance.

According to the independent claim 1 it is proposed that the clear distance between two immediately adjacent imaginary rectangles is different from an integral multiple of the first pitch. This results in a shift in the signal transition in relation to the pitch grid mentioned. Said clear distance is preferably selected so that the amplitude of the alternating voltages induced in the receiver coils at a defined point in relation to the graduation grid corresponding to the first graduation distance is essentially 50% of the maximum signal amplitude. The clear distance mentioned is the distance between the third and fourth sides of the rectangle of the immediately adjacent imaginary rectangles.

The strip of material preferably has a constant thickness, which is preferably smaller than the first pitch. The thickness is, for example, 0.3 mm, the first pitch being, for example, 1 mm. The width of the strip of material is preferably greater than the first pitch, for example 5 mm. The material strip is preferably made of stainless steel. The markings can be filled with a non-ferromagnetic material, wherein they are preferably empty or filled with air. The transmitter winding arrangement and / or the receiver coils are preferably designed as planar winding arrangements. The material measure is preferably part of a guide rail of a linear roller bearing, which is designed, for example, according to EP 1 052 480 B1. If several straight sections of the marking outline are assigned to the first or the second side of the rectangle, which run parallel to the measuring direction and are offset transversely to it, the above-mentioned rectangle sides preferably coincide with those straight sections that have the greatest length in total.

[0008] In the dependent claims, advantageous developments and improvements of the invention are specified.

It can be provided that the marking outlines each completely coincide with the associated imaginary rectangle. This is the embodiment which has the smallest difference compared to the known measuring standard, although the above-mentioned advantage is given. This measuring standard is just as easy to manufacture as the known measuring standard. A photochemical etching process is preferably used.

It can be provided that the third side of the rectangle is assigned a single straight third edge portion of the relevant marking outline, the fourth side of the rectangle being assigned a single straight fourth edge portion of the relevant marking outline, the third and fourth edge portions being arranged parallel to one another, where they enclose an angle different from 90 ° with the measuring direction. In the simplest case, the marking outline is designed in the form of a parallelogram. However, the marking outline can have a shape deviating from a parallelogram in the area of the first and second sides of the rectangle. This marking outline extends the movement path of the scanning device with respect to the material measure, in that the continuous signal transition takes place at a marking boundary. This ensures that in every position of the scanning device each marking boundary is detected by at least one receiver coil in such a way that an alternating voltage is induced, the amplitude of which lies between the minimum and the maximum amplitude of the induced alternating voltages. This simplifies the determination of the random number sequence read from the material measure. In addition, a positional error of the scanning device relative to the material measure transversely to the measuring direction has less of an effect than in the case of the rectangular shape of the marking outline suggested above.

It can be provided that the third side of the rectangle is assigned an outwardly or inwardly curved third edge portion of the marking outline, wherein the fourth side of the rectangle is assigned an outwardly or inwardly curved fourth edge portion of the marking outline. The third and fourth edge sections are preferably designed mirror-symmetrically to one another. It is conceivable that the third and fourth edge sections run in the form of a kink-free curve. However, the term “curved” is also intended to include courses of the third or fourth edge section which have a kink.

It can be provided that the third and the fourth edge section each have two straight subsections which enclose an angle that is greater than 90 °. This ensures that the signal profile is essentially linear in the area of a marking boundary. The third and / or the fourth edge section are preferably designed mirror-symmetrically with respect to a center line of the material measure. The third and / or the fourth edge section preferably have exactly two straight subsections.

[0013] It can be provided that the two straight subsections assigned to one another adjoin one another in a corner or in a circular radius. The circle radius is preferably made small.

It can be provided that the edge sections of the marking outline assigned to the first and second sides of the rectangle are designed mirror-symmetrically to one another. In this way, signal errors can be avoided, especially those that cannot be compensated.

It can be provided that the first side of the rectangle is assigned at least a fifth edge portion of the marking outline, which is curved with respect to the measuring direction, wherein the second side of the rectangle is assigned at least a sixth edge portion of the marking outline, which is curved with respect to the measuring direction. It has been shown that the amplitude of the alternating voltages induced in the receiver coils in some positions of the above-mentioned receiver coils in the area of a marking boundary can assume a value that is above the maximum value that theoretically should only occur when the receiver coil is completely above ferromagnetic material . It can also happen that the amplitude mentioned falls below a minimum value, which theoretically should only occur when the receiver coil is completely above air or a non-ferromagnetic material. This effect can be compensated for by the proposed design of the marking outline. However, the term “curved” should also include courses of the fifth or sixth edge section which have a kink. The fifth or the sixth edge section can optionally be bent inwards or outwards.

It can be provided that the fifth and / or the sixth edge section has at least one straight subsection.

It can be provided that the fifth and / or the sixth edge section has at least one kink-free curved sub-section.

It can be provided that the first edge sections of all marking outlines are arranged in alignment in the measuring direction, the second edge sections of all marking outlines being arranged in alignment in the measuring direction. When the position measuring system is in operation, the material measure is preferably placed under tensile stress in such a way that the specified first pitch is maintained very precisely. The proposed configuration of the outline of the marking prevents the material measure from assuming a course that deviates from the precisely straight shape. This would result in errors when reading the markings.

It can be provided that the distance between the third and fourth sides of the rectangle is between 20% and 50% of the first pitch greater than the closest integer multiple of the first pitch. With this design of a marking outline, the signal profile explained above as being preferred results in the area of a marking boundary.

The material measure according to the invention is preferably used in a position measuring system, wherein a scanning device is provided which has at least five receiver coils which are arranged in a row in the measuring direction, the scanning device having a transmitter winding arrangement which is immobile relative to the receiver coils, wherein the scanning device can be moved in the measuring direction along the measuring standard, the receiver coils, the transmitter winding arrangement and the measuring standard being arranged such that the position of the measuring standard relative to the scanning device influences the inductive coupling between the transmitter winding arrangement and the receiver coils. The spacing of all pairs of adjacent receiver coils in the measuring direction is preferably equal to a constant second pitch. The second pitch is preferably equal to or smaller than the first pitch, for example 0.8 mm.

It can be provided that the transmitter winding arrangement delimits a plurality of separate transmitter surfaces which are arranged in a row in the measuring direction, with at most one associated receiver coil being arranged in a transmitter surface. In such a position measuring system, the problem on which the invention is based occurs particularly strongly, so that the compensation according to the invention is particularly advantageous. The receiver coils are preferably arranged completely within the respectively assigned transmitter area.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination, but also in other combinations or on their own without departing from the scope of the present invention.

[0023] The invention is explained in more detail below with reference to the accompanying drawings. It shows: <tb> Fig. 1 <SEP> shows a roughly schematic representation of a position measuring system according to a first embodiment of the invention; <tb> Fig. 2 <SEP> a rough schematic representation of part of a material measure according to the first embodiment of the invention according to FIG. 1; <tb> Fig. 3 <SEP> shows a roughly schematic representation of part of a material measure according to a second embodiment of the invention; <tb> Fig. 4 <SEP> shows a roughly schematic representation of part of a material measure according to a third embodiment of the invention; <tb> Fig. 5 <SEP> shows a roughly schematic representation of part of a material measure according to a fourth embodiment of the invention; <tb> Fig. 6 <SEP> shows a roughly schematic cross section of the position measuring system according to FIG. 1, the markings being designed as openings; and <tb> Fig. 7 <SEP> shows a representation corresponding to FIG. 6, the markings being designed as recesses.

Fig. 1 shows a roughly schematic representation of a position measuring system 10 according to a first embodiment of the invention. The position measuring system 10 comprises a measuring standard 20 and a scanning device 30. The measuring standard 20 is designed as a material strip 23 made of a ferromagnetic material, for example stainless steel, wherein it has a constant thickness of 0.3 mm, for example. The material measure 20 extends with a constant width 27 in a measuring direction 11. A plurality of markings 21 are arranged in a row along the measurement direction 11 on the material measure 20, which are based on a constant first pitch λ. The markings 21 can optionally be designed as openings (no. 22 in FIG. 6) or as recesses (no. 22a in FIG. 7) with a constant depth. The markings 21 can have two states, they can be present or not. The markings 21 encode a binary random number sequence, a first pitch λ corresponding to a binary digit of this code. The shape of the markings is explained below with reference to FIGS. 2 to 5. The markings 21 are designed in such a way that no transverse webs are required in the material strip, which are arranged regularly spaced apart on the material strip 23 with the first pitch λ. At right angles to the measuring direction 11 on both sides of the markings 21, the metal strip 23 has a side web 24 each, so that a coherent measuring standard 20 results. The markings 21 are preferably designed as a free space filled with air. But they can also be filled with a material which is not ferromagnetic, for example brass.

The scanning device 30 is movable in the measuring direction 11 with respect to the measuring standard 20. Preferably, the measuring standard 20 is attached to the guide rail of a linear roller bearing, the scanning device 30 being attached to the associated guide carriage. A corresponding linear roller bearing is known from DE 10 2007 042 796 A1. The scanning device 30 comprises an evaluation assembly 34, which is preferably designed in the form of a separate electronic circuit board. The remainder of the scanning device 30, namely the transmitter winding arrangement 41, the receiver coils 40, the switching device 70 and the operational amplifier 80 are arranged in the immediate vicinity of the measuring standard 20, while the evaluation module 34, on the other hand, can have a greater spatial distance from the measuring standard 20.

The transmitter winding arrangement 41 and the receiver coils 40 are each designed as planar winding arrangements. In FIG. 1, only one turn is shown in each case, with both the transmitter turn arrangement 41 and the receiver coils 40 actually each having a plurality of essentially parallel turns. In FIG. 1, a center line 25 is shown both in the transmitter winding arrangement 41 and in the measuring standard 20. Contrary to the illustration in FIG. 1, these two center lines 25 are congruent one above the other, the transmitter winding arrangement 41 and the receiver coils 40 being arranged at a small distance from the measuring standard 20 (cf. FIGS. 6 and 7). The material measure 20 thus influences the inductive coupling between the transmitter winding arrangement 41 and the receiver coils 40. An alternating current fed into the transmitter winding arrangement 41 induces an alternating voltage in the receiver coils 40, the amplitude of which depends on the position of the scanning device 30 relative to the material measure 20.

In the present case, the transmitter winding arrangement 41 is designed as a meandering structure, delimiting several separate transmitter surfaces 42 which are arranged in a row in the measuring direction 11. The transmitter turn arrangement 41 comprises a first and second group 44; 45 of serpentine conductor tracks 43 which intersect several times along the measuring direction 11. At the point marked with the number 46, the said conductor tracks 43 are connected to one another in such a way that the transmitter winding arrangement 41 is formed by a single continuous conductor track. The transmitter winding arrangement 41 can alternatively also be composed of a plurality of individual coils which each delimit a single assigned transmitter surface 42, whereby they are optionally connected in series or in parallel. If the transmitter winding arrangement 41 is fed with an alternating current from the alternating current source 31, an electromagnetic alternating field of essentially the same magnitude results in all transmitter surfaces 42, the field direction being opposite in immediately adjacent transmitter surfaces 42. The alternating current source 31 is preferably part of the evaluation assembly 34.

A single receiver coil 40 is completely arranged in each of the transmitter surfaces 42. The operational amplifier 80, which is preferably designed to be fully differential, is arranged in spatial proximity to the receiver coils 40. Two adjacent receiver coils 40 each have a constant second pitch δ in the measuring direction 11, which is, for example, 0.8 mm. The wiring of the operational amplifier 80 is shown in a greatly simplified manner in FIG. 1, with only the two feedback resistors 85, which are characteristic of the fully differential operational amplifier 80; 86 are shown. The first feedback resistor 85 connects the first input terminal 81 of the operational amplifier 80 to the first output terminal 83 of the operational amplifier 80. The second feedback resistor 86 connects the second input terminal 82 of the operational amplifier 80 to the second output terminal 84 of the operational amplifier 80.

The first and the second output port 83; 84 are connected on the input side to an analog-digital converter 32 so that the analog-digital converter 32 can measure the corresponding electrical measurement voltage M. The corresponding digital value is passed on to a programmable digital computer 33. The programmable digital computer 33 and the analog / digital converter 32 are preferably part of the evaluation assembly 34, and they are most preferably designed in the form of a microcontroller.

The first and the second input port 81; 82 are connected to the various receiver coils 40 via a switching device 70. The switching device 70 comprises a first signal line 75 which is connected to the first input connection point 81 of the operational amplifier 80. A second signal line 76 is also connected to the second input connection point 82 of the operational amplifier 80. One connection of each receiver coil 40 is connected to a third signal line 77. The respective other connection of a receiver coil 40 is via an associated switching means 71; 72 either with the first or with the second signal line 75; 76 connected. Preferably, each switching means 71; 72; 73; 74 has a first state in which it has a first electrical resistance, wherein it has a second state in which it has a second electrical resistance, the second electrical resistance being at least 1000 times greater than the first electrical resistance, the at least one switching means can be switched between the first and the second state. In the context of the present application, it is assumed that a receiver coil 40 in the second state of the associated switching means 71; 72 is not connected to the operational amplifier 80. The switching means 71; 72; 73; 74 used on the basis of semiconductors. A first electrical resistance of 0.9 Ω can thus be achieved, for example, and a second electrical resistance can be achieved which results in a signal attenuation of at least 60 dB. A corresponding switching device is the subject of the data sheet, which was available on March 19, 2015 at the Internet address http://www.ti.com/lit/ds/symlink/ts5a623157.pdf.

In Fig. 1, seven receiver coils 40 are shown as an example, which are each identified with an index n that counts up along the measuring direction 11. It goes without saying that the position measuring system 10 can have significantly more, for example thirty, receiver coils 40. The receiver coils 40 with the indices n = 1, 3, 5, 7 are each connected to the first signal line 75 via a first switching means 71. The receiver coils 40 with the indices n = 2, 4, 6 arranged in between are each connected to the second signal line 76 via a second switching means 72. The interconnection described above leads to the two selected receiver coils being differentially interconnected, with their input being connected to the operational amplifier 80. Correspondingly, external interference fields which act in the same way on both of the aforementioned receiver coils 40 do not affect the measurement voltage M. For the correct differential interconnection of two receiver coils, the winding direction of the relevant receiver coils and which connection is connected to the third signal line 77 are important.

With the fourth switching means 74, the third signal line 77 is connected to the first input connection point 81 of the operational amplifier 80. Thus, only a single receiver coil 40 is connected on the input side to the operational amplifier 80, which is connected to the second signal line 76 via a second switching device 72. If a single receiver coil 40 is to be used, which is connected to the first signal line 75 via a first switching means 71, then only the third switching means 73 is closed. The third signal line 77 is connected to the second input connection point 82 of the operational amplifier 80 by the third switching means 73.

The first to fourth switching means 71; 72; 73; 74 are preferably controlled by the programmable digital computer 33, the corresponding control lines not being shown in FIG. 1.

Fig. 2 shows a rough schematic representation of part of a measuring standard 20 according to the first embodiment of the invention according to FIG. 1. Below the measuring standard 20 is a diagram in which a voltage ratio k is plotted over a position x. The position x is the position of an individual receiver coil (No. 40 in FIG. 1) relative to the material measure 20. The voltage ratio k indicates the amplitude of the alternating voltage induced in the receiver coil under consideration. The value 100% occurs when the receiver coil is completely over ferromagnetic material. When the receiver coil is completely above a marking 21, the voltage ratio is approximately 0%, since the inductive coupling between the transmitter winding arrangement and the receiver coil is very weak due to the lack of ferromagnetic material.

In the first embodiment, the marking outline 50 is rectangular, so that the imaginary rectangle 60 completely coincides with the marking outline 50 according to the independent claim. The imaginary rectangle 60 has a first, a second, a third and a fourth rectangle side 61; 62; 63; 64. The first and second sides of the rectangle 61; 62 run parallel to the measuring direction 11, the third and fourth sides of the rectangle 63; 64 run perpendicular to the measuring direction 11. The distance 65 between the first and second sides of the rectangle 61; 62 corresponds to the width of the marking 21. This is made somewhat smaller than the width 27 of the material strip 23, so that the two opposite side webs 24 remain, which hold the material strip 23 together in one piece. The distance 66 between the third and fourth sides of the rectangle 63; 64 is the length of the marking 21. In the present case, this is somewhat larger than an integer multiple of the first pitch λ. As can be seen from FIG. 1, the first pitch λ can be determined by measuring, for example, the distances between the third rectangle sides 63 of all markings 21, the shortest of these distances being twice the first pitch λ.

The distance 66 or the clear distance (no. 67 in Fig. 1) of two immediately adjacent imaginary rectangles 60 is chosen so that the distance 13 of the 50% values 12 of the voltage ratio k as precisely as possible an integral multiple of the first Pitch λ is. If the first pitch λ is, for example, 1.0 mm, the distance 66 can be, for example, 1.4 mm, the clear distance (No. 67 in FIG. 1) being, for example, 0.6 mm.

FIG. 3 shows a roughly schematic representation of part of a measuring standard 20 according to a second embodiment of the invention. The marking outline 50 is designed in the form of a parallelogram, so that it no longer completely coincides with the imaginary rectangle 60. The imaginary rectangle 60 is shown in Fig. 3 with broken lines. The only straight first edge section 51 of the marking outline 50 is located completely on the first side of the rectangle 61, the first side of the rectangle 61 being longer than the first edge section 51. The only straight second edge section 52 of the marking outline 50 is located completely on the second side of the rectangle 62, the second side of the rectangle 62 being longer than the second edge section 52.

A single straight third edge section 53 of the relevant marking outline 50 is assigned to the third side 63 of the rectangle and is arranged completely within the imaginary rectangle 60. A single straight fourth edge section 54 of the relevant marking outline 50 is assigned to the fourth side 64 of the rectangle and is arranged completely within the imaginary rectangle 60. The third and fourth edge portions 53; 54 are arranged parallel to one another, enclosing an angle different from 90 ° with the measuring direction 11.

The point 68 at which the third side of the rectangle 63 coincides with the marking outline 50 is the corner between the third and the second edge section 53; 52. The point 69 at which the fourth side of the rectangle 64 coincides with the marking outline 50 is the corner between the fourth and the first edge portion 54; 51.

As a comparison of FIGS. 2 and 3 shows, the curve of the voltage ratio k over the position x in the region of the 50% values 12 in the second embodiment is significantly less steep than in the first embodiment. The distance 66 or the clear width (No. 67 in FIG. 1) is again selected so that the path distance 13 of the 50% values 12 of the voltage ratio k is as precisely as possible an integral multiple of the first pitch λ.

FIG. 4 shows a rough schematic representation of part of a measuring standard 20 according to a third embodiment of the invention. The imaginary rectangle 60 is shown in Fig. 4 with broken lines. The only straight first edge section 51 of the marking outline 50 is located completely on the first side of the rectangle 61, the first side of the rectangle 61 being longer than the first edge section 51. The only straight second edge section 52 of the marking outline 50 is located completely on the second side of the rectangle 62, the second side of the rectangle 62 being longer than the second edge section 52.

The third side of the rectangle 63 is assigned an outwardly curved third edge section 53a of the marking outline 50. The fourth side of the rectangle 64 is assigned an outwardly curved fourth edge section 54a of the marking outline 50. The third and fourth edge portions 53a; 54a are mirror-symmetrical to one another. The third and fourth edge portions 53a; 54a each have exactly two straight subsections 57 which enclose an angle which is greater than 90 °. The two straight subsections 57 assigned to one another adjoin one another in a corner 58. The corners 58 form the points 68; 69, on which the third and fourth sides of the rectangle 63; 64 coincides with the marking outline 50.

The course of the stress ratio k over the position x in the area of the 50% values 12 is essentially the same in the third embodiment as in the second embodiment according to FIG. 3. The distance 66 or the clear width (No. 67 in Fig. 1) is again selected so that the distance 13 of the 50% values 12 of the voltage ratio k is as precisely as possible an integral multiple of the first pitch λ.

The marking outline 50 according to the third embodiment is formed overall mirror-symmetrically with respect to the center line 25 of the material measure 20. This avoids errors when scanning the material measure 20.

FIG. 5 shows a rough schematic representation of part of a measuring standard 20 according to a fourth embodiment of the invention. This embodiment relates to several further deviations of the actual signal shape from the ideal signal shape for signal evaluation. The fourth embodiment according to FIG. 5 is a modification of the first embodiment according to FIG. 2, but it can also be combined with the second or third embodiment according to FIGS. 3 and 4, respectively.

In Fig. 5, the signal shape is shown with a dashed line, which can result when only the first embodiment of FIG. 2 is used. A solid line shows the signal shape which results from the compensation measures explained below and which is particularly suitable for simple signal evaluation. A total of three types of deviations 14a result between these signal forms; 14b; 15a; 15b; 16, which will be discussed in detail below.

The plateau effect 16 can be observed when the individual coil under consideration is completely above the ferromagnetic material of the material strip 23 at a large distance from a marking 21. The signal amplitude can then be somewhat higher than when the individual coil is located a short distance from a marking 21 completely above the ferromagnetic material of the material strip 23. This plateau effect 16 can be counteracted by auxiliary markings 21a, which are very narrow compared to the information-carrying markings 21. The auxiliary markings 21a are arranged precisely where a plateau effect 16 is shown without auxiliary markings 21a. The width of the auxiliary markings 21a is selected to be just large enough that the plateau effect 16 disappears.

The overshoots 14a; 14b can be observed when the individual coil under consideration is shortly before or shortly after a marking boundary 53; 54 is above the ferromagnetic material of the material strip 23. The overshoots 14a; 14b can be countered by removing ferromagnetic material in the corresponding area of the material strip 23. For this purpose, a fifth edge section 55 of the marking outline 50 is provided on the first rectangular side 61 of the auxiliary marking 21a, which extends outwardly with respect to the measuring direction 11, with at least one sixth edge section 56 of the marking outline 50 of the auxiliary marking 21a being assigned to the second rectangular side 62, which is associated with the auxiliary marking 21a the measuring direction 11 is curved outwards.

The undershoots 15a; 15b can be observed when the individual coil being viewed is just behind or just before a marking boundary 53; 54 is above the free space of a marking 21. The undershoots 15a; 15b can be counteracted by adding ferromagnetic material in the corresponding area of the material strip 23. For this purpose, a fifth edge section 55 of the marking outline 50 is provided on the first rectangular side 61 of the marking 21, which is curved inward with respect to the measuring direction 11, with the second rectangular side 62 of the marking 21 being assigned at least one sixth edge section 56 of the marking outline 50, which is associated with the measuring direction 11 is curved inward.

The fifth and / or the sixth edge section 55; 56 can have at least one straight sub-section 57a, as is shown in FIG. 5 for overshoot 14b and undershoot 15b. The fifth and / or the sixth edge section 55; 56 can have a kink-free bent lower section 57b, as is shown in FIG. 5 for the overshoot 14a and the undershoot 15a.

FIG. 6 shows a roughly schematic cross section of the position measuring system 10 according to FIG. 1, the markings 21 being designed as openings 22. Correspondingly, the markings 21 penetrate the entire thickness 26 of the material measure 20. The marking outline 50 is essentially constant over the entire thickness 26 of the material strip 23. Deviations can arise due to tolerances due to the preferred production with a photochemical etching process. The openings 22 are preferably etched simultaneously from the strip of material 23 from two opposite sides, so that the etching time is short.

The arrangement of the receiver coils 40 and the transmitter winding arrangement 41 relative to the material measure 20 can also be seen in FIG. 6. The receiver coils 40 and the transmitter winding arrangement 41 are each designed as planar winding arrangements, which are preferably produced by means of a photochemical etching process. In FIG. 6, only a single layer is provided for the receiver coils 40 and the transmitter winding arrangement 41, it also being possible for more layers to be provided in order to make the number of turns of the winding as large as possible. The individual layers are each separated from one another by an insulating layer 47, which can consist of polyimide, for example. This plastic is electrically non-conductive and can withstand high temperatures. If the receiver coils 40 and / or the transmitter winding arrangement 41 each have a plurality of layers, they are preferably electrically connected to one another via vias, the vias penetrating one or more associated insulating layers.

The sensor distance 17 between the material measure 20 and the assembly containing the receiver coils 40 and the transmitter winding arrangement 41 is preferably made small, most preferably smaller than the first pitch λ.

FIG. 7 shows a representation corresponding to FIG. 6, the markings 21 being designed as recesses 22a. The recesses 22a have a constant depth 22b, which is, for example, equal to half the thickness 26 of the material strip 23. The recesses 22a are preferably produced by a photochemical etching process, the etching taking place only from one side of the material strip 23. Since the etching depth and thus the depth 22b of the recesses 22a can only be controlled with difficulty, the openings according to FIG. 6 are preferred.

For the rest, reference is made to the explanations relating to FIG. 6, with the same or corresponding parts in FIGS. 6 and 7 being provided with the same reference numbers.

Reference number

Λ first division distance δ second division distance M measurement voltage k voltage ratio x position of an individual receiver coil relative to the material measure 10 position measuring system 11 measurement direction 12 50% value of the voltage ratio 13 distance of the 50% values of the voltage ratio 14a overshoot 14b overshoot 15a undershoot 15b undershoot 16 Plateau effect 17 Sensor spacing 20 Measuring standard 21 Marking 21a Auxiliary marking 22 Opening 22a Recess 22b Depth of recess 23 Material tape 24 Side bar 25 Center line 26 Thickness of tape measure 27 Width of tape measure 30 Scanning device 31 AC power source 32 Analog-digital converter 33 Programmable digital computer 34 Evaluation module 40 Receiver coil 41 Transmitter winding arrangement 42 transmitter surface 43 serpentine conductor track 44 first group 45 second group 46 boundary between the two groups of serpentine conductor tracks 47 insulating layer 50 marking outline 51 first edge section 52 second edge section 53 third edge section 53a third edge section 54 fourth edge section 54a fourth edge section 55 fifth edge section 56 sixth edge section 57 straight subsection 57a straight subsection 57b kink-free curved subsection 58 corner 60 imaginary rectangle 61 first rectangle side 62 second rectangle side 63 third rectangle side 64 fourth rectangle side 65 spacing between first and second rectangle side 66 distance between third and fourth rectangle side 67 clear distance between two adjacent rectangles 68 point at which the third rectangle side coincides with the marking outline 69 point at which the fourth rectangle side coincides with the marking outline 70 switching device 71 first switching means 72 second switching means 73 third switching means 74 fourth switching means 75 first signal line 76 second signal line 77 third signal line 80 operational amplifier 81 first input connection point of operational amplifier 82 second Input connection point of operational amplifier 83 first output connection point of operational amplifier 84 second output connection point of operational amplifier 85 first feedback resistor 86 second feedback resistor

Claims (14)

1. Measuring standard (20) for use in a position measuring system (10), wherein the measuring standard (20) is formed by a material strip (23) made of a ferromagnetic material, the material strip (23) being elongated along a measuring direction (11) is formed, wherein a plurality of markings (21; 21a) are arranged on the strip of material in a row along the measuring direction (11), the markings (21) each being formed by openings (22) or recesses (22a) of constant depth the markings (21) each having a marking outline (50), at least some of the markings (21) encoding a binary random number sequence, wherein each marking outline (50) is arranged completely within an associated, imaginary rectangle (60) with a first, a second, a third and a fourth side of the rectangle (61; 62; 63; 64), said marking outline (50) at least in sections can coincide with said imaginary rectangle (60), the first and second sides of the rectangle (61; 62) running parallel to the measuring direction (11), the marking outlines (50) each having at least one straight first edge section (51) which coincides with an associated first rectangular side (61), the marking outlines (50) each having at least one straight second edge section (52) which coincides with an associated second rectangular side (62), the third and fourth rectangular sides (63; 64) each coincide at least at one point (68; 69) with the assigned marking outline (50), the distance between the third rectangle sides (63) z wherever immediately adjacent imaginary rectangles (60) are in each case an integral multiple of a first pitch (λ), characterized in that the clear distance (67) between two immediately adjacent, imaginary rectangles (60) is different from an integral multiple of the first pitch (λ). 2. Material measure according to claim 1, wherein the marking outlines (50) each completely coincide with the associated imaginary rectangle (60). 3. Material measure according to claim 1, wherein the third rectangular side (63) is assigned a single straight third edge section (53) of the relevant marking outline (50), the fourth rectangular side (64) being assigned a single straight fourth edge section (64) of the relevant marking outline (50), the third and fourth edge sections (53; 54) are arranged parallel to one another, enclosing an angle different from 90 ° with the measuring direction (11). 4. Material measure according to claim 1, The third side of the rectangle (63) is assigned an outwardly or inwardly curved third edge section (53a) of the marking outline (50), the fourth side of the rectangle (64) having an outwardly or inwardly curved fourth edge section (54a) of the marking outline (50) is assigned. 5. Material measure according to claim 4, wherein the third and the fourth edge section (53a; 54a) each have two straight sub-sections (57) which enclose an angle which is greater than 90 °. 6. Material measure according to claim 5, wherein the two straight subsections (57) assigned to one another adjoin one another in a corner (58) or in a circular radius. 7. Material measure according to one of the preceding claims, wherein the first and the second edge section (51; 52) of the marking outline (50) are mirror-symmetrical to one another. 8. Material measure according to one of the preceding claims, the first side of the rectangle (61) being assigned at least one fifth edge section (55) of the marking outline (50), which is curved with respect to the measuring direction (11), the second side of the rectangle (62) having at least a sixth edge section (56) of the marking outline (50) ) is assigned, which is curved with respect to the measuring direction (11). 9. Material measure according to claim 8, wherein the fifth and / or the sixth edge section (55; 56) has at least one straight sub-section (57a). 10. Material measure according to claim 8 or 9, wherein the fifth and / or the sixth edge section (55; 56) has at least one kink-free curved sub-section (57b). 11. Material measure according to one of the preceding claims, wherein the first edge sections (51) of all marking outlines (50) are arranged in alignment in the measuring direction (11), the second edge portions (52) of all marking outlines (50) being arranged in alignment in the measuring direction (11). 12. Material measure according to one of the preceding claims, wherein a distance (66) of the third and fourth sides of the rectangle (63; 64) of the same imaginary rectangle (60) between 20% and 50% of the first division distance (λ) greater than the integer multiple of the first division distance closest to said distance (66) (λ) is. 13. Position measuring system (10) with a material measure (20) according to one of the preceding claims, wherein a scanning device (30) is provided which has at least five receiver coils (40) which are arranged in a row in the measuring direction (11), the scanning device (30) having a transmitter winding arrangement (41) which is immovable relative to the receiver coils ( 40), the scanning device (30) being movable in the measuring direction (11) along the measuring standard (20), the receiver coils (40), the transmitter winding arrangement (41) and the measuring standard (20) being arranged so that the position of the Measuring standard (20) with respect to the scanning device (30) influences the inductive coupling between the transmitter winding arrangement (41) and the receiver coils (40). 14. Material measure according to one of the preceding claims, wherein the transmitter winding arrangement (41) delimits several separate transmitter surfaces (42) which are arranged in a row in the measuring direction (11), with at most one associated receiver coil (40) being arranged in a transmitter surface (42).