POSITION-MEASURING DEVICE FOR MEASURING AN ABSOLUTE POSITION

Abstract

A position-measuring device and a corresponding method for measuring an absolute position includes a material measure having a first binary code and a second binary code and a sensor device that scans the first and second binary codes. The sensor device scans the first binary code, which has a first number of code words, each having the same code word length. The second binary code of the material measure forms a portion of the first binary code and has a second number of the code words that can be mapped onto the first binary code.

Claims

1. A position-measuring device for measuring an absolute position, the position-measuring device comprising: a measuring standard that has a binary code and a sensor device that scans the binary code, wherein the binary code includes a first binary code having a first number of code words that have the same code word length and the sensor device scans the first binary code; and wherein the binary code includes a second binary code that forms a portion of the first binary code, the second binary code having a second number of code words that can be mapped onto the first binary code.

2. The position-measuring device as claimed in claim 1, wherein the second binary code can be mapped onto the first binary code by a predefined mapping rule.

3. The position-measuring device as claimed in claim 1, wherein the first and the second binary codes comprise unique code words, each of which is assigned to a unique code position with the code word length over which the first and the second binary codes extend.

4. The position-measuring device as claimed in claim 3, wherein the code positions of the second binary code can be mapped onto the code positions of the first binary code by a mapping rule.

5. The position-measuring device as claimed in claim 4, wherein the mapping takes place taking a scaling factor and/or a position displacement into account.

6. The position-measuring device as claimed in claim 5, wherein the scaling factor establishes the relationship between the first number of code words and the second number of code words.

7. The position-measuring device as claimed in claim 3, wherein the code words of the second binary code have the same sequence as the code words of the first binary code, in particular in the portion of the first binary code.

8. The position-measuring device as claimed in claim 1, further comprising a further processing unit for processing the scanned sensor signals and/or for converting the code words into code positions.

9. The position-measuring device as claimed in claim 3, wherein the conversion of the code words into the code positions takes place by means of a look-up table and/or by means of a feedback shift register.

10. The position-measuring device as claimed in claim 1, wherein the first binary code with the first number of code words having the same code word length is a complete code in which all possible M=2.sup.L bit combinations occur.

11. The position-measuring device as claimed in claim 1, wherein the first binary code and/or the second binary code is a closed code in which, on exceeding a last code position of a last one of the code words in a first code position, again follows.

12. The position-measuring device as claimed in claim 1, wherein the measuring standard is a rotary measuring standard, in particular as a circular disk or roller.

13. The position-measuring device as claimed in claim 8, wherein for mapping the second binary code onto the first binary code, unique code positions are predefined through a start value and an end value of the second binary code within the first binary code, or through the second number of code words and the start value, or the end value of the second binary code within the first binary code in the further processing unit.

14. The position-measuring device as claimed in claim 3, wherein the second binary code has a start position that can be subtracted from a respective one of the code positions of the measuring standard to map the second binary code onto the first binary code.

15. The position-measuring device as claimed in claim 1, wherein the sensor device comprises at least a variety of sensor elements, so that the total code word length of a code word can be captured simultaneously or in sequence.

16. The position-measuring device as claimed in claim 1, wherein the position-measuring device is designed as a measuring or counting position-measuring device.

17. A method for measuring an absolute position, the method comprising: providing a position-measuring device for measuring an absolute position with a measuring standard that has a binary code; and scanning the binary code with a sensor device, wherein the sensor device scans a first binary code that has a first number of code words that have the same code word length, wherein the binary code of the measuring standard is a binary code that forms a portion of the first binary code with a second number of code words that are mapped onto the first binary code.

18. The method as claimed in claim 17, further comprising selecting the binary codes to have unique code words; assigning each of the code words to a unique code position with a code word length over which the binary codes extend; and mapping the code positions of the second binary code onto the code positions of the first binary code by means of a mapping rule.

19. The method as claimed in claim 18, wherein the mapping takes a scaling factor and/or a position displacement into account.

20. The method as claimed in claim 19, wherein the scaling factor establishes a relationship between the first number of code words and the second number of code words.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Further details and advantages of the invention are to be explained in more detail below with reference to the exemplary embodiments shown in the drawings, in which:

[0054] FIG. 1a shows a position-measuring device with a measuring standard comprising a first binary code;

[0055] FIG. 1b shows a tabular illustration of an exemplary embodiment of a first binary code according to FIG. 1a;

[0056] FIG. 2 shows a measuring standard according to FIG. 1 that has been shortened by a predefined cut-out area, so that only a portion of the first binary code of FIG. 1a remains;

[0057] FIG. 3a shows a position-measuring device with a shortened measuring standard comprising a second binary code that forms a portion of the first binary code;

[0058] FIG. 3b shows a tabular illustration of an exemplary embodiment of a first binary code according to FIG. 3a;

[0059] FIG. 4 shows the arrangement according to FIG. 1a;

[0060] FIG. 5 shows the arrangement according to FIG. 2;

[0061] FIG. 6 shows the arrangement according to FIG. 3a; and

[0062] FIG. 7 shows a block diagram of a position-measuring device with a further processing unit.

DETAILED DESCRIPTION

[0063] Parts of a position-measuring device 3 which can be used in very different technical fields to ascertain the absolute position of a component, not shown in more detail, are illustrated in FIGS. 1 to 3. The block diagram of a position-measuring device 3 with a division into function blocks is shown in FIG. 7.

[0064] The position-measuring device 3 can be embodied, as required, as an optical or as a magnetic position-measuring device 3. Such a position-measuring device 3 can comprise a measuring standard 4 as well as a sensor device 6. In the case of an optical position-measuring device 3, the measuring standard 4 can comprise differently reflective or light-transmitting regions 9, wherein the scale of the measuring standard 4 is illuminated by a light source, not illustrated. In the case of a magnetic position-measuring device 3, the scale of the measuring standard 4 comprises, on the other hand, magnetic position markings 9, that differ in their magnetization. Depending on the application, the measuring standard 4 can moreover comprise a linear or circular scale.

[0065] According to the present exemplary embodiment, the measuring standard 4 is designed as a rotary measuring standard 4. The measuring standard 4 comprises a position track 5 that comprises the encoded regions in the form of code position markings 9 that are designed in the manner of a binary code 1, 2, and which each correspond to one bit of the binary code 1, 2. The code position markings 9 can be scanned with the aid of the sensor device 6 and, in particular, by means of a variety of sensor elements 7. The capture of the movement of the code position marking 9 of the position track 5 supplies code positions that reproduce the change in the position. Depending on the application, multiple position tracks 5 can also be provided, such as for example a further, possibly inverted, absolute track, or also an index track or incremental track or the like, by means of which one or a plurality of index markings or increments can be scanned.

[0066] During the operation of the position-measuring device 3, the code position markings 9 of the position track 5 are moved in accordance with the present exemplary embodiment with a circular measuring standard 4, along a circular track with a radius around the axis of rotation in the direction of movement B, and are detected by the sensor elements 7 of the sensor device 6. The measuring standard 4 can preferably be designed for this purpose as a rotary measuring standard 4, in particular as a circular disk or roller. The measuring standard 4 can alternatively, for example, also be designed as a linear scale.

[0067] The code position markings 9 of the position track 5 of the measuring standard 4 are, in the present exemplary embodiment, designed as a binary code 1, 2. The binary code 1, 2 can, for example, be a pseudo-random code that can be generated by means of a pseudo-random number generator. With a predetermined start value S, an apparently random bit sequence, repeating itself cyclically, is generated in this way. The binary code 1, 2 is designed here in such a way that a new code word C is always generated in response to a displacement. There is no discontinuity even at the end of the closed binary code 1, 2, where the start value S begins again. The binary codes 1, 2 can in particular be designed as shift codes. This means that when displaced by one or a plurality of locations, a new, and again unique, code word C is generated.

[0068] In FIG. 1 the measuring standard 4 comprises a scale that is encoded with the first binary code 1. The first binary code 1 has a first number M of code words C, each of which has a predefined code word length L. The code word length L can be chosen according to need, and have an arbitrary number of bits, in particular N bits. According to the present exemplary embodiment, the code words C have a code word length L of five bits. The first number M of code words C is here selected to be 32, i.e. 2.sup.5 bits. Other configurations are, however, also conceivable, in which a different first number M of code words C and/or a different code word length L is chosen. With the aid of this binary code 1, all the code positions P.sub.M can be uniquely specified, so that in particular all of the code positions assigned to the code numbers CN.sub.M in code space, and thus the physical code positions P.sub.M, in particular angle values, can be uniquely specified on the measuring standard 4. In particular, the binary code 1 used is a complete and/or closed binary code 1. A complete code 1 here is one in which all of the M=2.sup.L bit combinations occur. A closed binary code 1, 2 does not have any discontinuities, not even from the end of the binary code 1, 2 to its freely definable beginning.

[0069] A discontinuity in the binary code 1, 2 would be defined here as a continuous change in the code positions P.sub.M, P.sub.m, not consisting of a single step, when the shift code is displaced by one bit. A binary code 1, 2 with a discontinuity allows the execution and evaluation according to the invention with restrictions and/or in portions of the bit sequence.

[0070] As can be seen in FIG. 1b, the first binary code 1 in the present case, in particular beginning with CN.sub.M=0 and the code position P.sub.M=0, comprises the following bit sequence: 01001 01100 11111 00011 01110 10100 00. With a code word length L=5, a total of M=32 code words C can be formed with this complete code 1, wherein the code words C can each be generated from the preceding code word C through shift operations of 1 bit in each case, and are unique. These code words C are correspondingly numbered in sequence in the table in FIG. 1b with the code numbers CN.sub.M, and form the code space. As can also be seen in this table, a unique physical code position P.sub.M (in degrees) on the measuring standard 4 with the code word length L spanned by the binary code 1, can also be assigned to each unique code word C. The respective code number CN.sub.M in the table here corresponds to the code position P.sub.M=CN.sub.M×360°/M, wherein physical code position P.sub.M is assigned to the last of the L bits in the clockwise sense of a code word C. In FIG. 1a and FIG. 1b the code word C 00000 with the code number CN.sub.M 0 in the code space, and the physical code position P.sub.M=0 have been chosen as the start position. The full angle of 360° corresponds, in linear systems, to the segment with the M code positions P.sub.M.

[0071] These unique code positions P.sub.M can now be read out by means of the sensor device 6 spatially assigned to the measuring standard 4. The position markings 9 can be scanned for this purpose by means of the sensor elements 2 of the sensor device 6. The sensor device 6 comprises, according to the present exemplary embodiment, five sensor elements 7 that are arranged next to one another in the radial direction. In the present case this corresponds to the code word length L. The invention is not, however, restricted to this. Rather, further configurations are conceivable in which more or fewer sensor elements 7 are provided. It is particularly preferable for the sensor device 6 to have at least a variety of sensor elements 7, so that the total code word length L of a code word C can be captured simultaneously or in sequence, in particularly partially or as a whole in sequence.

[0072] The sensor elements 7 each have essentially the same length and are arranged—apart from a technical minimum distance—on a sensor track 11. The length of the sensor elements 7 is preferably adjusted to the length of the position markings 9 of the position track 5 of the measuring standard 4. The position-measuring device 3 thus has sensor elements 7 of a fixed size for capturing the digital values, whereby the length of a code position marking 9, and thereby of one bit, is predefined (within certain limits). The assignment of the binary code 1, 2 to the position cannot be changed, so that the position-measuring device 3 is designed to capture a measuring standard 4 with the complete binary code 1.

[0073] For rotational position-measuring devices 3 this means that the radius on which the bit sequence must be located is also determined by the predefined length of a bit 9 and the fixed number of bits 9 in the full binary code 1. If a smaller radius is now to be used, the length of the bits 9 in a complete binary code 1 would become smaller, as a result of which this can no longer be captured correctly by the sensor elements 7, in particular of a given sensor device 6. If, on the other hand, the length of the sensor elements 7 and the length of a bit 9 matched to that on the measuring standard remain unchanged, only a portion of the binary code 1 can be used. According to the invention the possibility is prevented that when code words C are omitted, bit combinations are read out that are indeed present in the complete binary code 1, but are not located at the correct position, and thereby code position within the remaining used region, or are even located within the excluded region. The code positions captured by the sensor elements 7 would otherwise, for example, be non-continuous or even not unique if two code positions with the same encoding were to exist.

[0074] In order now to realize the possibility of being able to deal with a position-measuring device 3 with different measuring standard 4, and in particular different measuring standard 4 with different diameters, by means of an in particular predefined system 3, in which the length of the position markings 9 remains the same, the binary code 1 can be adjusted in such a way that on a smaller measuring standard 4 the binary code 2 is a binary code 2 forming a portion of the first binary code 1, with a second number m of code words C that can be mapped onto the first binary code 1. In this way, a particular portion of the first binary code 1 can be omitted, and a unique code position assignment can nevertheless be achieved. The illustration in FIG. 2 shows by way of example such a binary code 1 of a first measuring standard 4 designed for a number M of code words C with a missing portion 10, wherein this code 1 has separation points T1, T2.

[0075] This shortened code 1 can then be transferred to a second measuring standard 4, in particular of a smaller design, as is shown by way of example in FIG. 3a. The second binary code 2 can in particular then be joined at the separation points T1, T2. As can be seen for example in FIG. 2 and FIG. 3b, a part of the code words C has been removed from the binary code 1; compare, for example, the code words C with the code numbers CN.sub.M 5 to 10. In this way, the same scanner can be used for measuring standard 4 with different diameters.

[0076] The second binary code 2, which represents a partial code of the first binary code 1, is no longer complete, but is also closed in itself, and also, as a shift code, has no discontinuities. This behavior corresponds largely to the behavior of the first binary code 1, and can therefore be treated in a similar manner with little effort in the further processing unit 8.

[0077] According to the invention, the second binary code 2 can be mapped onto the first binary code 1, in particular by means of a predefined mapping rule.

[0078] The mapping is done in such a way that the code positions P.sub.m of the second binary code 2 can be mapped onto the code positions P.sub.M of the first binary code 1. The mapping rule here gives the mapping relationship between P.sub.m and P.sub.M.

[0079] The mapping rule V can, for example, be described by means of the formula

P.sub.M=(m/M)*P.sub.m+P.sub.S

or

P.sub.m=(M/m)*(P.sub.M−P.sub.S)

in the same way. The mapping relationship between P.sub.m and P.sub.M is fixed and unique, so that by means of the specified mapping rule both P.sub.m can be mapped onto P.sub.M and P.sub.M can also be mapped onto P.sub.m. In the initial generation of the second binary code 2 for the respective measuring standard with m<M, the omitted portion of the first binary code 1 is selected in such a way that this results in a fixed and unique mapping relationship. The respective mappings can then be calculated by means of the mapping rule V.

[0080] The mapping rule V contains a scaling using a scaling factor and a position displacement. This is necessary, as some of the positions of the large code disk 4 with M positions are missing when capturing the smaller code disk 4 with m positions. The further processing unit 8, however, preferably expects all the positions of the large code disk 4, while the size relationship must at the same time be given consideration. This is achieved by the mapping.

[0081] The second binary code 2 also comprises unique code words C, each of which is assigned to a unique code position P.sub.m with the code word length L over which the binary codes 1, 2 extend. The code words C of the second binary code 2 here have the same sequence as the code words C of the first binary code 1, with the code words C omitted with respect to binary code 1. The second binary code 2 enables continuous position values, and, as a shift code that is still closed, has no discontinuities. Binary code 2 begins with the code number CN.sub.M 11 from the binary code 1 for the start value S with a new code number CN.sub.m=0, and ends with code number CN.sub.M 4 from the complete binary code 1 at the end position E with the new code number CN.sub.m=25.

[0082] The mapping rule referred to above thus corresponds to a displacement, in particular by a position P.sub.s, of the code positions P.sub.m corresponding to the code words C of the binary code 2, and scaling by multiplication of the physical code positions P, in particular as angular values of the binary code, by the factor M/m or m/M.

[0083] The respective code number CN.sub.m in the table in FIG. 3b corresponds here to the code position P.sub.m=CN.sub.m×360°/m.

[0084] The code numbers CN.sub.m extend from 0 to 25, taking into account the overflow with respect to code numbers CN.sub.m of the complete binary code 1 from CN.sub.M=31 to CN.sub.M=0.

[0085] The table of FIG. 3b, in which the values of CN.sub.M are listet, serves above all for a better understanding of the background to the invention. In the practical realization of the invention, the table according to FIG. 3b does not have to be stored in the sensor device, since the calculation of the position P.sub.m is done by the code conversion illustrated in FIG. 1b, with subsequent mapping.

[0086] As is shown by the exemplary embodiment of FIGS. 3a and 3b with a measuring standard 4 with a scale with a second binary code 2, the second binary code 2 has, according to the present exemplary embodiment, the following bit sequence: 11110 00110 11101 01000 00100 1. This bit sequence is recorded at the code start value S with movement of the measuring standard 4 in the clockwise direction. With a code word length L=5 remaining the same, a total of m=26 unique code words C can be formed with this code 2. As can be seen in the table in FIG. 3b, a unique physical code position P.sub.m with the code word length L spanned by the binary code 2, can thus also be assigned to each unique code word C.

[0087] To map the second binary code 2 onto the first binary code 1, the start value S and the second number m of code words C, or the start value S and the end value E, or the end value E and the second number m of code words C can, for example, be specified. A unique mapping of the second binary code 2 onto the first binary code 1, and thereby a usability of further components of the position-measuring device 3, in particular of the sensor elements 7 on the sensor track 11 and the further processing unit 8, can be achieved in this way. The second binary code 2 can, in particular, have a start position P.sub.S that can be subtracted from the respective code position P.sub.M, in particular as an angular value, to map the second binary code 2 onto the first binary code 1.

[0088] According to the table in FIG. 3b, the code number CN.sub.m=11 corresponds, for example, to the angular value P.sub.M=CN.sub.M×360°/M=11×360°/32=123.75° (with reference to CN.sub.M=0, corresponding to 0°) on the complete measuring standard 4 in FIG. 1, and the start position P.sub.S on the trimmed measuring standard 4 in FIG. 2. The angular resolution is 360°/32=11.25°; the code number CN.sub.M=16 corresponds to 180° on the measuring standard with the complete binary code 1.

[0089] The angular resolution of the trimmed measuring standard of FIG. 2 mapped onto the smaller measuring standard in FIG. 3a is 360°/26=13.85°. With CN.sub.m=0 (corresponding to 0°) CN.sub.m=1 here corresponds to the angle 13.85° and CN.sub.m=13 to the angle 180°.

[0090] The position markings 9 of the second binary code 2 can also be recorded by the sensor device 6, and then transmitted for further treatment to the further processing unit 8. The conversion of the code words C of the first binary code 1 and of the second binary code 2 into code positions P.sub.M can then take place in the further processing unit 8, for example by means of a look-up table and/or other mathematical methods such as, for example, by means of a feedback shift register. The further processing unit 8 comprises a code converter 12 as a function block for this purpose. The code position P.sub.M ascertained in each case in this way can then be processed by the further processing unit 8, and further signals can be generated from it. The further processing unit 8 can consist of digital and/or analogue function and circuit blocks 12, 13, 14, that are used in the same way for the different diameters of the measuring standard 4 and assigned code spaces. Measuring standard 4 with different diameters can thus, for example, be scanned and evaluated with a single hardware realization of the sensor device 6 and the further processing unit 8 as an integrated circuit. In position-measuring devices 3, incremental A/B signals can, for example, be generated as a measure for speed and direction of movement. The mapping of the second binary code 2 onto the first binary code 1 can take place in order to be able to use the same function blocks, i.e. in particular the function blocks of the code converter 12, the function block of the mapper 13, and downstream function blocks 14 as are used for the first binary code 1 for the processing of the second binary code 2.

[0091] The further processing unit 8 can, for example, have the following function blocks 14 that follow the code converter 12 and/or the mapper 13.

[0092] The further processing unit 8 here provides a block that generates incremental signals and/or commutation signals. The further processing unit 8 is furthermore designed as a counter that forms a multi-turn value. In particular, the further processing unit 8 provides an interface such as, for example, BiSS, SPI or the like.

[0093] As already described, the mapper 13 can also be integrated into the code converter 12 and/or into one or a plurality of function blocks 14 that follow the code converter 12.

[0094] The position-measuring device 3 according to the invention can be used both in measuring systems in which a continuous ascertainment of the position is performed by means of a measurement, and/or in counting systems 3.

[0095] With a position-measuring device according to the invention, an absolute position of a position-measuring device 3 can be generated in a simple manner. It is no longer necessary to provide different sensor devices 6 and further processing units 8 for position-measuring devices 3 for different radii of measuring standard 4. By mapping the second binary code 2 with a second number m of code words C onto the first binary code 1 with a first number M of code words C, each of which has a code word length L, the measuring standard 4 can be adjusted to the respective system 3, in particular with a smaller diameter, and the recorded signals thus processed without problems by an existing further processing unit 8. Advantageously the invention can therefore be employed, in particular, in rotary, optical or magnetic position-measuring devices 3, since with a single fixed sensor layout that is designed with L bits, and the sensor elements 7 of which have a fixed length corresponding to the length of the position markings 9, the code words C can be determined in a closed code. As a consequence of this, the respective length of the total code 1, 2, and thereby the diameter of the measuring standard 4, can also be determined. The scaling is done with fewer code words C and thereby smaller diameters of the measuring standard 4, proportional to m/M.

[0096] The flow of the measuring process with a position-measuring device according to the invention for ascertaining the rotary position of the measuring standard is described below in detail once again with reference to FIGS. 4 to 6. FIG. 4 corresponds to FIG. 1a, FIG. 5 corresponds to FIG. 2 and FIG. 6 corresponds to FIG. 3a, wherein position information have been added in each case by example.

[0097] The position-measuring device 3 comprises, according to FIG. 4, a measuring standard 4, a sensor device 6 and a further processing unit 8. A first binary code 1 is present on the measuring standard 4, which can be correspondingly scanned by the sensor device 6. The sensor device 6 is designed for sampling with code words C, and in the present example comprises five sensor elements 7. The sensor device 6 can be integrated onto a chip. A further processing unit 8 is connected to the sensor device 6. This can be integrated onto a common chip together with the sensor device 6.

[0098] The further processing unit 8 comprises a plurality of function blocks, namely a code converter 12 that performs the conversion of the code words into position information, a mapper 13 for taking the mapping relationship into account, and further function blocks 14. The function blocks 12, 13, 14 of the further processing unit can, although not necessarily, be designed as a separate unit. Individual, multiple or all the functions of the function blocks 12, 13, 14 can also be realized in a common unit, for example in a common integrated circuit.

[0099] For the sake of better understanding, a known measuring method is first explained:

[0100] In the exemplary embodiment, the code words C are stored in a table, illustrated in FIG. 1b, for shift code conversion. The code conversion is carried out by the code converter 12, in which the conversion of the table is implemented. Preferably the code conversion is realized by shift registers or using a stored look-up table. Other types of code conversion are, however, possible.

[0101] A corresponding code number CN.sub.M is uniquely assigned to each code word C, and can be used for numbering the code words C. A number M=32 of code numbers CN.sub.M result for the exemplary embodiment.

[0102] The sensor elements 7 of the sensor track 11 scan the binary code 1. In the position of the measuring standard 4 illustrated in FIG. 4, the code word C “01101” is correspondingly scanned, and, in accordance with the code conversion implemented according to FIG. 1b, corresponds to the CN.sub.M value “21”. The corresponding position P.sub.M, which in the exemplary embodiment corresponds to an angular position, is then ascertained, for example computationally, using this CN.sub.M value. The formula given in FIG. 1b can be used for this purpose, according to which P.sub.M=21×360°/32=236.25°. The scanned code word C “01101” thus corresponds to the position P.sub.M=236.25° of the measuring standard 4. This procedure so far does not contain the realization of the invention.

[0103] It is now possible with the invention to achieve that with the same sensor device 6, other measuring standard can also be used, for example because a smaller measuring standard is needed due to the available space, or because only a lower resolution is necessary. The measuring standard 4 with the binary code 1 is therefore to be replaced, for the further explanation of the invention, by a measuring standard 4 with a smaller diameter according to FIG. 6.

[0104] The smaller measuring standard 4 according to FIG. 6 comprises a second binary code 2, which forms an in particular contiguous portion of the first binary code 1. The binary code 2 thus comprises a smaller number of code words C, namely m=26, and this number m of the position device 3 is to be specified when exchanging the measuring standard 4. The sensor device 6 and the further processing unit 8, together with the code converter 12 that carries out the code conversion, are retained, and are not exchanged.

[0105] If the sensor device 6 now scans the second binary code 2, then in the position of the measuring standard 4 illustrated in FIG. 6, the code word C “10111” will accordingly be scanned. With the unchanged, stored code conversion according to FIG. 1b, the scanned code word C “10111” corresponds to the value CN.sub.M “23”. Using this value, a position P.sub.M can be ascertained, analogously to the procedure described previously, according to which P.sub.M (CN.sub.M=23)=23×360°/32=258.75°.

[0106] Since the position P.sub.M of the angular position corresponding to the code word C “10111” ascertained in this way corresponds, however, to the position on a larger measuring standard 4 according to FIG. 4 with the first binary code 1, the position P.sub.M ascertained from the code conversion according to FIG. 1b still has to be mapped by the mapper 13 onto the actual position P.sub.m.

[0107] In the present example, this is done by means of the mapping rule P.sub.m=M/m (P.sub.M−P.sub.S). M/m here corresponds to a scaling factor that results from the different number of code words C, namely M=32 and m=26. The position P.sub.S corresponds to the position displacement of the measuring standard 4 of FIG. 6 as compared with the measuring standard 4 of FIG. 4, since, due to the shortening of the code, a different alignment of the zero position of the smaller measuring standard has occurred.

[0108] The number M is known to the further processing unit 8. The mapper 13 can, for example, read M from the stored code conversion, or M can be stored directly as a numerical value in the mapper 13.

[0109] The start position P.sub.S (FIG. 5) can, for example, be ascertained analogously to the ascertainment of the code position P.sub.M, for example using P.sub.S=S×360°/M. The start value S must accordingly be specified when exchanging the measuring standard for this purpose. It is, however, also possible to specify the end value E and/or the position displacement P.sub.S directly.

[0110] For the exemplary embodiment illustrated in FIG. 6, a scaling factor of M/m=32/26=1.231 and a position of P.sub.S=11×360°/32=123.75° (FIG. 5) thus results on the trimmed measuring standard. For mapping the position P.sub.M=258.75° onto the position P.sub.m it therefore follows that P.sub.m=32/26×(258.75°−123.75°)=166.154°. This corresponds to the actual position that is to be ascertained of the shortened measuring standard 4 according to FIG. 6 related to the new zero position P.sub.m=0° with the code “10011” corresponding to the code number CN.sub.M=11 from the code table in FIG. 3b.

[0111] The mapper 13 is configured so that a cyclic overflow can be ascertained and taken into account. The binary codes 1, 2 of the exemplary embodiment is a closed code, so that to apply the mapping rule it is necessary, when forming the difference “P.sub.M−P.sub.S”, to bear in mind that this term must always be greater than or equal to “0”. In the event that the difference term is smaller than 0, an additional 360° must be added to it before the scaling. Were the sensor device 6 with the measuring standard 4 and with binary code 2 to scan, for example, the code word C “00001”, then it follows from the stored code conversion according to FIG. 1b that CN.sub.M=1. With position P.sub.M=11.25° the result for the difference term P.sub.M−P.sub.S=−112.5°, which is smaller than “0”. Due to the cyclically closed nature of the code, the position P.sub.m=M/m (P.sub.M−P.sub.S+360°)=304.615° is therefore ascertained.

[0112] In the previously described exemplary embodiment, the positions P.sub.M and P.sub.m were given as angular positions. It is also possible to use other dimensions of the position. The position dimension used can, in particular, be matched to the function blocks 14 of the further processing unit 8. Other position dimensions can accordingly be used provided, for example, the further processing unit 8 does not require angle information. The position dimension can, for example, also be an incremental value. It is in particular possible that the position dimension has the format of the code number CN itself. An example is now to be presented for this case:

[0113] Analogously to the procedure described previously, the code word C “10111” is first scanned by the sensor device 6 on the measuring standard 4 according to FIG. 6, and corresponds, in the code conversion according to FIG. 1b, to the CN.sub.M value “23”. Now, however, an angular dimension is not used as the dimension for the position P.sub.M, but the format of CN.sub.M itself, where the identifier P′M is used below as a real numerical value purely for the purpose of clarification. The CN.sub.M value at this position thus corresponds to the position P′M of a measuring standard 4 according to FIG. 4 with the first binary code 1, and must still be mapped to the actual position.

[0114] The mapping takes place in the same way in the mapper 13 through the mapping rule P′.sub.m=M/m (P′.sub.M−P′.sub.S) already explained, wherein the position P′ expressed as the CN value is again here scaled and displaced. While the scaling factor M/m results from the different numbers M, m of code numbers CN, the displacement P′.sub.S corresponds to the start value S. The start value S can be specified directly. It is equally possible to specify the end value E and to ascertain the start value S from the difference between the numbers M and m.

[0115] For the CN.sub.M value “23” assigned to the code word C “10111”, a position value of P′.sub.m=32/26×(23−11)=14.77 thus results. This corresponds to the actual position of the measuring standard 4 according to FIG. 6 that is to be ascertained, while the format of the code numbers itself is chosen as the position dimension. This value P′.sub.m can be processed by the further processing unit 8, in particular by the function blocks 14.

[0116] The example makes it clear that the mapping can be independent of the dimension of the position information P. Yet more position dimensions could accordingly be used. The position dimensions are advantageously chosen such that they can be processed by the further processing unit 8.

[0117] The same sensor device 6 can, of course, also be employed for further measuring standard 4 with an arbitrary number m≤M of code words. The respective design of the measuring standard 4 is taken into account in the mapper 13, for which purpose only a few parameters of the measuring standard 4 that is to be used have to be specified to the mapper 13, in particular the parameters m and P.sub.S, or other information from which these parameters can be ascertained, such as, for example, S and E.

[0118] The further processing unit 8, with the implemented mapper 13, also of course functions with the measuring standard 4 of FIG. 4, where in this case M=m, P.sub.s=0 and therefore P.sub.m=P.sub.M.

[0119] The position device 3 according to the invention, through the specified, fixed and unique mapping relationship between the first binary code and the second binary code 2, or between the positions P.sub.M and P.sub.m, thus enables the use of different measuring standard 4 with different binary codes 1, 2 while retaining the hardware in use, such as, in particular, the sensor device 6 and the further processing unit 8, and in particular the code conversion implemented once, so that cumbersome and expensive refitting of the position-measuring device 3 is not required.

[0120] The design of the measuring standard 4 is selected according to the invention in such a way that the second binary code 2 is mapped onto the first binary code 1. The mapping relationship is fixed and unique, so that this mapping relationship can be used to ascertain the position that is to be measured.

REFERENCE SIGNS

[0121] 1 First binary code [0122] 2 Second binary code [0123] 3 Position-measuring device [0124] 4 Measuring standard [0125] 5 Position track [0126] 6 Sensor device [0127] 7 Sensor elements [0128] 8 Further processing unit [0129] 9 Position markings [0130] 10 Portion [0131] 11 Sensor track [0132] 12 Code converter [0133] 13 Mapper [0134] 14 Function blocks [0135] M First number of code words [0136] m Second number of code words [0137] C Code words [0138] L Code word length [0139] CN.sub.M Code number in the first code table [0140] CN.sub.m Code number in the second code table [0141] S Start value of the code [0142] E End value of the code [0143] P.sub.M Code position in the first binary code [0144] P.sub.m Code position in the second binary code [0145] P.sub.S Start position [0146] B Direction of movement [0147] T1, T2 Separation point [0148] V Mapping rule