Abstract:
A transducer, a method and a coding pattern for determining a kinematic measurable variable are disclosed. A transducer comprises a first device part which is moveable in or through a corresponding device for oil or natural gas production and a second device part which is stationary relative to said first device part. To detect both the directions of movement and the respective position in a simple constructional and inexpensive way without the need for return movement up to ends of the range of movement, the first and/or second device part comprises a coding pattern which is changing along a direction of movement and of which position-specific patterns can be scanned by a scanning means which is arranged on the respective other device part. By scanning such a specific coding pattern during mutual relative movement of said objects or device parts a corresponding scanning signal can then be converted by an evaluation unit into a kinematic measurable variable. The corresponding coding pattern comprises a plurality of single patterns wherein neighboring single patterns differ from one another by at least one characteristic feature and/or said single pattern has at least one characteristic feature that is changing in the direction of movement.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a transducer for at least one kinematic measurable variable, such as position, speed, or the like, particularly in devices for oil and natural gas production, comprising a first device part which is movable in or through the device, and whose kinematic measurable variable is to be determined, and a second device part which is stationary relative to the first device part. Furthermore, the invention relates to a method and a coding pattern for determining such a kinematic measurable variable.  
         [0002]     Such transducers serve, for instance, to determine the position during displacement of the movable device part relative to the stationary device part. With the displacement of the parts relative to one another, the position of a shut-off device, a blow-out preventer, a rotary adjustment device, a valve, a throttle, or the like, is detected and represented at a desired place as positional information. The corresponding devices are used in oil and natural gas production for transportation along transportation pipelines, for changing the transportation capacity of the transportation pipelines, for shutting off the transportation pipelines in case of emergency, for adding chemicals to the transportation lines in a controlled way, or the like. At any rate, exact knowledge of the relative position of movable device part and stationary device part is required.  
         [0003]     So far the position has e.g. been determined by assigning a scale to a spindle, a piston, or another movable device part, and by reading the corresponding position of the movable device part relative to the stationary device part from the scale. A further known possibility of determining the position is a potentiometer or linear resistor relative to which a contact is adjusted upon movement of the movable device part, so that the detected resistance is changed.  
         [0004]     Finally a further possibility of determining the position is known where slits, or the like, are arranged as coding patterns on a scale at the same linear distance. These are sensed and counted to determine corresponding positions. Instead of a linear arrangement of such slits, a rotary disk is already known with slits arranged at a constant distance in circumferential direction, the slits being also sensed by light detectors, or the like, and then counted.  
         [0005]     These known transducers have the disadvantage that in addition to the scanning of the similar and equally spaced subdivisions on the corresponding scale, for instance slits in an encoder disk, the corresponding subdivisions must be summed up in addition to the scanning operation to obtain corresponding information on the position. Furthermore, in the prior-art transducers it is not immediately apparent in which direction the movement actually takes place since it is not readily apparent, for instance, in the case of a straight movement whether the movement is to the left or to the right side. This applies by analogy to a rotating encoder disk in which the rotational direction is not easily detectable by the transducer.  
         [0006]     A further drawback is that e.g. upon failure of an electronic means of the transducer the relative position between movable device part and stationary device part can no longer be detected and that a movement up to an end of the possible relative motion range is required to carry out the corresponding position determining operation once again.  
         [0007]     U.S. Pat. No. 4,224,603 A discloses a device for locating the position of a moveable component with a binary code and five transducers. According to this document, it is possible to obtain an absolute coded position-location, wherein different displacements are shifted by one bit. The coded bit data is, for example, arranged on some kind of toothed rack and is realized by corresponding activation zones. Different positions or displacements are detected by scanning such coding pattern.  
         [0008]     U.S. Pat. No. 5,576,535 A discloses a position detection system with two-bit coding by two types of markings arranged in a pseudo-arbitrary way. The corresponding markings are provided on a piston rod moveable along a cylinder to which a detector is assigned. Groups of these markings are disposed in such a way that they partially overlap, such that each two successive groups have a different number of markings in common. A scanner unit used for scanning the markings of such a group can be a LED.  
         [0009]     EP 0947 805 A is directed to an apparatus for determining the position of a moveable mechanical element. A marking is provided on a piston rod, wherein such markings may comprimise code elements as a unique part of a pseudo-random binary sequence. The different code elements are optically readable.  
         [0010]     U.S. Pat. No. 5,739,775 A is directed to a digital input and control device used for converting aboslute angular or linear mechanical positions to a digital output. A corresponding encoder with conductive and non-conductive rotor segments is scanned by a number of contact elements. The different rotor segments are arranged in a sequence, such that a five-bit output code is realized, which is said to be a gray code sequence.  
       BRIEF SUMMARY OF THE PREFERRED EMBODIMENTS  
       [0011]     It is therefore the object of the present invention to improve a transducer, a method and a coding pattern such that both the direction of the movement and the respective position can be detected in a simple, constructive and inexpensive way without the need for a return movement up to ends of the range of movement.  
         [0012]     This object is achieved with the features of claim  1 .  
         [0013]     Due to the change in the coding pattern in the direction of movement of one device part and the various position-specific single patterns, the actual direction of the movement can be detected in an easy way. It is known in which way the coding pattern is changing, and it can therefore be detected in an easy way by scanning the coding pattern in which direction the movement takes place. Moreover, since the corresponding single patterns of the coding part are position-specific, it is even possible in a simple way and upon renewed start after a temporary failure of a corresponding electronic means, or the like, of the transducer that the current relative position is detected between first and second device part. At the most the first device part would have to be shifted to such an extent that the closest single pattern can clearly be sensed again by the scanning means. At any rate, a return movement of the first device part up to an end of the range of movement is not needed for determining the position again from said place or for determining the corresponding kinematic measurable variable. According to the invention the pattern comprises rising and/or falling edges succeeding one another in the direction of movement. These rising and falling edges constitute the position-specific structuring of the conductivity pattern, thereby permitting a definite determination of the relative position of coding pattern and scanning means.  
         [0014]     Particularly in corresponding devices for oil and natural gas production, such a minimal movement of the first device part for the renewed determination of the corresponding kinematic measurable variable is of advantage because in this way the corresponding devices need not be moved back fully, e.g., in the case of a valve into a closing position or an opening position. Instead, a minimal movement is only needed for sensing the next single pattern.  
         [0015]     Finally, it is here also of advantage that the scanned subdivision of a corresponding scale need not be summed up. Instead of this, the relative position between first and second device part is clearly determined by each position-specific single pattern.  
         [0016]     According to the invention, the single patterns are formed from a position-specifically differently structured pattern that is arranged in the direction of movement. Such a pattern is e.g. formed by a conductive metal, such as copper or the like, which is arranged in a specific region having a specific structure. The structure is here chosen such that it is specific of the respective position of the conductivity pattern. An example of such different conductivity patterns would be different geometrical figures, or the like, which can be scanned accordingly by the scanning means, whereby the corresponding position can be determined.  
         [0017]     To be able to determine the position in an easy and definite way, at least neighboring edge rises may have different absolute values. This means that e.g. in the case of a conductivity pattern having first a rising and then a falling edge in the direction of movement, the corresponding edge rises are different in their absolute value. This applies by analogy to neighboring conductivity patterns in which e.g. both the rising and the corresponding falling edges have different absolute values in the edge rise with respect to the neighboring conductivity pattern and also with respect to the edge rises of each conductivity pattern.  
         [0018]     There is the possibility that the corresponding conductivity pattern has an approximately straight lower border extending in the direction of movement, from which the different edges extend each at one side. To improve the measured signal, it is however of benefit when the conductivity pattern is made symmetrical to a horizontal plane in the direction of movement. This means that the corresponding edges extend at both sides relative to said horizontal plane and in symmetry therewith.  
         [0019]     The conductivity patterns, however, may also have different rising and/or falling edges at both sides relative to the above-mentioned horizontal plane.  
         [0020]     In a simplified embodiment, it may be sufficient when the conductivity pattern is made substantially symmetrical to a line perpendicular to the direction of movement. This means that the conductivity patterns in the direction of movement are repetitive at the left and right side to said perpendicular line, but in a different, particularly opposite, order.  
         [0021]     Different methods are possible for forming the corresponding conductivity patterns. For instance, the conductivity pattern could be detached from a metal foil and then applied to a corresponding pattern carrier. A simple production can be seen in the measure that the coding pattern and the different conductivity pattern, respectively, can directly be produced by etching, or the like. Such production methods are e.g. used in the manufacture of printed circuit boards.  
         [0022]     To be able to carry out the scanning of the single patterns in a faster way, the scanning means may comprise a number of single scanning elements. Depending on the number of said single scanning elements, the corresponding single pattern can be sensed partly or also completely in one scanning operation.  
         [0023]     Scanning means and single pattern can preferably be assigned such that an extension of the scanning means or the single scanning elements in the direction of movement substantially corresponds to a length of each single pattern of the coding pattern. As a result, a single pattern is also directly sensed by each single scanning element without e.g. a single pattern being sensed by neighboring single scanning elements or without a plurality of single patterns being sensed by a single scanning element at the same time. This increases the resolution in the detection of the kinematic measurable variable and each single pattern can be reliably scanned at the same time.  
         [0024]     To enhance, if necessary, the resolution by single patterns and scanning elements, n single patterns of a coding pattern may have assigned thereto n+1 or n−1 single scanning elements. As a result, either the scale with the single pattern or that with the single scanning elements is a vernier scale which is shorter by one respective element. For instance, if 10 single patterns are provided each coding pattern, the vernier scale of the single scanning elements may comprise nine single scanning elements. The ten single patterns have the same length as the nine single scanning elements, so that e.g. the first single pattern is shifted by 1/10, the second by 2/10, etc., each with respect to the single scanning element.  
         [0025]     It is possible to form a single pattern by at least one single bit. For a complete sensing of the single pattern without a displacement of the scanning means relative to the single pattern, and in order to accelerate the scanning operation, a single scanning element may be assigned to each single bit of a bit pattern group (data word width) as the single pattern group. The whole data word width and thus the kinematic measurable variable is thereby sensed in one scanning operation.  
         [0026]     Furthermore, the resolution of the detection of the kinematic measurable variable can be enhanced when the bit pattern groups are shifted in the direction of movement by one respective single bit relative to one another. This means that the next position-specific bit pattern group is sensed by shifting the scanning means relative to the bit pattern by one single bit only, so that the resolution is substantially defined by the width of the single bit and the single scanning element, respectively.  
         [0027]     The coding pattern can be realized in different ways in the case of coding patterns in the dual system, only two different features or states have to be assigned to the single bits. The corresponding features/states can be detected by the scanning means.  
         [0028]     An example of two states of such a type for corresponding single bits or single patterns is that the corresponding coding pattern is formed by recesses and/or elevations. This means that single bits may differ from one another by different depths of the recesses, heights of the elevations, or the like. Recesses and elevations may also alternate, and the recesses may each have the same depth and the elevations the same height in this instance.  
         [0029]     Another possibility of realizing such a bit pattern are regions of different conductivity or regions with different reflectivity.  
         [0030]     In regions with different conductivity, a single scanning element may e.g. comprise at least one coil. When an a.c. voltage is applied to said coil, the coil exhibits different damping characteristics in response to the conductivity of the corresponding detected regions, each of which forms a single pattern. This applies by analogy to single patterns of different recesses and/or elevations because said elevations and recesses may also have different impacts on a coil supplied with a.c. voltage.  
         [0031]     To be able to determine the kinematic measurable variable in a redundant way, two scanning means may be arranged, particularly in direct vicinity in the direction of movement. For instance, when one of the scanning means fails, the instantaneous position and a change in the position can be detected by the corresponding other scanning means. Especially for the scanning of the whole range of movement of the two device parts, it is advantageous when the scanning means are arranged in direct vicinity.  
         [0032]     Scanning means and coding patterns are arranged between the two device parts in accordance with the direction of the relative movement. For instance, when the direction of movement is straight, coding pattern and scanning means also extend along a straight line.  
         [0033]     Other possibilities regarding directions of movement are a helically extending or a substantially circularly extending direction of movement. Coding pattern and scanning means can each be arranged accordingly.  
         [0034]     A further possibility of forming a coding pattern may be seen in the measure that the pattern is formed along a coding pattern carrier which is fastened to a device part in a particularly detachable manner. The coding pattern may be designed on the corresponding coding pattern carrier in accordance with the respectively desired resolution. A coding pattern can be replaced by a finer or coarser coding pattern thanks to the possibility of exchanging the coding pattern carrier.  
         [0035]     To supply specifically the scanning means with electrical power and to transmit corresponding signals of the scanning means to an associated evaluation means, a corresponding electrical line may be passed from the scanning means along a line bore.  
         [0036]     For the detection of kinematic measurable variables during a rotational movement, it may be of advantage when the coding pattern comprises single patterns arranged along a circular path. For instance, upon rotation of the movable device part, the single patterns can then be scanned along the circular path on the stationary device part via a correspondingly co-rotated scanning means. It is also possible that the single patterns are arranged on the movable or rotary device part and that the scanning means is provided accordingly along the circular path of the single patterns on the stationary device part.  
         [0037]     When the coding pattern is arranged or at least assigned relative to the movable device part, the coding pattern may comprise single patterns arranged along a circumference of a disk. The single patterns, in turn, may be formed by regions of different conductivity, of different reflectivity, with recesses and/or elevations, or the like. The corresponding single scanning elements of the scanning means on the stationary device part are here assigned to the circumference of the disk.  
         [0038]     Instead of a scanning operation from a radial direction, a scanning operation may be carried out essentially in a direction perpendicular to the disk plane with a corresponding arrangement of the coding pattern. The scanning operation can e.g. be carried out in that the coding pattern comprises single bits slotted in the disk as single patterns. It is also possible to design the slits with a width increasing in radial direction. Especially in this connection, it can be regarded as an advantage when the single scanning elements are radially adjustable. Thanks to the radial adjustment a single scanning element can exactly be assigned to the region of the slit-shaped single bit which in its extension in rotational direction corresponds to the corresponding extension of the single scanning element.  
         [0039]     Depending on the respective requirement, a corresponding coding pattern may comprise a corresponding number of single bits. For instance, the coding of the position can take place by way of 4, 5, 6, 7 or more single bits per coding pattern. The number of the single scanning elements of the scanning means defines the number of the single bits of a coding pattern. This means that preferably four single scanning elements are used in the case of a four-bit coding.  
         [0040]     To control and, optionally, check the movements of the first device part relative to the second device part for at least a certain period of time, the transducer may comprise at least a storing means for storing measured signals of the scanning means in response to the position.  
         [0041]     Favorably, signals of at least a number of single scanning elements can optionally be stored here in dependence upon the position. The number of the single scanning elements is here preferably identical with the number of the single patterns of a coding pattern.  
         [0042]     To obtain information on the whole range of movement, initial measured-signal information may be storable in the storing means at least once for a total range of movement of the scanning means and/or at least a number of single scanning elements.  
         [0043]     To improve the resolution in the measurement of the kinematic measurable variable, the transducer may comprise a comparing means for comparing the initial measured-signal information with current measured-signal information. The corresponding current measured-signal information can be used by way of comparison with the initial measured-signal information for determining exactly to which region of the initial measured-signal information the current measured-signal information corresponds. The relative position between movable device part and stationary device part can thereby be determined with higher accuracy than the resolution by the single patterns. The corresponding resolution depends on the resolution of the corresponding measured-signal information. When said resolution is correspondingly high, a measurement and evaluation of the current measured-signal information cap e.g. be carried out substantially in analog form or at least in quasi analog form. This can considerably enhance the resolution by the single patterns.  
         [0044]     Thanks to the above-mentioned higher resolution it is further possible to dispense with the displacement of the first device part in case of temporary failure of a corresponding electronic means, or the like, so as to sense the present relative position between first and second device part again. The above-described movement of the first device part for the definite detection of the closest kit pattern group or single pattern in case of renewed start is thus not necessary either. Instead of this, one obtains an absolute-value determining means for each position of first and second device part relative to one another, which upon a renewed start, e.g. after failure of the electronic means, directly permits the determination of the corresponding relative position with high accuracy.  
         [0045]     To lose no information during the determination of the kinematic measurable variable during comparison of the measured-signal information for the exact determination of the position, at least the last current measured-signal information may be stored after its acquisition until its replacement by subsequent current signal information.  
         [0046]     To enhance the resolution of the determination of the kinematic measurable variable in a simple way, scanning means and/or coding patterns may be designed such that they can be replaced. This can e.g. be accomplished by replacing the above-mentioned scanner carrier or coding pattern carrier. In connection with the arrangement of two scanning means, the coding pattern can be replaced by a coding pattern having twice the number of single patterns. These are then sensed by the two scanning means at the same time for determining the kinematic measurable variable.  
         [0047]     To supply scanning means, in particular, including a number of single scanning elements, with electrical power in a safe and simple way, a particularly pressure-resistant multiple cable passage may be provided for the electrical connection of the scanning means. This passage is preferably arranged in the stationary device part and serves the simultaneous electrical supply of all single scanning elements of the scanning means.  
         [0048]     It should additionally be noted that the initial measured-signal information can also be determined by a few single scanning elements only, said information being compared with corresponding current measured-signal information of the same single scanning elements. For reasons of redundancy corresponding measured-signal information of all scanning elements may be compared.  
         [0049]     The single patterns may be characterized by two possible states (features). It is also possible that the single patterns comprise more than two states and that all of said states can be detected by corresponding single scanning elements. Of course, it is also possible to determine other kinematic measurable variables in addition to the position, e.g. speed and acceleration. Appropriate electrical means for differentiating the position values in time, and thus the sensed distance covered, can be assigned to the transducer.  
         [0050]     To sense the different conductivity patterns of the coding pattern with the help of a corresponding scanning means in an easy and fast way and to be able to detect the corresponding kinematic measurable variable, such as position, speed, or the like, the scanning means may comprise a number of coils as single scanning elements which are arranged one after the other particularly in the direction of movement. Advantageously, each of the single scanning elements may be designed as a coil which is wound substantially helically in a plane. This coil can be produced by analogy with the conductivity pattern by etching, or the like, directly, e.g., on the corresponding scanner carrier. Simple examples of such coils wound in a plane are e.g. square coils.  
         [0051]     It is possible to arrange and form not only the coil, but also the conductors powering the same, on a corresponding surface of the scanner carrier, it is here also possible that the conductors for powering the coil are arranged on both surfaces of the scanner carrier and connected by the scanner carrier to the coil which is e.g. only arranged at one side.  
         [0052]     To obtain a reliable measurement signal with adequate noise ratio, two scanner carriers with corresponding coils and conductors may e.g. be assigned to one pattern carrier. This can be implemented in an embodiment which can easily be realized by the measure that a pattern carrier is movably supported between two scanner carriers relative to said carriers.  
         [0053]     in this instance, the two scanner carriers can be designed to be separated from each other. The corresponding measurement signals of the single scanning elements must here be combined with one another to scan the corresponding pattern carrier at both sides for determining the corresponding kinematic measurable variable.  
         [0054]     It is however also possible that the scanner carrier is substantially designed as a carrier foil with central piece and two carrier arms projecting therefrom, the central piece being designed as an electrical connection section and the carrier arms comprising scanning elements and conductors and being adapted to be arranged at both sides relative to the pattern carrier. Such a carrier foil can be produced easily as a scanner carrier, and similar techniques as in the case of printed circuit boards or other electronic components can here be employed again.  
         [0055]     To simplify the construction of the scanning means, it is possible to connect the scanning coils in parallel.  
         [0056]     To improve the resolution of the transducer in this connection, an extension of all scanning coils in the direction of movement and/or in a direction perpendicular thereto can be greater than the maximum length or height of a single pattern, so that the scanning coils can be assigned to a rising and or a falling edge of each single pattern or of directly neighboring single patterns. This avoids a situation where e.g. all single scanning elements in a specific relative position of scanning elements and single patterns only measure a falling or a rising edge of a single pattern..  
         [0057]     Production can here be simplified further when the height or amplitude of all single patterns, i.e. the corresponding conductivity pattern, is the same.  
         [0058]     According to the method the above-mentioned object is achieved by the features of patent claim  37 .  
         [0059]     The method according to the invention is e.g. characterized in that the scanning means scans, with a number of scanning coils as the single scanning elements, at least an edge that is rising and falling relative to the direction of movement, the edge pertaining to one or two single patterns made from a conductive material. Said single patterns form in particular a conductivity pattern which has a position-specific structuring on account of said rising and falling edges.  
         [0060]     In this instance, too, the scanning operation can be performed at both sides with respect to the coding pattern.  
         [0061]     To determine the kinematic measurable variable in a fast way, the scanning means can scan each single pattern of the coding pattern singly and successively. Depending on the number of the single patterns pertaining to one single pattern group, the result of the scanning operation is combined for this number of single patterns, whereby the scanning of the single pattern group is achieved.  
         [0062]     If the scanning operation is to be accelerated further, a scanning means can also scan all of the single patterns of a single pattern group at the same time.  
         [0063]     it is self-evident that the single patterns must be scanned in some way or other. The features or states of a single pattern may e.g. serve the scanning operation. man embodiment, the single pattern may e.g. comprise two different physical or corporeal features in an alternative way. An example of such corporeal features is a recess or elevation in the movable or stationary object. Said corporeal features can be detected by corresponding configurations of the scanning means. The design of the corporeal features is also possible on the stationary object, the scanning means being arranged on the respectively other object. It is also possible to provide both single patterns and scanning means on both objects, whereby a redundant determination of the kinematic measurable variables is possible in an easy way.  
         [0064]     In one embodiment, each single pattern may also have e.g. two differently electrically conductive states as an alternative. This means that the coding pattern consists of differently electrically conductive single patterns.  
         [0065]     In yet another embodiment the single patterns may differ in their magnetic properties.  
         [0066]     It is not necessary to code a positioned-based single pattern group by three, four, five, six, seven, eight or more single bits as single pattern.  
         [0067]     The respective width of a single pattern may be relatively small so that the resolution of the kinematic measurable variable can be increased accordingly.  
         [0068]     To improve the resolution in the measurement of the kinematic variable, a comparing means may compare current measured-signal information of the scanning means with the total measured-signal information for determining transitions, in particular, between the s ingle patterns. The relative position between movable object and stationary object can thereby be detected with higher accuracy than the resolution by the single patterns. This corresponding resolution is related with the resolution of the corresponding measured-signal information. If said resolution is correspondingly high, a measurement and evaluation of the current measured-signal information can e.g. be carried out in a substantially analog form or at least in a quasi analog form. This considerably enhances the resolution by the single pattern.  
         [0069]     Furthermore, the invention relates to a corresponding coding pattern according to claim  45 , specifically for determining a kinematic measurable variable, for instance for determining the position, the coding pattern comprising a plurality of single patterns, wherein each single pattern is formed from an in particular electrically conductive material with edges that are rising and/or failing in its direction of extension corresponding to the direction of movement of one device part mentioned above. On account of the edges that have different lengths and are rising or failing in different ways, one obtains the position-specific structure.  
         [0070]     To distinguish different single patterns in an easy way in this connection, the edge rises of one and/or neighboring single patterns may have different absolute values.  
         [0071]     For simplifying the generation of the corresponding single patterns, the heights or amplitudes of all single patterns may be the same in a direction perpendicular to the direction of movement.  
         [0072]     To provide the single patterns in a simple way, the corresponding coding pattern may be formed on a pattern carrier extending substantially in the direction of movement. The generation of the corresponding single patterns and thus of the whole coding pattern can be simplified in that said pattern is produced on the pattern carrier by etching, or the like. Corresponding manufacturing methods are e.g. also known for conductors in printed circuits or in printed circuit boards.  
         [0073]     Such a coding pattern can also be used in a different way for determining a kinematic measurable variable. For instance, it can clearly mark specific positions along an object, each corresponding single pattern having assigned thereto a specific positional region along the object. Thanks to this positional assignment, a definite encoding of such a position is carried out at the same time, so that it can be used for the assignment of a further object to the object provided with the coding pattern. Further uses for such a coding pattern are obvious.  
         [0074]     It should further be noted that several coding patterns can also be arranged one after the other if the successive coding patterns are distinguished by a further characteristic feature. For instance, a different color of the successive coding patterns could be a distinctive criterion. In another embodiment, the single patterns of a coding pattern might e.g. be distinguished by different corporeal features whereas the single patterns of a further coding pattern might differ e.g. in their conductivity, their magnetic properties or in another detectable characteristic feature. Likewise, there is the possibility that such coding patterns are not arranged one after the other, but are offset relative to each other, whereby e.g. the resolution can be enhanced in an easy way in comparison with only one coding pattern. A possibility of such an offset of two coding patterns relative to one another is the gapwise registration of two coding patterns. This idea can also be transferred to three, four or more coding patterns.  
         [0075]     Various possibilities exist for marking the single patterns as to their informative content. For instance, each single pattern might have assigned thereto specific variable features or states of a body or partial body, with the kinematic variable of the body or partial body having to be determined. Examples of such specific features or states are elevations/recesses, different reflectivity, different electrical conductivity, different magnetic properties, different color, etc. The corresponding features or states can be scanned by a corresponding scanning means and then converted by an evaluation means into a corresponding kinematic measurable variable.  
         [0076]     The single patterns forming the coding pattern can be arranged in different ways, depending on the requirements. A linear, circular or also helical arrangement is possible.  
         [0077]     It is known that a decimal value can clearly be assigned to each single pattern group consisting of bit-like single patterns. This means that the assignment in both directions is so clear that exactly one decimal value is assigned to each single pattern group and exactly one single pattern group is assigned to each decimal value. The single pattern groups are coded in analog form.  
         [0078]     An example of such a coding of the single pattern is a binary single pattern. The coding pattern can be composed of different numbers of single patterns, said number depending, inter alia, on the type of coding of the coding pattern and the number of the features or states that are possible for a single pattern. In one embodiment, the single pattern has 2″ single bits with n as the natural number and n single bits per single pattern group. For instance, when n=4, 16 single patterns are used, and single pattern groups of four single patterns each. Since each single pattern group is possibly obtained by displacement by only one single bit from the respectively preceding or succeeding single pattern group, 16 single pattern groups are obtained in this way. Like in a binary system, a decimal value of 0 to 15 can clearly be assigned to each single pattern group, so that 16 different position values can be scanned. As has already been stated above, intermediate position values due to transitions between the single patterns can also be detected. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0079]     Advantageous embodiments of the present invention will now be explained in more detail with reference to the figures which are attached to the drawing, and of which;  
         [0080]      FIG. 1  is a longitudinal section through a device with a transducer;  
         [0081]      FIG. 2  is a longitudinal section, by analogy with  FIG. 1 , with a second embodiment of a transducer;  
         [0082]      FIG. 3  is a longitudinal section through a further device with a third embodiment of a transducer;  
         [0083]      FIG. 4  shows a fourth embodiment of a transducer;  
         [0084]      FIG. 5  is a view showing a detail “X” of  FIG. 3  without a redundant type of the transducer;  
         [0085]      FIG. 6  shows two further embodiments of a transducer in connection with an encoder disk;  
         [0086]      FIG. 7  shows two further embodiments of the transducer in connection with a slotted encoder disk;  
         [0087]      FIG. 8  shows two further embodiments of the transducer in connection with a rotating means;  
         [0088]      FIG. 9  is a side view of the embodiments according to  FIG. 8 ;  
         [0089]      FIG. 10  gives an example of different coding patterns for determining the position in an embodiment of the transducer;  
         [0090]      FIG. 11  shows the total movement information sensed by a single scanning element of a scanning means;  
         [0091]      FIG. 12  shows a sketch for explaining the scanning means and coding patterns;  
         [0092]      FIG. 13  gives a further example of a coding pattern with five binary single patterns in one single pattern group;  
         [0093]      FIG. 14  shows a serially arranged coding pattern according to  FIG. 13 ;  
         [0094]      FIG. 15  is a top view on a coding pattern according to the invention with differently structured conductivity patterns as single patterns;  
         [0095]      FIG. 16  is a top view on a scanning means according to the invention assigned to the coding pattern according to  FIG. 15 ;  
         [0096]      FIG. 17  is an enlarged view showing a detail “X” of  FIG. 16 ;  
         [0097]      FIG. 18  is a perspective top view on a pattern carrier displaceably supported between two scanner carriers according to one embodiment of the invention;  
         [0098]      FIG. 19  is a basic illustration of the assignment of conductivity patterns according to  FIG. 15  and single scanning element according to  FIG. 16 ;  
         [0099]      FIG. 20  is a top view on a further embodiment of a scanner carrier with single scanning coils according to the invention; and  
         [0100]      FIG. 21  is a sketch for illustrating the signals of the various single scanning elements or scanning coils according to  FIG. 16 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0101]      FIG. 1  shows a longitudinal section through a device  2  for oil and natural gas production with a first embodiment of a transducer  1  according to the invention. The device  2  comprises a piston  24  which can be pushed out of a cylindrical housing  43 , as a movable first device part  3 . Housing  43  with a further part mounted thereon forms a stationary second device part  4 . The piston  24  is displaceably supported within the housing  43 . The housing comprises an inlet  44  and an outlet  45  for a pressurized fluid. When pressurized fluid is supplied to the inlet  44 , the piston is displaced in the direction of movement  5  to the right in  FIG. 1 . The movement is here carried out in the longitudinal direction  14  of the device  2 .  
         [0102]     At its free end  42 , for operating a valve, a rotary adjustment device, a blow-out preventer, a throttle, or other means for oil and natural gas production, the piston  24  is movably connected thereto.  
         [0103]     At least in its section arranged in housing  43 , the piston  24  has an inner bore  23  with a corresponding inner wall  22 . A scanner carrier  28  is inserted into said inner bore  23 . The scanner carrier  28  extends in coaxial direction relative to the inner bore  23 . The scanner carrier  28  extends from one end  60  of the housing  43  in the longitudinal direction  14  of the device  2 . A line bore  30  within the scanner carrier  28  communicates with a line passage  46  at an end facing the housing end  60  for laying electrical connection lines  29  through line passage  46  and line bore  3 D between a scanning means  8  arranged at the free end  27  of the scanner carrier  28  and an evaluation and control means of the transducer  1  arranged remote from the device  2 .  
         [0104]     In  FIG. 1  the control and evaluation means  61  comprises a comparing means  38 , a storing means  36 , a display means  41  and, optionally, further means.  
         [0105]     The scanning means  8  comprises a number of single scanning elements  9 , see also  FIG. 16  which are arranged directly next to one another in the longitudinal direction  14  of the device  2 . In the illustrated embodiment, the single scanning elements  9  are formed by coils  19 , see the following figures. A total of eight single scanning elements  9  are provided. Directly next to the scanning means  8 , an end plug  32  is mounted on the front end  31  of the line bore  30 .  
         [0106]     A coding pattern which is composed of a number of single patterns  7 , see also  FIG. 15 , is formed or arranged along the inner wall  22 . The scanning means  8  with its single scanning elements  9  can be assigned to a respective bit pattern group  7 .  
         [0107]     When the piston  24  is pushed to the right side in  FIG. 1 , the bit pattern  6  also moves in a corresponding way relative to the scanning means  8  to the right side in  FIG. 1 . As a result, the scanning means  8  scans the various pattern groups  7  and the relative position between scanning means  8  and coding pattern  6  can be detected through the changes of the coding pattern or the corresponding position-specific pattern groups, and the displacement path of the piston  24  to the right or left side in  FIG. 1  can be detected accordingly.  
         [0108]     As for the embodiment shown in  FIG. 1 , it should be noted that the pattern groups comprise regions of different conductivity. It should once again be noted that such a single scanning element  9  is formed by an electrical coil  19 .  
         [0109]      FIG. 2  shows the device  2  of  FIG. 1  with another transducer  1 . This essentially differs from the first embodiment in that the coding pattern  6  is formed on a pattern carrier  25  which is connected to the piston  24  by means of a stud  47 . The pattern carrier  25  extends in a direction coaxial to the inner bore  23  of the piston  24 . A scanner sleeve  26  is inserted between pattern carrier  25  and inner wall  22  of the inner bore  23 . At its free end  27 , said sleeve comprises two directly neighboring scanning means  8 ,  11 . The scanning means  8  is identical with that according to  FIG. 1 . The scanning means  21  is of a redundant type. Each of the two scanning means  8 ,  21  comprises six single scanning elements  9 . The scanner sleeve  26  is connected at its end opposite the scanning means  8 , 11 , by analogy with  FIG. 1 , to the housing end  20  as a stationary second device part  4 . Such an inverse arrangement of scanning means  8  and coding pattern  6  is also possible according to the invention.  
         [0110]     The pattern carrier  25  comprises a coding pattern  6  formed by recesses  15  and elevations  16 . This means that the various regions of the coding pattern are formed by said recesses, and each recess or elevation can comprise a single bit  13  or a number of single bits  13 .  
         [0111]     Corresponding electrical lines  29  for feeding the scanning means  8  and  11  and for determining corresponding signals in the direction of the control and evaluation unit  61  (see also  FIG. 1 ) are laid along an outer surface of the scanner sleeve  26  in the direction of the housing end  60 . At said place, the scanner sleeve  26  includes a bore  62  through which the electrical lines  29  are guided in the direction of line passage  46 .  
         [0112]      FIG. 3  shows a transducer  1 , in connection with a device  2  comprising a rotary spindle  63  as a movable first device part  3 . The rotary spindle  63  is rotatable manually, electrically, or in another way, and serves to adjust a valve, a throttle, or the like. A pattern carrier  25  is inserted into the rotary spindle  63 . This carrier, in turn, comprises regions with recesses  15  and/or elevations  16  that form a corresponding coding pattern  6 . The pattern carrier  25  is adjustable together with the rotary spindle  63  in the direction of movement  5 .  
         [0113]     A scanner carrier  28  as part of a stationary second device part  4  is inserted into the pattern carrier  25 . At its free end  31 , the scanner carrier  28  comprises a scanning means  8 . By analogy with the two preceding examples, the scanning means is formed by a number of coils  19  as single scanning elements  9  (see also  FIGS. 4 and 5 ). A line bore  30  through which a number of electrical lines  29  are guided to each of the coils  19  is arranged within the scanner carrier  28 . With its end opposite to the scanning means  9 , the scanner carrier  28  is secured to a housing  48 . A pressure-resistant multiple cable passage  40  through which the corresponding electrical lines  29  are passed is arranged within said housing.  
         [0114]     It should be noted that the scanning means  8  according to  FIG. 3  consists of twelve single scanning elements  9 . However, there is also the possibility that the twelve single scanning elements  9 , namely six elements each, form the scanning means  8  and the redundant scanning means  21  (see also  FIG. 2 ).  
         [0115]      FIGS. 4 and 5  show two further transducers  1 . These differ essentially in that in  FIG. 4  the bit pattern carrier  25  is the movable first device part or has said part assigned to it, whereas in  FIG. 5  the scanner carrier  28  is the movable first device part or has said part assigned to it.  
         [0116]     In both of them, the corresponding scanning means  8  comprises four single scanning elements  9  which are formed by light-emitting diodes. Said light-emitting diodes emit light and receive reflected light from the respective single bit of the coding pattern  6 , with different quantities of light being reflected by the various regions of the coding pattern  6  and the single bit pattern groups  7 , respectively. In such a case the different regions are formed by recesses  15  and elevations  16 . It should be noted with respect to the elevations  16  that these are only obtained relative to the recesses  15  and that in the illustrated embodiment these are not formed by elevations  16  projecting beyond an inner surface  64 . However, the elevations  16  can also be formed on the inner surface  64 , so that the recesses  15  are obtained only relative to said elevations  16  or are formed in the inner surface.  
         [0117]     An extension  11  of the single scanning elements  9  in the direction of movement  5  is essentially defined by a length  5  of a single bit  13 . Accordingly the single scanning elements  9  that are arranged side by side define a total extension  10  of the scanning means  8  in the direction of movement  5 . The extension  10  of the scanning means  8  corresponds to the length of a bit pattern group  7 , so that there is a four-bit coding of the coding pattern  6  in the embodiments of the transducer  1  as illustrated in  FIGS. 4 and 5 .  
         [0118]     Instead of the light-emitting diodes, the single scanning elements  9  according to  4  and  5  could also be formed by electrical coils  19 , see also  FIG. 16 , and a coding pattern  6  according to  FIG. 15  can be used. If supplied with a corresponding a.c. voltage, these would transmit different signals to the outside, depending on the scanning of a recess or of an elevation.  
         [0119]     As has already been explained in the preceding embodiments, regions of different conductivity, see  FIG. 15 , different reflectivity, or the like, could be formed instead of elevations and recesses. In this instance these would form the single patterns.  
         [0120]     Each of the light-emitting diodes or electrical coils  19  is connected via corresponding electrical lines  29  to a source of voltage for the supply of or signal transmission with the control and evaluation unit  61  (see also  FIG. 1 ).  
         [0121]     FIGS.  6  to  9  show further transducers  1 . In these embodiments the movable first device part  3  carries out a rotational or screw motion whereas the stationary second device part  4  extends at least in part along the circumference of the first device part  4 . Corresponding arrangements are also possible with pattern  6  and scanning means  8  according to  FIGS. 15 and 16 .  
         [0122]     Furthermore, attention should be paid in FIGS.  6  to  9  to the fact that in one half of each figure electrical coils are arranged as an example of single scanning elements  9  and that in the other half light-emitting diodes  20  are arranged as single scanning elements  9 .  
         [0123]     In  FIG. 6 , a disk  35  as a movable first device part  3 , or as a disk that is motion-connected to said device part, is provided along its circumference with recesses  15  and/or elevations  16  which form a corresponding bit pattern  6 . The length of single patterns forming the coding pattern  6  follows accordingly from the extension of the scanning means  8  in circumferential direction or along the circular path  33  of the disk  35 . In this instance, each coding pattern  6  is formed by four single bits  14 , and a respective single scanning element  9  can be assigned to each single bit.  
         [0124]     While the direction of movement  5  in  FIGS. 1-5  is straight, it is circular or helical in FIGS.  6  to  9 .  
         [0125]     In these embodiments, too, the coding pattern changes along the circumference  34  of the disk  35  and comprises corresponding position-specific single patterns in the form of bit pattern groups. What is also applicable to these embodiments is that neighboring bit pattern groups differ from one another by one single bit  13  each.  
         [0126]     While in  FIG. 6  the scanning operation is carried out with the help of the scanning means  8  radially from the outside, with the recesses and elevations  15 ,  16  being arranged in the circumference  34  of the disk  35 , the scanning operation is carried out in  FIG. 7  in a direction perpendicular to the disk plane. In this instance, the single bits  13  or bit pattern groups  7  are formed by slots in the disk surface. However, it should be noted that the regions positioned between the slots form single bits or bit pattern groups (see e.g. the bit pattern group  7  assigned to the light-emitting diodes).  
         [0127]     The slits formed in the disk extend radially to the outside. To be able to scan a single bit exactly, the single scanning elements  9  are adjustably arranged in radial direction. When smaller scanning elements  9  are e.g. used, these can be shifted radially more to the inside to be exactly assignable to a single bit  13 .  
         [0128]     In  FIG. 8 , openings are formed in the circumference  34  of the disk  35 , so that the corresponding bit patterns  6  are formed by region  17  with openings and/or regions  18  without openings. The scanning means  8  which are again formed by light-emitting diodes or electrical coils  19  are movable along the circumference  34 . The single scanning elements  9  scan the different regions  17 ,  19  and thus the single bits  13 . In accordance with the number of the single scanning elements  9 , a four-bit coding is also found in the embodiment according to  FIGS. 8 and 9 , each bit-pattern group  7  comprising four single bits  13  in this instance.  
         [0129]      FIG. 9  is a side view of the embodiment of  FIG. 8 . The regions  17  of the circumference  34  of the disk  35  that are formed by openings can especially be seen in this side view.  
         [0130]     It should additionally be noted that the disk  35  according to  FIGS. 8 and 9  comprises a disk base which is connected to a rotary shaft  50 . An annular flange which with its outside forms the circumference  34  according to  FIGS. 8 and 9  projects from said disk base. The corresponding regions  17 ,  18  are formed along the annular flange. In connection with FIGS.  6  to  9 , it should once again be noted that it is also possible that the corresponding disks are stationary and that the scanning means move around the disks  34  in circular or helical fashion.  
         [0131]      FIG. 10  depicts a four-bit coding of a corresponding coding pattern  6  in connection with an embodiment of a transducer  1 .  
         [0132]     The transducer  1  comprises the movable first device part  3 , of which essentially only the scanning means  8  is shown. The scanning means is inserted into an inner bore  23  of the stationary second device part  4 , which may e.g. be a piston according to  FIGS. 1 and 2 . However, it is possible that the scanning means  8  is movable and the coding pattern  6  is stationary.  
         [0133]     The coding pattern  6  is formed on the inner wall  22  of the inner bore  23  by regions  17 ,  18  of different conductivity. For example, the regions  17  are conductive and the regions  18  are non-conductive. The coding pattern  6  comprises a number of bit pattern groups  7  which can be scanned in successive order through the relative movement of the scanning means  8  and the coding pattern  6 . In the initial position of the scanning means  8  relative to the coding pattern  6 , as is shown in  FIG. 10 , a bit pattern group  17  is scanned that is formed of a conductive region  17 . The bit pattern group  7  comprises four single bits  13  according to the number of the single scanning elements  9  of the scanning means  8 . These single bits have a bit length  12  which is defined by a corresponding extension  11  of the single scanning elements  9 . This means that the region  17  which is scanned in  FIG. 10  as the first bit pattern group  7  comprises four single bits  13 , which form the conductive region  17  on the whole. An extension  10  of the scanning means  8  is just identical with a corresponding extension of the bit pattern group  7  or the conductive region  17 .  
         [0134]     The next bit pattern groups  7  (see the different numerical combinations in the lower part of  FIG. 10 ) are obtained from a displacement of the scanning means  8  by one single bit  13  each to the right side in  FIG. 10 . If a single bit  13  falls within a non-conductive region  18 , this is represented by a “1” whereas single bits  13  in the conductive region  17  are represented by a “0”. The coding  51  of the coding pattern  5  which defines the position-specific bit pattern groups follows from this sequence of “0” and “1”.  
         [0135]     When the four-bit coding  51  of the different bit-pattern groups  7  is each time converted into a decimal numerical value  52 , the numerical values of 0 to 15 as shown in the corresponding column are obtained. This means that a different decimal numerical value of 0 to 15 can be assigned to each of the bit pattern groups  7 . Independently of the sequence of the decimal numerical values  52 , a specific positional value  53  is assigned to each of the successively scanned bit pattern groups  7 . The positional values  53  are here in ordered form, and numerical values of 1 to 16 are assigned to them.  
         [0136]     To obtain more positional values  53 , a five-bit coding (see  FIGS. 13 and 14 ), a six-bit coding, a seven-bit coding, etc. may e.g. be used. It is known that due to the corresponding number of the bits for a coding and the two states or features for each single bit as used for a coding in the illustrated embodiment, the corresponding positional values are obtained as 2 DWB, where DWB is the data word width which includes, for instance, 4 bits, 5 bits, 6 bits, etc. The data word width is here identical with a bit pattern group or a single pattern.  
         [0137]     However, it is also possible that each single bit may have 3 different states or characteristics, so that the coding operation may be carried out in a correspondingly different way.  
         [0138]     It should here be noted in addition that when the state or feature of the single bits is e.g. conductive/non-conductive, each of said single bits may be formed by a metal ring (conductive) or plastic ring (non-conductive). When several single bits are here in the same state, the corresponding ring of metal or plastic may be given a larger width.  
         [0139]      FIG. 11  shows the measured signal information  37  in connection with an electrical coil  9  as the single scanning element  9  and conductive/nonconductive regions  17 ,  18  as the coding pattern  6 . This information is obtained when the bit pattern  6  is scanned by the corresponding scanning means  8  or by a single scanning element  9 . The path  9  is plotted on the abscissa and an analog resolution  54  of a signal voltage  58  for an electrical coil  19  is shown on the ordinate. This means that the curve of the measured signal information  37  is evaluated in an analog or quasi analog form in the region of the signal voltage  58 . This yields a very exact curve or profile of the measured signal information  37  in dependence upon the path  59 .  
         [0140]     Upon a first scanning of the bit pattern  6 , measured signal information  37  can e.g. be stored in the storage means  36  of the control and evaluation means  61  of the transducer  1 . When measured signal information is subsequently obtained during current scanning, this information can be compared with the measured signal information stored. When the two types of measured signal information are then compared, the relative position of the movable first device part and stationary second device part can be detected via the bit length  12  of a single bit  13  with a higher resolution. For instance, the types of measured signal information from one, two, three, four or more single scanning elements  9  are compared with one another and made congruent, so that it is not only possible to determine the position accurately at the bit level, but it is also possible to sense transitions between bits, sections between the bits, etc. The corresponding resolution of the position follows substantially from the analog bit resolution  54  according to  FIG. 11  and a corresponding bit width  12 , see e.g.  FIG. 10 .  
         [0141]     Since the measured-value signal information  37  is recorded during a first scanning operation and since corresponding current measured-value information is recorded, it is possible in addition—if these types of information are stored in a non-volatile storage means—that these types of information are retrieved and compared with one another in case of failure of the electrical means at a later time upon a renewed start and that the relative position between the first and second device part is determined in an exact and direct way. This is also possible with the coding patterns as such, and in this instance it might be that only upon a renewed start the specific bit pattern group next to the position has to be scanned if there is no exact assignment of scanning means and bit pattern group.  
         [0142]      FIG. 12  shows a simple transducer  1  for explaining a few measurement parameters. The transducer  1  comprises a movable device part and a stationary device part, one of said device parts being e.g. the scanner carrier  28  and the other device part the bit pattern carrier  25 . Electrical coils  19  (not shown) are arranged side by side on the scanner carrier  28  as single scanning elements  9 , the number of the single scanning elements  9  defining the overall length of the scanning means  8  and also the length of the bit pattern group.  
         [0143]     A so-called mechanical bit width  56  can be assigned to each single scanning element  9 . The total data word width  55  or extension  10  of the scanning means  8  follows from the number of the single scanning elements.  
         [0144]     In this instance, the resolution follows as the quotient of an analog bit resolution, see reference numeral  54  in  FIG. 11 , and the mechanical bit width  56 . The analog bit resolution is e.g. indicated in step per bit and the mechanical bit width in mm per bit.  
         [0145]     The length to be measured by the transducer  1  follows from the product of mechanical bit width  56  and the maximum number of the possible positions  54  reduced by one (see  FIG. 10 ).  
         [0146]     The total length of a path to be scanned by the scanning means follows essentially from the addition of the length of the measurement path and the extension  10  of the scanning means  8 .  
         [0147]     The maximum length of a region  17  (see the right half in  FIG. 12 ) follows also from said extension  10  or sensor length  57  of the scanning means  8 .  
         [0148]      FIGS. 13 and 14  show a further coding pattern  6  with corresponding individual patterns in the form of bit pattern groups. In this instance,  25  decimal values  52  or  32  positional values  53  can be assigned to the coding pattern. Each single pattern group  7  comprises five single bits  13  as the single pattern in this connection.  
         [0149]     The different single patterns, in turn, follow from the displacement by one respective single bit  13  along the serial arrangement of the coding pattern  6  according to  FIG. 14 . In this context it should be noted that the bit pattern groups assigned to the respective ends of the coding pattern  6  are obtained by cyclic displacement. This means that e.g. the fourth single pattern group “1110” from last according to  FIG. 13  follows from the last four “1” values at the right side in  FIG. 14  and from the first “0” at the left side in  FIG. 14 . The three single pattern groups following said fourth single pattern group from last according to  FIG. 13  are obtained by analogy.  
         [0150]      FIG. 15  is a top view on an embodiment of a pattern carrier  25  according to the invention which has arranged thereon a coding pattern  6  in the form of position-specifically differently structured single patterns  7 : Said single patterns  7  are formed by conductivity patterns  49  that are arranged one after the other in the direction of movement  6 . Said pattern carriers  25  can be connected to one of the device parts according to the preceding figures, with a corresponding scanner carrier  28  being illustrated in the subsequent  FIG. 16 . Pattern carrier  25  and scanner carrier  28  according to  FIGS. 15 and 16  are displaced relative to one another.  
         [0151]     The conductivity patterns according to  FIG. 15  are approximately diamond-shaped, the patterns comprising edges  65  rising in the direction of movement  5  and edges  66  falling in the direction of movement. The conductivity patterns  49  are made symmetrical relative to a horizontal plane  69  extending in the direction of movement  5 , and a symmetrical configuration may also be present with respect to a vertical plane  17  perpendicular to the direction of movement  5 .  
         [0152]     The different conductivity patterns  49  are e.g. formed by a conductive metallic material, such as copper or the like. This can be structured by etching, as is e.g. known from the technical field of printed circuit boards.  
         [0153]      FIG. 16  shows a further embodiment of a scanner carrier  28 . Said carrier has arranged thereon six conductors  77  to  81  that are connected to corresponding coils  71  to  76 . Further conductors of the same type are arranged on the back side (not shown) of the scanner carrier  28  and are each connected approximately in the middle to the corresponding coils  71  to  76 .  
         [0154]     The various coils  71  to  76  form corresponding single scanning elements  9  of the scanning means  8 .  
         [0155]      FIG. 17  shows a detail “X” of  FIG. 16  on an enlarged scale. Said detail is particularly the coil  71  as the single scanning element  9 , which is essentially square and comprises a winding which is winding inwards in the form of a spiral. The winding end is passed to the corresponding other side of the scanner carrier  28  according to  FIG. 16  and is there connected to a further conductor.  
         [0156]     The construction of the further coils  72  to  76  is analogous.  
         [0157]      FIG. 18  shows a corresponding transducer  1  which is formed by two scanner carriers  28  according to  FIG. 16  and a pattern carrier  25  according to  FIG. 15 . The pattern carrier  25  is arranged between the two scanner carriers  28  arranged relative to each other and is supported in a displaceable way relative thereto. Corresponding coils  71  to  76  are arranged on both scanner carriers  28  with corresponding conductors  77  to  82  according to  FIG. 16 , said members being not shown in  FIG. 18  for the sake of simplicity. Corresponding coils  71  to  76  are illustrated only for the lower scanner carrier  28  in  FIG. 18 .  
         [0158]      FIG. 19  is a basic sketch for showing the assignment of coils  71  to  76  to the conductivity patterns  49 , as is obtained for a transducer  1  according to  FIG. 18 .  
         [0159]     During the relative movement of the corresponding coils  71  to  76  towards the conductivity patterns  49 , signals according to  FIG. 21  are obtained (see the upper six signal curves). The corresponding signal curves of each coil are phase-shifted approximately by the width of a coil. According to the invention attention must be paid that the extension  87  of all coils  71  to  76  in the direction of movement  5 , see  FIG. 15 , is greater than a maximum length  88  of a rising or falling edge  65 ,  66  of the conductivity pattern  49 , see  FIG. 19 . It is thereby ensured that at least one of the coils senses either the next following conductivity pattern or the respectively other edge  65 ,  66  of the one conductivity pattern  49  that is just being scanned. This means that at least one transition from rising to falling edge  65 ,  66  should be sensed on a conductivity pattern  49  or between two conductivity patterns  49 . Attention must here be paid that the corresponding edge rises  67 ,  68  from rising edge or falling edge  66  relative to the horizontal plane  69  or the direction of movement  5  are different in their absolute value. This means that the rise  67  differs from the rise  68  in its absolute value, the absolute values of the rises  65 ,  68  being also different from the absolute values of the edges of the next neighboring conductivity pattern  49 . At the same height  89  of each conductivity pattern  49  vertical to the horizontal plane  69 , it is thereby ensured that particularly the transitions between the conductivity patterns  49  and the transitions between rising and falling edge  65 ,  66  are definitely obtained through the corresponding signals of the coils  71  to  76  (see the upper six curves in  FIG. 21 ).  
         [0160]     In  FIG. 21 , and particularly in the upper six illustrated signal curves or profiles, attention must be paid that the curves correspond to the scanning of the whole coding region of the pattern carrier  25  according to  FIG. 15 , each of the curves being assigned to one of the coils  71  to  76 . When the corresponding scanner carrier  28  is then positioned in a specific relative position with respect to the pattern carrier  35 , the signals of the six coils  71  to  76  each yield a signal serving to determine the position in an exact way in that the corresponding signals and their relations to one another are compared with the curves according to  FIG. 21 .  
         [0161]     In the lower part of  FIG. 21 , the noise ratio from an actual position to another position is illustrated in relation to the upper six curves.  
         [0162]      FIG. 20  is a top view on a further embodiment of a scanner carrier  28  which basically corresponds to the two scanner carriers  28 ,  83  according to  FIG. 18 . In  FIG. 20 , the scanner carrier  28  is formed from a foil material on which the conductors  77  to  82  and the scanning coils  71  to  76  are arranged accordingly. These may be formed either by etching a copper coating of the corresponding foil, as is known in a similar way for printed circuit boards, or the like.  
         [0163]     The scanner carrier  28  according to  FIG. 20  is constituted of an approximately circular central piece  84  that serves the connection of a corresponding electrical connection means, with two carrier arms  85 ,  86  projecting laterally from the central piece  84  opposite each other. Along the carrier arm  86  the coils  71  to  76  are powered in parallel at the end of the carrier arm  86 . On the back side of the carrier arm  86  a connection is established via corresponding further conductors to the coils  71  to  76  arranged at the end of the carrier arm  85  and then a connection via further conductors  77  to  82  back to the central piece  84 . At said place single coils  71  to  76  can then be queried individually via corresponding contacts.  
         [0164]     Upon use of the scanner carrier  28  in  FIG. 20  the two carrier arms  85 ,  8 , are bent onto and arranged in parallel with each other, a corresponding pattern carrier  25  being arranged between the two, e.g. according to  FIG. 15 , to be displaceable relative thereto.  
         [0165]     It should additionally be noted that the geometrical structuring of the corresponding conductivity patterns  49  according to  FIG. 15  and  9 , respectively, is only by way of example; other geometrical structures are possible that permit position-specific signals by corresponding single scanning elements  9 . For example, differently curved conductivity patterns are possible that also ensure that different signals are produced by the corresponding single scanning elements during displacement along the coding pattern. Also the different arrangement of scanning elements  9  and patterns  6  according to  FIG. 1-9  are possible with the embodiments of  FIG. 15-20 .