DE4311267A1 - Position sensor - Google Patents

Abstract

A position sensor for monitoring the radial angle position and/or the angular velocity and/or the direction of rotation of a driven shaft is described which exhibits a rotor which is connected to the shaft and is laterally magnetised in a number of poles on the circumference and which interacts with magnetic field sensors which are arranged on a board extending perpendicularly to the axis of the shaft and the output signals of which are evaluated in corresponding evaluating circuits.

Description

The invention relates to a position transmitter for monitoring the radial angular position and / or the angular velocity and / or the direction of rotation of one in particular Electric motor driven shaft.

Position sensors come with the monitoring and automate control of motion generated by electric motors operations. Such position transmitters often operated continuously, with quick changes the shaft speed and reversing the direction of rotation of the Wave can occur, which is a not inconsiderable mechanical stress of such position sensors contribute.

Furthermore, when reversing the direction of rotation of the Motors an axial displacement of the shaft occur that too Malfunctions in measuring operation and in unfavorable cases also for Can cause damage to the position encoder.

The object of the invention is to provide a position sensor gangs mentioned to create the compact and robust formed and in a simple manner with different elec tromotor designs can be coupled, a high closing in operation has reliability and is particularly insensitive against axial play of the motor shaft.

To solve this problem, the features of the label the part of claim 1 provided.

By the number of magne provided on the circumference of the runner The north and south poles can resolve the position angle measurement of the position encoder can be set, where by appropriate choice of the number of north and south poles a resolution of the radial angular position of the motor shaft in Range of 3 ° can be reached without problems. If one of the like measuring accuracy is not required, so it is also possible  Lich, the runner, if necessary, only with a north and a south pole equip.

To determine the direction of rotation of the shaft, two magnetic field sensors two out of phase with each other Output signals A and B generated. The size of the phase ver shift of the output signals A and B results here from the number of magnetic provided on the rotor North and South Poles and from the radial angle at which the two magnetic field sensors are aligned with each other. If the direction of rotation of the shaft changes the phase shift between the output signals A and B. their sign and therefore enables one at any time Determination of the direction of rotation of the shaft.

Necessary prerequisite for a determination of the rotary device of the wave is the occurrence of a phase shift between the output signals A and B, but not the Size of this phase shift. Therefore, a variety of structural embodiments with regard to the number of magnetic poles of the rotor and radial angular position of the two magnetic fields possible sensors, all of which lead to a phase shift of the Output signals A and B lead and therefore a direction of rotation allow determination.

It is also essential for the invention that the measured value detection by the Hall sensors takes place without contact. By avoiding any mechanical measuring components, for example, sliding contacts or the like, omitted other maintenance and replacement work Wear parts. This will increase the reliability of the measurement arrangement increased and their suitability for continuous operation ver improves.  

Because the magnetic fields that detect the magnetic field of the rotor sensors at a distance, d. H. non-contact around the rotating Arranged rotor and the magnetic poles in the axial direction chend dimensioned, it is also achieved that a ge do not know any axial play of the motor shaft Has an influence on the measuring behavior of the position encoder. There is also the functional reliability of the position beneficially influenced.

According to a preferred embodiment, the runner is made made of a ferrite with molded plastic flange, whereby this an internal serration and the shaft accordingly has an external serration. The ferrite is on Multi-pole circumference laterally magnetized.

Furthermore, due to the simple, lie in one level de Arrangement of the rotor and that on a removable board attached magnetic field sensors an easy access speed of the measuring arrangement if assembly or maintenance work.

A conventional pulse counter can be directly on the positions encoder are connected, the position encoder generated binary direction of rotation signal the counting direction of the count lers determined and the count signal the counter accordingly in incremented or decremented.

According to an advantageous embodiment, the runner an odd number of magnetic north and south poles point and the magnetic field sensors can at an angle 90 ° to each other. Under that advance there is a phase shift of the output signals A and B of 90 °.  

A particularly compact arrangement results when the bottom sition transmitter in a connected to the motor housing Additional housing is housed, the additional housing as an extension of the motor housing with essentially egg ner cross-sectional shape corresponding to the motor housing forms can be.

With a particularly advantageous in terms of construction Embodiment is the arrangement of the position sensor a motor shield penetrated by a motor shaft, whereby to position the magnetic field sensors on the rotor dial outside concentrically surrounding carrier ring provided is that with both the circuit board and the motor plate is firmly connected.

A preferred embodiment of the position sensor housing be is that together with the engine end shield the same a corresponding housing wall section is also cast, so that only one end cover as an additional com component is added. This end cover may have a hole for have the shaft bushing to z. B. a Montagemög possibility for a fan, an external brake and the like to create chen.

The preferably round or circular circuit board has recesses that allow fastening screw ben, e.g. B. for the end cover, past the board in the Screw the end shield. This way, elaborate Screw receptacles in the housing wall can be avoided.

Basically can be used to generate the applied to the meter Count signal either one of the output signals A or B ver be applied. However, the count signal is preferred gebil from the output signal A and the output signal B. det, for example, each in the output signal A or in  Output signal B occurring pulse at least one count pulse generated in the count signal.

A particularly advantageous embodiment is given if each rising and / or falling pulse edge of one Pulses in the output signal A and / or B in the evaluation scarf device generates a count pulse in the count signal.

To ensure with certainty that each counting pulse of the Count signal in the counter according to the current direction of rotation direction of the shaft is registered in the correct counting direction, it is preferably provided that the applied to the meter Direction of rotation signal every time a pulse occurs in egg nem of the output signals A and B from a comparison of the Pha position of the current pulse compared to the previous pulse is determined, in particular that which can be fed to the counter Electronic counter signal compared to the direction of rotation signal is delayed to ensure that when entering a defined one of each count pulse on the counter Signal state of the direction of rotation signal on the counter is present.

A functional check of the position can expediently be carried out take place via a malfunction signal that the Occurrence of at least two successive pulses in one and the same output signal A or B from the evaluation circuit is generated. A failure of one of the magnetic fields sensors will therefore subsequently cause the radio to respond tion fault signal.

The signal processing carried out by the evaluation circuit tion is preferably carried out directly on the magnetic fields soren carrying board.

To display one of the output signals A or B and / or the Direction of rotation and / or the malfunction signal can  each light-emitting diodes may be provided on the board with also during a final inspection, a first installation drive or maintenance work a quick and pro easy checking of the functionality of the position is possible.

Expediently, one is on the housing as the electrical output attached, multi-pole, electrically ver with the board tied plug socket provided, the at least connections for the count signal and the direction of rotation signal, and in addition, optional connections of the output signals A and / or B, the malfunction signal, an analog Speed output signal, connections for the supply chip position encoder and a voltage-stabilized Has voltage output that for the voltage supply of a Provided directly on the socket attachable measuring device is.

The invention is described below, for example, with the aid of Drawing described; in this shows:

Figure 1 is a longitudinal sectional view of a position sensor located in an additional housing on a Mo torgehäuse.

Fig. 2 is a longitudinal sectional view of the position transmitter from Fig. 1;

FIG. 3 shows a side view of the rotor runner from FIG. 2; FIG.

Fig. 4 is a plan view of the position sensor from point X seen at abgenom men lid of the additional housing;

Fig. 5 is a functional diagram of the evaluation circuit of the position transmitter; and

Fig. 6 shows the output signals A and B and the direction of rotation signal and a counting pulse when the direction of rotation of the shaft is reversed.

In Fig. 1, a unit consisting of a motor 10 and a position sensor 12 is shown, which has a motor housing 16 , which is closed at the end by a motor shield 14 , and an additional housing 18 connected to the motor shield 14 with an end cover 20 attached at the end. A motor shaft 24 provided with a concentric motor armature 22 runs centrally in the motor housing 16 and is surrounded in the region of the motor armature 22 by a coaxially arranged excitation winding 26 fixed to the housing. The motor shield 14 has a central bore 28 through which the motor shaft 24 is passed into the additional housing 18 , and in the inner circumferential area a bearing 30 is provided for mounting the motor shaft 24 . The opposite, shown in the lin ken part of FIG. 1, the end of the motor shaft 24 is used to transmit power to a mechanical device, not shown, such as a transmission.

Within the additional housing 18 , the motor shaft is rotatably coupled to a cylindrical rotor 32 which is provided on the circumferential surface with an alternating number of magnetic north and south poles in the circumferential direction. The rotor 32 is radially outside contact-free surrounded by a concentric support ring 34 which is received in a guide groove 36 of the motor shield 14 in a snug fit connection and which on its end opposite the motor shield 14 via a screw connection 38 with a substantially perpendicular to the motor shaft 24 Board 40 is connected.

The board 40 has in its central region a passage opening 42 which is traversed by the end portion of the motor shaft 24 . Further, the circuit board is mounted 40 on their electrical leads 44 to an opening provided on the auxiliary housing 18 receptacle 57th

Fig. 2 shows an enlarged view of the position sensor according to the invention from Fig. 1. From this illustration it can be seen that the carrier ring 34 is provided on its inner circumference with an axial groove 46 lying in the plane of the drawing, in which a magnetic field sensor, generally a Hall Element, a small distance radially above the magnetized th peripheral surface of the rotor 32 is received. The Hall sensor is electrically conductively connected to the circuit board 40 via its lead wires 50 .

A second Hall sensor is accommodated in the same way in a two-th axial groove provided in the carrier ring 34 , which is inclined at an angle of 90 ° with respect to the first axial groove 46 and is therefore not visible in FIG. 2.

FIG. 3 shows a schematic side view of the rotor 32 and clearly shows the alternating sequence of magnetic north and south poles on the peripheral surface of the rotor 32 in the circumferential direction.

In Fig. 4, the circuit board 40 is shown within the additional housing 18 , seen in the direction of arrow X in Fig. 1 with the end cover 20 removed. The additional housing 18 has an essentially square outline and is provided in the region of the corners with screw holes 52 , via which the end cover 20 and the additional housing 18 are connected to the motor housing 16 by means of screws. The additional housing 18 has cooling ribs 54 on its lateral outer surfaces and is centrally provided with a plug socket 57 on the ceiling surface 56 . The circuit board 40 is suspended from the leads 44 of the plug socket 57 protruding into the additional housing 18 .

As indicated in Fig. 4, the circuit board 40 is on its side facing away from the motor shield 14 with a number of electronic components 58 , which belong to an evaluation circuit 59 which will be explained in more detail below. Furthermore, the circuit board 40 has light-emitting diodes 60 , 60 'and 60 ''in electrical connection with the evaluation circuit.

The course of the carrier ring 34 on the side of the circuit board 40 facing the motor shield 14 is shown in dashed lines for better understanding of the illustration in FIG. 4. Be the mounting of the board 40 on the support ring 34 via the three screw connections 38th

Fig. 5 shows a schematic representation of the switching device of the electronic evaluation circuit 59 and the socket 57 . The output signals A and B from the two Hall sensors 48 are present both at the two inputs 70 , 71 of the evaluation circuit 59 and also directly at the output connections 80 , 81 of the plug socket 57 . The voltage supply to the evaluation circuit 59 takes place via the input voltage connection 82 of the socket 57 and is between 7 and 24 volts DC. In addition to a stabilized DC voltage output 83 , the evaluation circuit 59 has an output of the count signal 84 , the direction of rotation signal 85 , a functional interference signal 86 and an analog speed output 87 .

When the motor shaft 24 rotates, a magnetic field with a temporally alternating polarity occurs at the two Hall sensors 48 . The magnetic field generates in the output signal lines A and B of the Hall sensors 48 a sequence of electrical pulses which, due to the 90 ° angular position difference of the Hall sensors 48 and due to the uneven number of magnetic north or Southern Poland have a phase shift of 90 ° to each other.

The evaluation circuit 59 detects the signal pulses from the Hall sensors 48 arriving via the inputs 70 , 71 both on the basis of the rising and falling pulse edges and provides a counting signal at the output 84 , which for each signal pulse running - regardless of whether at the input 70 or 71 - has two temporally defined counting pulses, one for the rising pulse edge and one for the falling pulse edge.

The height and pulse duration of the count pulse is determined by the configuration of the evaluation circuit 59 and is generally defined in such a way that reliable detection of the count pulses is ensured with conventional counters. For example, the generated counting pulses can have a rectangular shape and have pulse heights in the volt range with pulse lengths in the range of a few microseconds.

Furthermore, the evaluation circuit 59 determines the current direction of rotation of the motor shaft 24 on the basis of the phase position of the rising and falling pulse edges of the last two signal pulses arriving at the inputs 70 and 71 and outputs a direction signal 85 indicating the current direction of rotation of the shaft 24 . The direction of rotation signal 85 has two signal states corresponding to the two possible directions of rotation of the motor shaft 24 .

In measuring mode, the counting signal output 84 and the direction of rotation signal output 85 of the evaluation circuit 59 are connected to an external, not shown counter which, when a counting pulse occurs, depending on the value of the applied rotational direction signal 85, performs an incrementation or decrementing of the counter reading by 1. In order to ensure that the current direction of rotation signal 85 corresponding to the rotation generated by this counting pulse is already present at the counter at the time of the arrival of a counting pulse, the counting signal 84 in the evaluation circuit 59 is compared to the direction of rotation signal 85 by a small time span, for example 10 µsec, delayed. This also ensures that the direction of rotation signal 85 always has a defi ned state when a counting pulse occurs at the counting signal output 84 , so that the counter can always clearly register the counting pulse either as a decrementing pulse or as an incrementing pulse.

To further illustrate the operation of the evaluation circuit 59 are the output signals A and B occurring in a rotation direction sel sel of the motor shaft 24 in Fig. 6, the direction of rotation signal 58 determined by the evaluation circuit 59 and a counting pulse 84 'of the counting signal also generated by the evaluation circuit 59 84 shown over a time axis.

In the left part of FIG. 6 two signal pulses appearing in the output signals A and B are shown, which are phase-shifted by 90 ° and are shown with different amplitudes for better differentiation. In the present exemplary embodiment, it follows from the fact that the signal pulse in the output signal B occurs before the signal pulse in the output signal A that there is a direction of rotation of the motor shaft 24 in the counterclockwise direction. A voltage-free signal state of the direction of rotation signal 85 is assigned to this direction of rotation.

If the direction of rotation of the motor shaft 24 is reversed, a single, long signal pulse B can occur, as is shown in the middle area of FIG. 6. Since the falling pulse edge at the signal output B occurs before the occurrence of a rising pulse edge at the signal output A, ie the alternating sequence of rising and falling pulse edges characteristic of a stationary rotary movement is broken in the two output signals A and B, occurs when the drop the pulse edge in the output signal from B, the change in the signal state at the direction of rotation signal 85 '. At the same time, when the falling pulse edge occurs in the evaluation circuit 59, a count signal pulse 84 'is generated, which, as indicated in FIG. 6, is, however, outputted for a certain period of time for the reasons already mentioned. Here, in FIG. 6, both the time delay and the pulse duration of the counting pulse 84 'are reproduced in a greatly enlarged manner in comparison with the time scale plotted on the time axis.

Furthermore, a malfunction signal is provided at the output 86 of the evaluation circuit 59 , which outputs a signal value indicating a malfunction of the measuring system whenever a signal pulse from one and the same output signal A or B occurs twice in succession. There, the malfunction signal 86 switches in the event of a failure of one of the Hall sensors to malfunction.

A brief response of the malfunction signal, which, however, does not indicate a malfunction and which can also be suppressed electronically, can result when the motor direction of rotation is reversed, since two successive signal pulses can also occur in the same output signal A or B - however, as shown in Fig. 6 shows do not have to.

Furthermore, an analog speed output 87 is provided on the evaluation circuit 59 as a current output, which can be used, for example, to operate an external, analog speed display instrument. Furthermore, can be operated with the digital counter via the sta bilized voltage output 83 of the socket 57, a plug-in directly onto the socket 57 measuring or indicating instrument.

For direct control of the functionality of the position encoder, the three LEDs 60 , 60 'and 60 ''are provided, each of which is connected to one of the signal outputs A or B, the direction of rotation signal 85 and the malfunction signal 86 . With the cover 20 of the additional housing 18 removed, a function check of the position transmitter is thus possible on the basis of the light-emitting diodes 60 , 60 'and 60 '', without the need for an external test device which can be connected to the signal socket. This can be particularly advantageous if, due to interfering control signals, proper operation of the position sensor is endangered. If this is the case, the circuit board 40 can be provided with a copper layer which contributes to improved shielding against electromagnetic interference.

Reference list

10 engine
12 position sensors
14 motor plate
16 motor housing
18 additional housing
20 end caps
22 motor anchors
24 motor shaft
26 excitation winding
28 central bore
30 bearings
32 runners
34 carrier ring
36 guide groove
38 screw connection
40 board
42 passage opening
44 supply line
46 axial groove
48 Hall sensor
50 lead wires
52 screw hole
54 cooling fins
56 Top of the additional housing
57 plug socket
58 electronic components
59 Evaluation circuit
60 light emitting diodes
60 ′ light emitting diodes
60 '' LEDs
70 Input A of the evaluation circuit
71 Input B of the evaluation circuit
80 Output A of the plug socket
81 Output B of the socket
82 Input voltage connection
83 stabilized voltage output
84 count signal output
84 ′ count signal pulse
85 Direction of rotation signal output
85 ′ direction of rotation signal
86 Malfunction signal output
87 analog speed output
A output signal of the first Hall sensor 48
B output signal of the second Hall sensor 48 .

Claims (32)

1. position transmitter for monitoring the radial angular position and / or the angular velocity and / or the direction of rotation of a shaft driven in particular by an electric motor,
characterized,
that the shaft ( 24 ) is connected in a rotationally fixed manner to a cylindrical rotor ( 32 ) which is concentric with the shaft ( 24 ) and has a predetermined number of alternately arranged magnetic north and south poles over the circumference,
that at a distance radially outside the circumference of the rotor ( 32 ) two at a predetermined radial angle against each other staggered electronic magnetic field sensors ( 48 ), in particular Hall sensors ( 48 ) are provided, which locally scan the magnetic field in the region of the peripheral surface of the rotor ( 32 ) and each deliver a magnetic field-dependent output signal A or B,
that when the shaft ( 24 ) rotates, the output signals A and B each form a chronological sequence of phase-shifted pulses, and
that an the output signals A and B evaluating electronic evaluation circuit ( 59 ) is provided which has a generated from at least one of the output signals A or B tes, counting pulses ( 84 ') having a counting signal ( 84 ) and one from the phase relationship of the pulses of the output signals A. and B certain, the direction of rotation of the shaft ( 24 ) indicating binary direction signal ( 85 ) is generated. 2. Position sensor according to claim 1 with a with the count signal ( 84 ) and the direction of rotation signal ( 85 ) feedable counter, characterized in that the counter when a count pulse ( 84 ') occurs in the count signal ( 84 ), the count as a function of the signal state of the direction of rotation signal ( 85 ) either incremented by 1 or decremented. 3. Position sensor according to claim 1 or 2, characterized in that the rotor ( 32 ) has an odd number of magnetic rule's north and south poles and consists of a multi-pole laterally magnetized on the circumference ferrite. 4. Position transmitter according to one of the preceding claims, characterized in that the magnetic field sensors ( 48 ) are offset from one another at a radial angle of 90 °. 5. Position transmitter according to one of the preceding claims, characterized in that in the region of the rotor ( 32 ) a perpendicular to the shaft axis ( 24 ) extending board ( 40 ) is provided, in which the magnetic field sensors preferably working in latch operation tend existing ( 48 ) facing the end shield are soldered to the corresponding soldering points on the board. 6. Position transmitter according to claim 5, characterized in that the circuit board ( 40 ) has a passage opening ( 42 ) penetrated by the shaft ( 24 ). 7. Position sensor according to one of claims 5 or 6, characterized in that the circuit board ( 40 ) is housed in an additional housing ( 18 ) connected to the motor housing ( 16 ), the additional housing preferably being cast onto the motor bearing shield and an end cover for closure of the additional housing is provided, which may have an opening for the shaft bushing. 8. Position sensor according to claim 7, characterized in that the cross-sectional shape of the additional housing ( 18 ) corresponds substantially to that of the motor housing ( 16 ). 9. Position sensor according to claim 7 or 8, characterized in that the circuit board ( 40 ) is connected to a tongue of variable length combined connections with a multipole connector socket ( 57 ) provided on the additional housing ( 18 ). 10. Position sensor according to one of the preceding claims, characterized in that the rotor ( 32 ) is surrounded radially outside without contact by a concentric carrier ring ( 34 ), the guide elements ( 46 ) for positioning the on the circuit board ( 40 ) attached magnetic field sensors ( 48 ) having. 11. Position sensor according to claim 10, characterized in that the board ( 40 ) with the support ring ( 34 ) verbun the, in particular is screwed. 12. Position transmitter according to claim 10 or 11, characterized in that the carrier ring ( 34 ) on the side of the board ( 40 ) abge facing in a centering fit ( 36 ) of a motor shaft ( 24 ) penetrated motor shield ( 14 ) is fixed. 13. Position sensor according to one of the preceding claims, characterized in that the magnetic field sensors ( 48 ) and / or the magnetized te rotor ( 32 ) are dimensioned sufficiently large in the axial direction in order to ensure that the measuring capability of the system also occurs within a definable axial play To ensure axial displacement of the shaft ( 24 ). 14. Position transmitter according to one of the preceding claims, characterized, that the pulses of the output signals A and B essentially chen rectangular shape. 15. Position transmitter according to one of the preceding claims, characterized in that the evaluation circuit ( 59 ) generates the count signal ( 84 ) as well from the output signal A as from the output signal B. 16. Position transmitter according to one of the preceding claims, characterized in that in the evaluation circuit ( 59 ) each rising and / or falling pulse edge of a pulse in the output signal A and / or B generates a count pulse ( 84 ') in the count signal ( 84 ). 17. Position transmitter according to one of the preceding claims, characterized in that in the evaluation circuit ( 59 ) the direction of rotation signal ( 85 ) each time a pulse occurs either in the output signal A or B from a comparison of the phase position of the current pulse to the previous one of the output signals A or B occurring pulse is redetermined. 18. Position sensor according to claim 15 to 17, characterized in that the evaluation circuit ( 59 ) outputs the count signal ( 84 ) against the direction of rotation signal ( 85 ) electronically delayed. 19. Position transmitter according to claim 18, characterized in that the time delay of the count signal ( 84 ) relative to the direction of rotation signal ( 85 ) is between 1 and 100 µsec. 20. Position transmitter according to one of the preceding claims, characterized in that the evaluation circuit ( 59 ) generates a malfunction signal ( 86 ) when at least two successive pulses occur in one and the same output signal A or B. 21. Position sensor according to claim 5 to 20, characterized in that the evaluation circuit ( 59 ) on the magnetic field sensors ( 48 ) holding board ( 40 ) is provided. 22. Position transmitter according to claim 21, characterized in that the circuit board ( 40 ) with light-emitting diodes ( 60 , 60 ', 60 '') is provided, the pulses of at least one of the output signals A or B and / or the state of the direction of rotation signal ( 85 ) and / or the status of the malfunction signal ( 86 ). 23. Position sensor according to one of the preceding claims, characterized in that a provided on the housing multi-pole, electrically connected to the evaluation circuit connec den socket ( 57 ) is provided as the electrical output, the at least connections to the count signal ( 84 ) and the direction of rotation signal ( 85 ). 24. Position transmitter according to claim 23, characterized in that the plug socket ( 57 ) further connections of the output signals A and / or B, and / or the functional fault signal ( 86 ) and / or an analog speed output ( 87 ) and / or connections for the supply voltage ( 82 ) of the position transmitter and / or a voltage-stabilized voltage output ( 83 ), which is used to supply voltage to a directly attachable to the socket, provided with a meter. 25. Position transmitter according to claim 23 and 24, characterized in that the signal outputs of the plug socket ( 57 ) are either out as TTL outputs or as open collector outputs. 26. Position transmitter according to one of the preceding claims, characterized, that determine the function of the position transmitter Components on several essentially the same outline Chen boards are arranged, and that these boards via an additional, the plate system vertically through setting plug-socket system with the same signal inputs and outputs connected or coupled to them are. 27. Position transmitter according to claim 26, characterized, that the board system has a board that without Equipping the bus system and without the other boards is fully functional. 28. Position sensor according to one of the preceding claims, characterized in that one of the optionally several boards via a combined to a cut-to-length tongue is connected to a connector on the additional housing ( 18 ) provided multi-pin socket ( 57 ). 29. Position transmitter according to claim 2 and one or more of further claims, characterized, that the counter is on one of the additional boards is arranged and the connector used is sufficient Number of connections to the position signal output as a parallel and digitally coded signal can. 30. Position transmitter according to one of the preceding claims, characterized, that one provided with suitable relay units  Speed monitoring circuit on one of the too Additional boards is arranged and depending on the pro the relay outputs depending on the Speed state switches. 31. Position transmitter according to one of the preceding claims, characterized, that in addition to the magnetic field sensors, an infrared Photoelectric switch is provided on the motherboard preferably an additional one on the magnetized Läu fer attached reflection mark as an index signal gropes. 32. Position transmitter according to one of the preceding claims, characterized, that the sensor inputs and the sensor outputs of the IR Photoelectric switch preferably at the same height as that Magnetic field sensors are arranged so that the required Reflection area basically on the magnetized Runner is attachable.