Patent Description:
For various reasons, it is crucial to know in elevators the speed and/or the position of an elevator car and/or a counterweight of the elevator. The position of an elevator car in a shaft can be determined for example by means of a linear encoder. A problem related to the use of linear encoders is that a linear encoder requires a scale which must extend over the whole length of the shaft, which makes the linear encoders awkward and vulnerable. For example, dirt can affect the reliability of linear encoders. Another solution for determining the speed and/or position of an elevator car is an encoder having a friction wheel that is engaged with a guide rail of the elevator car. A problem of this solution is possible wheel slippage, which makes such encoders unreliable. Also in escalators, moving walkways and moving ramps there is a need for a reliable and cost efficient way of determining the speed and/or position of different components.

<CIT> discloses a sensor for sensing movement of a moveable member along a movement path. The sensor comprises a transducer connected in a loop circuit and a detection circuit for detecting variation in the frequency of the loop circuit caused by variation in the relative positioning of the member and the transducer.

<CIT> discloses a rotary position detector. A sensor detects a distance to a body to be detected from the change of impedance of a highfrequency coil.

<CIT> discloses a rotary encoder comprising a sensor element with a transducer element and exciter system.

<CIT> discloses a linear inductive position sensor for an angle measurement of a rotating component.

An object of the present invention is to provide an improved measurement arrangement for measuring the rotation speed of a component of an elevator. The characterizing features of the arrangement according to the invention are given in claim <NUM>. Another object of the invention is to provide an improved method of monitoring the rotation speed of a component of an elevator. The characterizing features of the method according to the invention are given in the other independent claim.

With the measuring arrangement and the method according to the invention, the rotation speed of a rotating component in an elevator can be determined reliably in an inexpensive way. The measuring arrangement is not sensitive to dirt and mechanical contact between the rotating part and the sensor is not needed. Based on the speed measurement, also the position of an elevator car, counterweight or the like can be determined.

According to the invention, the component or the measurement part is provided with a surface that is shaped and/or positioned so that the distance from the surface to the inductive sensor changes as the component rotates about the rotation axis and the inductive sensor is arranged to detect the changing distance between the surface and the inductive sensor.

The surface is a plane that is arranged in respect of the rotation axis of the component at an angle that differs from <NUM> degrees.

According to an embodiment of the invention, the component is a pulley, or an axle or shaft supporting a pulley.

According to an embodiment of the invention, the component or the measurement part is provided with an area of removed or added material for compensating the effect of the unsymmetrical shape of the component the inertial forces of the component or the measurement part.

According to an embodiment of the invention, the component comprises a drilling for compensating the effect of the unsymmetrical shape of the component or the measurement part on the inertial forces of the component or the measurement part.

According to an embodiment of the invention, the component is configured so that each angular position of the component about the rotation axis generates a unique output signal in the inductive sensor. This allows the absolute angular position of the component to be determined using a single inductive sensor.

A monitoring system according to the invention comprises a measurement arrangement defined above arranged to monitor the rotation speed of a component of an elevator.

An elevator according to the invention comprises a measurement arrangement defined above.

According to an embodiment of the invention, the elevator comprises a first measurement arrangement that is arranged to monitor the rotation speed of a pulley of an elevator car and a second measuring arrangement that is arranged to monitor the rotation speed of a pulley of a counterweight of the elevator. This allows for example detection of stalling of the elevator car or the counterweight.

Embodiments of the invention are described below in more detail with reference to the accompanying drawings, in which.

In <FIG> is shown schematically a simplified view of an elevator. The elevator comprises an elevator car <NUM> and a counterweight <NUM> which are configured to be moved in the vertical direction in a shaft <NUM>. For the sake of clarity, many parts of the elevator, such as guide rails for the elevator car <NUM> and the counterweight <NUM> have been omitted in <FIG>. The elevator car <NUM> is connected to the counterweight <NUM> via a hoisting member <NUM>. The hoisting member <NUM> can be, for example, a steel wire, a belt, such as a toothed belt or a flat belt, a carbon fiber rope or a coated rope. The elevator can comprise several hoisting members <NUM>.

The elevator car <NUM> and the counterweight <NUM> are connected to each other in such a way that they move to opposite directions in respect of each other. The elevator is further provided with a motor <NUM>. The motor <NUM> is preferably an electric motor. The motor <NUM> drives a sheave <NUM>. The sheave <NUM> can be connected to the motor <NUM> either directly or via a gear. As the sheave <NUM> rotates, the hoisting member <NUM> moves and the elevator car <NUM> and the counterweight <NUM> are moved. In the example of <FIG>, each end of the hoisting member <NUM> is fixed to the upper end of the shaft <NUM>. The elevator car <NUM> is provided with a first pulley 7a and a second pulley 7b. In the example of <FIG>, the pulleys 7a, 7b are arranged below the elevator car <NUM>. The hoisting member <NUM> is engaged with the first pulley 7a and the second pulley 7b. The pulleys 7a, 7b of the elevator car <NUM> are configured to rotate freely about a rotation axis. The counterweight <NUM> is provided with a pulley <NUM> which is engaged with the hoisting member <NUM>. Also the pulley <NUM> of the counterweight <NUM> is configured to rotate freely about a rotation axis. The sheave <NUM>, the pulleys 7a, 7b, <NUM> and the hoisting member <NUM> form the roping system of the elevator.

It should be noted that <FIG> shows only an example of a roping system of an elevator, and the hoisting member <NUM> could be arranged in many alternative ways. For example, the elevator car <NUM> could be provided with a single pulley. The counterweight <NUM> could be provided with more than one pulleys. A first end of the hoisting member <NUM> could be attached to the elevator car <NUM> and a second end of the hoisting member <NUM> could be attached to the counterweight <NUM>. The hoisting member <NUM> could be guided around the sheave <NUM> of the motor <NUM> twice.

In the example of <FIG>, the motor <NUM> is arranged in a machine room <NUM> which is located above the shaft <NUM>. However, the elevator could also be a machine-room-less elevator. The motor <NUM> could thus be arranged in the shaft <NUM>. The motor <NUM> could be arranged either at the upper end or at the lower end of the shaft <NUM>. The lower end of the shaft <NUM> is provided with at least one end buffer <NUM> for the elevator car <NUM> and at least one end buffer <NUM> for the counterweight <NUM>. The purpose of the end buffers <NUM>, <NUM> is to stop the elevator car <NUM> or the counterweight <NUM> if the elevator car <NUM> or the counterweight <NUM> descends beyond its normal moving range. The buffers <NUM>, <NUM> are configured to accumulate or dissipate the kinetic energy of the elevator car <NUM> or the counterweight <NUM> in case the elevator car <NUM> or the counterweight <NUM> hits the buffer <NUM>, <NUM> and thus limit the deceleration of the elevator car <NUM> or the counterweight <NUM> in such a situation. <FIG> also shows the doors <NUM> of the shaft <NUM> at the lowermost landing.

In elevators it is crucial to know precisely the speed and the position of the elevator car <NUM>. Speed information can be used, for example, to detect overspeed of the elevator, for controlled slowdown when the elevator car <NUM> approaches an end of the shaft <NUM>, or for detecting stalling of the elevator car <NUM> or the counterweight <NUM>. Position information is needed, for instance, when the elevator car <NUM> approaches an end of the shaft <NUM>. For monitoring the speed and position of various parts of the elevator, the elevator can be provided with different sensors and measurement arrangements. <FIG> shows a first measurement arrangement 20a which is arranged to measure the rotation speed of the first pulley 7a of the elevator car <NUM>. A second measurement arrangement 20b is arranged to measure the rotation speed of the pulley <NUM> of the counterweight <NUM>. A third measurement arrangement 20c is arranged to measure the rotation speed of the second pulley 7b of the elevator car <NUM>. <FIG> further shows a sensor <NUM> that is configured to detect that the elevator car <NUM> is at the lowermost landing and another sensor <NUM> that is configured to detect that the elevator car <NUM> is at the uppermost landing.

The rotation speed of a pulley 7a, 7b, <NUM> of the elevator car <NUM> or the counterweight <NUM> can be measured by means of a measurement arrangement according to the invention. The measurement arrangement according to the invention allows measurement of the rotation speed of a rotatable component of an elevator. The component is rotatable about a rotation axis. In an elevator, the rotatable component can be, for instance, a sheave, a pulley or an axle or shaft supporting such a pulley or sheave. The measurement arrangement comprises an inductive sensor that is arranged stationary in respect of the rotation axis of the component and adjacent to the component The component is configured as rotationally unsymmetrical about the rotation axis so that different angular positions of the component about the rotation axis generate different output signals in the inductive sensor.

The expression "inductive sensor" refers here to a sensor, which uses the principle of electromagnetic induction to detect the presence of a metallic object. The operation of a typical inductive sensor is based on creating an oscillating electromagnetic field by supplying alternating current to a coil. The presence of a metallic object causes changes in the frequency or current in the coil. These changes can be monitored either directly from the coil or using a second coil. The inductive sensor used in the arrangement according to the invention is configured to detect the magnitude of the changes in the electromagnetic field and to generate an output signal representing the changes in the electromagnetic field. The sensor can thus be used for example to determine a distance to a metallic object, instead of functioning as an on/off -type sensor. The inductive sensor can be a digital sensor.

The measurement arrangement according to the invention is reliable and inexpensive. By determining the rotation speed of a pulley 7a, 7b of an elevator car <NUM>, the speed of the elevator car <NUM> can be determined. By determining the rotation speed of a pulley <NUM> of a counterweight <NUM>, the speed of the counterweight <NUM> can be determined. Also the position of the elevator car <NUM> and/or the counterweight <NUM> can be determined based on the obtained speed data. Also the acceleration or deceleration of the elevator car <NUM> or the counterweight <NUM> can be determined.

<FIG> shows a measurement arrangement 20b according to a first embodiment of the invention. In the embodiment of <FIG>, the rotatable component is a pulley <NUM> of a counterweight. The pulley <NUM> is arranged around an axle <NUM>. The pulley <NUM> is configured to be rotatable about a rotation axis <NUM>. The axle <NUM> can be supported by means of at least one bearing and the pulley <NUM> can rotate with the axle <NUM>. Alternatively, the axle <NUM> can be stationary and the pulley <NUM> can rotate around the axle <NUM>. The pulley <NUM> could thus be supported by means of a bearing arranged on the axle <NUM>.

The measurement arrangement is provided with an inductive sensor <NUM>. In the embodiment of <FIG>, the inductive sensor <NUM> is arranged adjacent to the pulley <NUM>. One side surface <NUM> of the pulley <NUM> is configured so that the distance from the surface <NUM> to the inductive sensor <NUM> depends on the angular position of the pulley <NUM>. The side surface <NUM> is arranged in respect of the rotation axis <NUM> of the pulley <NUM> at an angle α which differs from <NUM> degrees. The angle α between the rotation axis <NUM> and the surface <NUM> can be, for instance, <NUM>-<NUM> degrees. The inductive sensor <NUM> is configured to produce an output signal that depends on the distance between the sensor <NUM> and the surface <NUM>. By determining the distance from the side surface <NUM> to the sensor <NUM>, the angular position of the pulley <NUM> can be determined. By monitoring the angular position of the pulley <NUM>, also the rotation speed of the pulley <NUM> can be determined.

Because the pulley <NUM> of the embodiment of <FIG> is not rotationally symmetrical, but the thickness of the pulley <NUM> in the axial direction of the pulley <NUM> varies, rotation of the pulley <NUM> creates inertial forces. In order to compensate the inertial forces caused by the varying thickness of the pulley <NUM>, the pulley <NUM> can be provided with a drilling <NUM>, as illustrated in <FIG>. In the embodiment of <FIG>, the drilling <NUM> extends inwards from the side surface <NUM> of the pulley <NUM> in the axial direction of the pulley <NUM>. However, the drilling <NUM> could also be arranged on the opposite side surface of the pulley <NUM>. Instead of or in addition to the drilling <NUM>, the pulley <NUM> could be provided with some other kind of an area of removed or added material for balancing the pulley <NUM>. For instance, the pulley <NUM> could be provided with a groove or a cutting on the thicker side, and/or with a protrusion or a counterweight on the thinner side of the pulley <NUM>.

<FIG> shows a measurement arrangement 20b according to a second embodiment of the invention. In the embodiment of <FIG>, the pulley <NUM> is supported by a rotatable axle <NUM>. The axle <NUM> is thus supported by means of at least one bearing (not shown). The pulley <NUM> is attached to the axle <NUM> in a rotationally fixed manner. The rotation speed of the pulley <NUM> thus equals the rotation speed of the axle <NUM>. Also the arrangement of <FIG> comprises an inductive sensor <NUM>. The inductive sensor <NUM> is arranged to monitor the distance to an end surface <NUM> of the axle <NUM>. In a similar way as in the embodiment of <FIG>, the end surface <NUM> of the axle <NUM> is arranged in respect of the rotation axis <NUM> of the pulley <NUM> at an angle α which differs from <NUM> degrees. The angle α between the rotation axis <NUM> and the surface <NUM> can be, for instance, <NUM>-<NUM> degrees. In the embodiment of <FIG>, the axle <NUM> is provided with a drilling <NUM> for balancing the axle <NUM>. In the embodiment of <FIG>, the drilling extends inwards from the end surface <NUM> of the axle <NUM> in the axial direction of the axle <NUM>.

However, the drilling could also extend radially inwards from the outer perimeter of the axle <NUM>. Instead of the drilling or in addition to it, the axle <NUM> could be provided with some other kind of an area of removed or added material, such as a cutting or a groove or a counterweight. The operating principle of the arrangement of <FIG> is similar to the operating principle of the arrangement of <FIG>. The angular position and the rotation speed of the pulley <NUM> correspond to the angular position and the rotation speed of the axle <NUM>, respectively. By determining the rotation speed of the axle <NUM>, the rotation speed of the pulley <NUM> can thus be determined.

<FIG> shows a measurement arrangement 20b not according to the invention. <FIG> shows an end view of the arrangement of <FIG> (inductive sensor not shown). In the arrangement of <FIG>, an assembly comprising a pulley <NUM> and an axle <NUM> is provided with a separate measurement part <NUM>, which is utilized in determination of the rotation speed of the pulley <NUM>. In the embodiment of <FIG>, the pulley <NUM> is attached in a rotationally fixed manner to the axle <NUM>. The measurement part <NUM> is attached in a rotationally fixed manner to the axle <NUM>. If the pulley <NUM> rotated relative to the axle <NUM>, the measurement part <NUM> would be attached in a rotationally fixed manner to the pulley <NUM>. The arrangement is provided with an inductive sensor <NUM> which is arranged to monitor the distance to the outer perimeter <NUM> of the measurement part <NUM>. The measurement part <NUM> is arranged around the axle <NUM> and it has a non-circular shape. The thickness of the measurement part <NUM> thus varies. As the axle <NUM> and the measurement part <NUM> rotate, the distance from the outer perimeter <NUM> of the measurement part <NUM> to the inductive sensor <NUM> varies. By monitoring the distance between the measurement part <NUM> and the sensor <NUM>, the rotation speed of the measurement part <NUM> and the pulley <NUM> can be determined. In the embodiment of <FIG>, each distance from the outer perimeter <NUM> of the measurement part <NUM> to the inductive sensor <NUM> corresponds to two angular positions of the pulley <NUM>. The absolute angular position of the pulley <NUM> can thus not be determined by means of the inductive sensor <NUM> alone. However, even in this embodiment the rotation speed of the pulley <NUM> can be determined. The absolute position of the pulley <NUM> could be determined, for instance, by providing the axle <NUM> with two measurement parts, measuring the distance from each measurement part to an inductive sensor, and combining the obtained information.

<FIG> shows a measurement arrangement 20b according to a third embodiment of the invention. <FIG> shows an end view of the arrangement of <FIG> (inductive sensor not shown). In the embodiment of <FIG>, an end surface <NUM> of the axle <NUM> is provided with a groove <NUM>. The groove <NUM> is circular and extends over a full turn. The groove <NUM> has a varying depth. An inductive sensor <NUM> is arranged to measure the distance to the bottom of the groove <NUM>. The groove <NUM> is configured so that each point along the groove <NUM> has an individual depth value. Each measured depth thus corresponds to a single point along the groove <NUM>. The groove <NUM> has a point of discontinuity 17a.

On a first side of the point of discontinuity 17a, the groove <NUM> has its greatest value. Going along the groove <NUM> away from the point of discontinuity the depth of the groove <NUM> decreases, and the depth of the groove <NUM> has it smallest value on a second side of the point of discontinuity 17a. Each measured distance from the inductive sensor <NUM> to the bottom of the groove <NUM> thus corresponds to a single angular position of the axle <NUM> and the pulley <NUM>. Instead of arranging the groove <NUM> in the axle <NUM>, the groove could also be arranged in the pulley <NUM>. The groove does not have to be on an end surface of the axle <NUM> or in the pulley <NUM>, but the groove could also be, for instance, on the outer perimeter of the axle <NUM>. Instead of having a varying depth, the groove <NUM> could have a varying width, and the inductive sensor <NUM> could be arranged to measure the distance to one of the side walls of the groove. A benefit of the arrangement of <FIG> is that each angular position of the pulley <NUM> corresponds to a certain unique distance from the bottom of the groove <NUM> to the inductive sensor <NUM>. The arrangement of <FIG> allows thus determining the absolute angular position of pulley <NUM> using a single inductive sensor <NUM>.

<FIG> shows a measurement arrangement not according to the invention. The arrangement is similar to the previous embodiments, in particular to the embodiments of <FIG> and <FIG>. As in the embodiment of <FIG>, an assembly comprising a pulley <NUM> and an axle <NUM> is provided with a separate measurement part <NUM> which is utilized in determination of the rotation speed of the pulley <NUM>. In the embodiment of <FIG>, the pulley <NUM> is attached in a rotationally fixed manner to the axle <NUM>. The measurement part <NUM> is attached in a rotationally fixed manner to the axle <NUM>. If the pulley <NUM> rotated relative to the axle <NUM>, the measurement part <NUM> would be attached in a rotationally fixed manner to the pulley <NUM>. The arrangement is provided with an inductive sensor <NUM> which is arranged to monitor the distance to a side surface <NUM> of the measurement part <NUM>.

The side surface <NUM> is arranged in respect of the rotation axis <NUM> of the pulley <NUM> at an angle which differs from <NUM> degrees. The angle between the rotation axis <NUM> and the surface <NUM> can be, for instance, <NUM>-<NUM> degrees. The inductive sensor <NUM> is configured to produce an output signal that depends on the distance between the sensor <NUM> and the surface <NUM>. By determining the distance from the side surface <NUM> to the sensor <NUM>, the angular position of the pulley <NUM> can be determined. The measurement part <NUM> of the embodiment of <FIG> can be provided with a drilling, cutting or counterweight for balancing inertial forces in a similar way as in the previous embodiments. A benefit of using a separate measurement part <NUM> is that the pulley <NUM> and the axle <NUM> do not have to be modified. The measurement arrangement could thus be applied to existing pulley-axle assemblies by adding a measurement part <NUM> and an inductive sensor <NUM>.

The measurement arrangement could also be configured in many alternative ways. For instance, the outer perimeter of the axle <NUM> or the pulley <NUM> could be made non-circular or a side surface of the pulley <NUM> could be provided with a groove. Although embodiments of the invention have been described in connection with the pulley <NUM> of the counterweight <NUM>, the rotation speed of a pulley of an elevator car <NUM> or a motor <NUM> can be measured in a similar way. In an escalator or a moving walkway, the rotation speed of a chain wheel could be monitored using a similar measurement arrangement not falling within the scope of the claims.

In the embodiments of <FIG>, <FIG> and <FIG>, each distance from the inductive sensor <NUM> to a monitored surface <NUM>, <NUM>, <NUM>, <NUM> corresponds to two angular positions of the pulley <NUM> or the axle <NUM>. The measurement data from the inductive sensor <NUM> can be combined with other data to determine the absolute angular position of the pulley <NUM> or the axle <NUM>. For instance, two inductive sensors <NUM> can be used to measure the distance to two different surfaces in accordance with different embodiments of the invention, and by combining the data from the sensors <NUM>, the absolute angular position of the pulley <NUM> can be determined. Alternatively or in addition to that, data from some other sensor, such as a sensor detecting that the elevator car <NUM> is at a certain landing, can be used for complementing the data provided by the inductive sensor <NUM>.

The measurement arrangement according to the invention can be utilized in many different ways. <FIG> shows schematically an elevator comprising a first measurement arrangement 20a, a second measurement arrangement 20b and a third measurement arrangement 20c. <FIG> shows a monitoring system comprising the first, second and third measurement arrangements 20a, 20b, 20c.

The first measurement arrangement 20a is arranged to measure the rotation speed of a pulley 7a of an elevator car <NUM>. Based on the measurement data from the first measurement arrangement 20a, the speed and/or position of the elevator car <NUM> can be determined. The second measurement arrangement 20b is arranged to measure the rotation speed of the pulley <NUM> of the counterweight <NUM>. Based on the measurement data from the second measurement arrangement 20b, the speed and/or position of the counterweight <NUM> can be determined. The measurement data from the second measurement arrangement 20b may be compared to the measurement data from the first measurement arrangement 20a. Alternatively, the speed of the counterweight <NUM> determined on the basis of the measurement data can be compared to the speed of the elevator car <NUM>. A speed difference can be an indication of a stalling situation, where the elevator car <NUM> or the counterweight <NUM> is ascending at a desired speed whereas the descending part is stopped due to reaching the bottom of the shaft <NUM> or due to jamming. This causes slackening of the hoisting member <NUM>. The movement of the elevator car <NUM> or the counterweight <NUM> may continue until it reaches the upper end of the shaft <NUM> or until the friction force of the hoisting member <NUM> against the sheave <NUM> of the motor <NUM> is insufficient to maintain the movement of the ascending part. Both situations are dangerous, as hitting of the upper end of the shaft <NUM> may cause significant damage and disappearing of the friction force between the sheave <NUM> and the hoisting member <NUM> causes free fall of the elevator car <NUM> or the counterweight <NUM>.

The third measurement arrangement 20c is arranged to measure the rotation speed of another pulley 7b of the elevator car <NUM>. The third measurement arrangement 20c can be used as a back-up for the first measurement arrangement. Measurement data from the first measurement arrangement 20a can also be compared to measurement data from the third measurement arrangement 20c. In case the comparison indicates a speed difference between the first pulley 7a and the second pulley 7b, the hoisting member <NUM> may be slipping on one of the pulleys 7a, 7b. This may be an indication of a bearing failure and a warning signal may be generated.

<FIG> shows the inductive sensors <NUM> of the measuring arrangements 20a, 20b, 20c connected to a control unit <NUM>. Also the sensors <NUM>, <NUM> detecting whether the elevator car <NUM> is at a certain landing are connected to the control unit <NUM>. A signal from a sensor <NUM>, <NUM> detecting the presence of the elevator car <NUM> at a certain landing can be used as a reference point, and by using measurement data from the first or the third measuring arrangement 20a, 20c, the vertical position of the elevator car <NUM> can be determined even between the landings. This allows, for example, calculating the distance of the elevator car <NUM> to the end buffer <NUM> or to the upper end of the shaft <NUM>. The determined distance and the speed of the elevator car <NUM> can be used as inputs for speed control of the elevator car <NUM> as the elevator car <NUM> approaches one end of the shaft <NUM>. This helps ensuring that the deceleration of the elevator car <NUM> does not exceed predetermined limit values.

A measurement arrangement not falling within the scope of the claims could also be used for measuring the rotation speed of the sheave <NUM> driven by the motor <NUM>. The measurement data could be compared to the rotation speed of a pulley 7a, 7b of the elevator car <NUM> and/or the pulley <NUM> of the counterweight <NUM>. Also the speed of the hoisting member <NUM> could be determined on the basis of the measurement data and compared to the speed of the elevator car <NUM> and/or the counterweight <NUM>. A speed difference can be an indication of slipping of the hoisting member <NUM> on the sheave <NUM> driven by the motor <NUM> or jamming of a bearing of a pulley 7a, 7b, <NUM> of the elevator car <NUM> or the counterweight <NUM>. By comparing the rotation speed of the sheave <NUM> driven by the motor <NUM> and the rotation speed of a pulley 7a, 7b, <NUM> of the elevator car <NUM> and/or the counterweight <NUM>, also certain overspeed situations could be detected. It is not necessary that all the rotation speeds are determined using a measuring arrangement according to the invention, but it is possible to combine data from different sources. For instance, the rotation speed of a pulley 7a, 7b, <NUM> of the elevator car <NUM> or the counterweight <NUM> could be determined by means of a measuring arrangement according to the invention, but the rotation speed of the sheave <NUM> driven by the motor <NUM> could be determined based on the rotation speed of the motor <NUM>.

Claim 1:
A measurement arrangement (20a, 20b, 20c) for measuring the rotation speed of a component (<NUM>, 7a, 7b, <NUM>, <NUM>) that is attached to an elevator car (<NUM>) or to a counterweight (<NUM>) of an elevator, wherein the component (<NUM>, 7a, 7b, <NUM>, <NUM>) is rotatable about a rotation axis (<NUM>), the arrangement comprises an inductive sensor (<NUM>) that is arranged stationary in respect of the rotation axis (<NUM>) of the component (<NUM>, 7a, 7b, <NUM>, <NUM>) and adjacent to the component (<NUM>, 7a, 7b, <NUM>, <NUM>) and the component (<NUM>, 7a, 7b, <NUM>, <NUM>) is configured as rotationally unsymmetrical about the rotation axis (<NUM>) so that different angular positions of the component (<NUM>, 7a, 7b, <NUM>, <NUM>) about the rotation axis (<NUM>) generate different output signals in the inductive sensor (<NUM>), wherein the component (<NUM>, 7a, 7b, <NUM>, <NUM>) is provided with a surface (<NUM>, <NUM>) that is shaped and/or positioned so that the distance from the surface (<NUM>, <NUM>) to the inductive sensor (<NUM>) changes as the component (<NUM>, 7a, 7b, <NUM>, <NUM>) rotates about the rotation axis (<NUM>) and the inductive sensor (<NUM>) is arranged to detect the changing distance between the surface (<NUM>, <NUM>) and the inductive sensor (<NUM>), and wherein the surface (<NUM>, <NUM>) is a plane (<NUM>, <NUM>) that is arranged in respect of the rotation axis (<NUM>) of the component (<NUM>, 7a, 7b, <NUM>, <NUM>) at an angle (α) that differs from <NUM> degrees.