CN217032679U

CN217032679U - Measuring device for monitoring a liquid level in a machine or system

Info

Publication number: CN217032679U
Application number: CN202220371817.XU
Authority: CN
Inventors: F·斯托尔; C·埃尔威恩
Original assignee: Kriwan Industrie Elektronik GmbH
Current assignee: Kriwan Industrie Elektronik GmbH
Priority date: 2021-02-24
Filing date: 2022-02-21
Publication date: 2022-07-22
Anticipated expiration: 2032-02-21
Also published as: DE102021104356A1

Abstract

A measuring device for monitoring a liquid level in a machine or system, having: a housing having a thread for screwing the housing into the compressor and provided with a chamber which, in the screwed-in state of the housing, is in fluid connection with a fluid region of the machine or system to be examined; and a float body arranged in the chamber, which rotates about a rotational axis as a function of a liquid level in the chamber, and which has a magnetic signal transmitter which interacts with a magnetic field sensor arranged outside the chamber in order to detect a position and/or a rotation of the magnetic signal transmitter, wherein the float body is arranged in the chamber in such a way that, in the absence of fluid in the chamber, the float body is oriented in a predefined basic position by gravity, independently of a screwing-in rotational position of the housing which occurs when the housing is screwed into the machine or system, and wherein the magnetic field sensor for detecting the rotational position of the magnetic signal transmitter is arranged in extension of the rotational axis.

Description

Measuring device for monitoring a liquid level in a machine or system

Technical Field

The present invention relates to a measuring device for level monitoring in a machine or system.

Background

Typical fields of application for such measuring devices are oil level monitoring in compressors, motors or pumps, but also liquid level monitoring in refrigeration systems or pump systems.

Measuring devices for level monitoring are usually screwed into the machine or system to be monitored, so that the measuring device is in fluid connection with the liquid region to be monitored in the screwed state. In the simplest case, only the viewing window enabling visual inspection of the liquid level is screwed on. For automatic (liquid) level monitoring, however, measuring devices are used which instead of viewing windows are screwed into the machine or system. A measuring device for monitoring the oil level, which operates according to the optical measuring principle, is known from DE 102016115228 a 1. It is thus possible to reliably determine whether a sufficient filling level is present. Measuring devices for level monitoring are known from EP 2589898B 1 and KR 1020010029447 a, which have a float arranged in a chamber, which is oriented according to the liquid level in the chamber, and which have a magnetic signal transmitter. A magnetic field sensor is provided outside the chamber for detecting the position and/or rotation of the magnetic signal emitter. The floating body is arranged to be able to oscillate around the axis of rotation within an angular range of about 90 deg.. In the measuring device known from practice according to EP 2589898B 1, only three horizontal regions can be distinguished thereby.

However, the disadvantages of both known measuring devices are: they cannot be screwed directly into an internal thread of a machine or system, but rather require an adapter device to ensure a predetermined orientation of the measuring device in the screwed-in state.

US 20170038241 a 1D 1 discloses a measuring device for liquid level monitoring, which has a freely rotatable float body in which a magnetic material is embedded. In the outer ring, a sensor section is provided, which has a switch that can be adjusted between an open position and a closed position, which switch is responsive to the magnetic material of the float 60.

Furthermore, US 9318286B 2 shows a liquid level sensor with a float body which follows the gravitational direction independently of the screwed-in position of the housing. The interior of the housing is connected to the fluid region to be monitored by means of a plurality of openings provided.

SUMMERY OF THE UTILITY MODEL

The object of the present invention is therefore to provide a measuring device for level monitoring in machines or systems which makes it possible to simplify the assembly and to continuously detect the liquid level.

According to the utility model, this task is solved by a measuring device for level monitoring in a machine or system, characterized by the following features:

a housing having a thread for screwing the housing into the compressor,

a chamber arranged in the housing, which chamber is in fluid connection with a fluid region of the machine or system to be monitored in the screwed-in state of the housing,

a float arranged in the chamber, oriented according to the liquid level in the cavity and having a magnetic signal emitter, and

a magnetic field sensor arranged outside the chamber for detecting the position and/or rotation of the magnetic signal emitter,

wherein the floating body is arranged in the chamber in such a way that, in the absence of liquid in the chamber, the floating body is oriented in a predefined basic position by gravity, irrespective of the screwing-in rotational position of the housing which occurs when the housing is screwed into the machine or system, and

-wherein the magnetic field sensor for detecting the rotational position of the magnetic signal transmitter is arranged on an extension of the rotational axis.

Since the float can be automatically oriented into the predefined basic position under the influence of gravity, irrespective of the screwed-in rotational position of the housing, it is no longer necessary to fasten the measuring device on or in the machine or system using the adapter means, so that the assembly is more economical and simpler. By arranging the magnetic field sensor on an extension of the axis of rotation, the magnetic field sensor detects the rotational position of the signal emitter, wherein an accuracy of up to +/-5 °, preferably up to +/-2.5 °, can be achieved. In this way, the liquid level can be detected continuously also with minimal changes.

The magnetic signal transmitter preferably has a permanent magnet. The magnetic field sensor is preferably formed by a hall sensor.

According to a further embodiment, the chamber is delimited by a cylindrical wall, an end wall and an opposite end side, wherein, in the screwed-in state of the housing, a fluid connection with the machine or system is established by the opposite end side. In this case, it can also be provided that the opposing end sides are provided with a grating or filter in order to prevent magnetic particles from reaching the cavity and depositing in the region of the magnetic signal transmitter. Furthermore, a grating or a filter is used to delimit the movement space of the floating body, so that the floating body does not fall out of the chamber.

According to a preferred first embodiment of the utility model, the floating body is placed in the chamber freely rotatable 360 ° about an axis of rotation coinciding with the longitudinal axis of the screw thread or about an axis of rotation oriented parallel to the longitudinal axis of the screw thread. The fact that the float is freely rotatably placed in the chamber also doubles the measuring range of the liquid level with respect to the known solutions, since the float can detect the liquid level with a rotation angle of 180 °.

In order to allow the floating body to be automatically oriented into a predefined basic position in the absence of fluid in the chamber, the center of gravity of the floating body is arranged at a suitable distance from the axis of rotation.

According to a further embodiment of the first exemplary embodiment, the magnetic signal transmitter is arranged in the buoyant body in a rotationally symmetrical manner about the axis of rotation. Here, in particular, the magnetic signal transmitter may be formed as a radially magnetized ring magnet.

In the direction of the longitudinal axis of the thread, the chamber has a first half with an end wall and a second half with a grating or filter, wherein the float is preferably arranged in the first half, since this region is further away from the grating or filter, so that the attraction effect on possible magnetic particles in the fluid is also correspondingly greatly reduced. Since the fluid in the machine or system is always constantly moving during operation, possible magnetic particles are also immediately carried over again.

According to a further embodiment of the utility model, the float body can be formed asymmetrically with respect to a sectional plane which is enclosed by the axis of rotation and the center of gravity of the float body. The advantages are that: in the case of a rising liquid level, the float body rotates in a predetermined direction of rotation at all times due to the buoyancy of the float body region immersed in the fluid.

In a second embodiment of the utility model, the floating body is loosely arranged in the chamber, the floating body sliding or rolling at the cylindrical wall following gravity during the screwing movement of the housing, thereby occupying the lowest (deepest) position in the chamber. In this case, it is advantageous if the float body has a round, rounded or partially spherical outer contour in order to reduce friction effects with the cylindrical wall and to facilitate the orientation of the float body in the desired basic position. Once the chamber is filled with fluid, in particular oil, during operation, possible friction between the floating body and the cylindrical wall is further reduced by the lubricating effect of the fluid.

According to another design configuration of this embodiment, the length of the floating body is less than 100% but more than 90% of the length of the cylindrical wall. This ensures that the float cannot twist in the chamber and thus falsify the measurement result. Furthermore, the magnetic field sensor is oriented relative to the magnetic signal transmitter in the float such that it detects the height position of the float due to the fluid level.

Drawings

Other design configurations of the present invention are further explained in light of the following description and accompanying drawings.

Shown in the drawings:

FIG. 1 is a schematic longitudinal sectional view of a measuring device according to a first embodiment;

figure 2 is a cross-sectional view of the first embodiment in the region of the floating body without fluid in the chamber,

figure 3 is a cross-sectional view of the first embodiment in the region of the floating body in the presence of a fluid in the chamber,

figure 4 is a schematic three-dimensional view of a magnetic signal emitter and a magnetic field sensor,

figure 5 is a characteristic curve of the output signal of the magnetic field sensor as a function of the rotational position of the magnetic signal emitter,

figures 6 a-6 i are schematic cross-sectional views of different deformations of the floating body,

figure 7a is a diagram of force vectors according to an example of the floating body of figure 6g in the absence of fluid in the chamber,

FIG. 7b is a diagram of force vectors according to an example of the floating body of FIG. 6g in the presence of a specific liquid level within the chamber;

FIG. 8 is a schematic longitudinal sectional view of a measuring device according to a second embodiment;

figure 9 is a cross-sectional view of the second embodiment in the region of the floating body without fluid in the chamber,

figure 10 is a cross-sectional view of the second embodiment in the region of the floating body in the presence of a fluid in the chamber,

fig. 11 is a schematic longitudinal sectional view of a measuring device according to a third embodiment.

Detailed Description

Fig. 1 to 3 show a measuring device for level monitoring in a machine or system according to a first embodiment. The device has a housing 1, which housing 1 consists of a sensor part 1a, a threaded part 1b and an intermediate part arranged between the two. The threaded part 1b has a thread 2 formed as an external thread, by means of which the measuring device can be screwed into a correspondingly formed internal thread and thus into a machine or system. The middle part 1c has a hexagonal outer contour so that the housing can be screwed in by means of a corresponding wrench.

In the region of the threaded portion 1b, a chamber is formed internally, which is delimited by a cylindrical wall 3a, an end wall 3b and an opposite end side 3 c. In the exemplary embodiment shown, the opposite side 3c is closed by means of a filter or a grating 4, but is formed such that, in the screwed-in state of the measuring device, a fluid connection to the fluid region of the machine or system to be monitored is ensured by this grating 4. Inside the chamber 3a floating body 5 is placed which is free to rotate 360 deg. around a rotation axis 6. The axis of rotation 6 coincides here with the longitudinal thread axis 2a of the thread 2.

Fig. 2 shows a cross section of the floating body 5, wherein the floating body 5 has a center of gravity 5a, which is arranged at a distance from the axis of rotation. This means that in the absence of fluid in the chamber 3, the floating body 5 follows a gravitational orientation such that the axis of rotation 6 and the centre of gravity 5a are located on the vertical 7. The thread 2 is provided on the outside of a cylindrical wall 3a fixed at the housing 1, so that the housing 1 will rotate together when the measuring device is screwed into a machine or system. The floating body 5 is mounted on the axis of rotation 6 so as to be freely movable in rotation, as shown in fig. 2, the floating body 5 always following the gravitational orientation in this case. Regardless of the rotated position of the housing 1, it therefore always assumes the basic position, which is specified in fig. 2, in relation to the vertical 7.

Fig. 2 also shows that the hull 5 is formed asymmetrically with respect to a cross-sectional plane spanned by the axis of rotation 6 and the center of gravity 5 a. This entails that the floating body is subjected to buoyancy forces when the liquid level rises, which buoyancy forces deflect the floating body in a preferred direction of rotation. In the first embodiment shown, the rotation occurs clockwise, as shown in fig. 3. The forces acting in the region of the floating body will be explained in more detail below with reference to fig. 7a and 7 b.

In the first embodiment shown, the floating body 5 is essentially constituted by a first cylinder 5b, a second cylinder 5c and a lever arm 5d connecting the two cylinders. The first cylinder 5b is arranged here in a rotationally symmetrical manner about the axis of rotation 6. The second cylinder 5c is formed smaller in diameter and is connected asymmetrically to the first cylinder 5b via a lever arm 5 d. A magnetic signal transmitter 9 is arranged inside the cylindrical body 5b of the floating body 5, the magnetic signal transmitter 9 here being formed as a radially magnetized ring magnet. This magnetic signal transmitter 9 is fixedly connected to the floating body 5 so that it rotates together with the floating body 5 in the event of a rise in the level of the fluid 8. The hull is formed, for example, as a plastic injection-molded item, in which the magnetic signal emitter 9 is embedded. The arrangement of the magnetic signal emitter 9 around the rotation axis 6 has the advantage that: the weight influence of the magnetic signal emitter 9 has little or no influence, since the weight force of the magnet and the cylinder 5b is absorbed and does not have to be compensated for by the buoyancy force caused by the second cylinder 5c and the lever arm 5 d.

In the sensor part 1a of the housing 1 there is also arranged a magnetic field sensor 10 which detects the rotational position of the magnetic signal transmitter 9. This magnetic field sensor 10 is formed, for example, as a hall sensor and is arranged in the extension of the axis of rotation 6, wherein it outputs a voltage signal which is dependent on the rotational position of the magnetic signal transmitter 9 and which has a sinusoidal course over an angular range of 360 °, as shown in more detail in fig. 5. In the present application, however, the floating body is rotated only in the range of 0 to 180 °. In the present embodiment, the magnetic field sensor 10 is formed as an x-y sensor, which generates two voltage values for each angular position of the magnetic sensor 9, which enable an unambiguous evaluation of the angular position of the magnetic sensor 9.

By the axial arrangement of the magnetic field sensor 10 with respect to the magnetic signal transmitter 9, the angular change of the hull 5 can be detected with an accuracy of +/-2.5 °. The voltage value of the magnetic field sensor 10 can then be converted to the level of the fluid 8 in the chamber 5 by a corresponding evaluation. This high resolution enables the detection of the liquid level to be very accurate and continuous.

However, instead of a ring magnet, a cube-shaped permanent magnet can also be used for the magnetic signal transmitter, which is arranged outside the rotational axis 6 of the hull 5. Furthermore, it is also conceivable to change the outer shape of the floating body 5. According to figures 6a to 6g different variants of floating bodies are shown, each of which can be placed in the chamber freely rotating around the rotation axis 6.

Fig. 6a shows a floating body 5.1 formed in the shape of a rectangular parallelepiped, which also has a magnetic signal transmitter 9.1 formed in the shape of a rectangular parallelepiped, which is embedded in the floating body 5.1 at a distance from the axis of rotation 6. The float 5.2 shown in fig. 6b is formed in the shape of a drop and likewise has a rectangular parallelepiped-shaped magnetic signal transmitter 9.2. The variant according to fig. 6c has a triangular float body 5.3, the float body 5.3 having a cuboid-shaped magnetic signal transmitter 9.3. The variants shown in figures 6a, 6b and 6c are formed symmetrically so that there is no preferred direction of rotation in the event of an ascending fluid 8 in the chamber. However, it is still possible to identify the direction of rotation in which the float is rotating during the evaluation, and then take the direction of rotation into account when calculating the liquid level.

However, a preferred direction of rotation of the hull may be forced in this way: using an asymmetrical shape of the hull or arranging the magnetic signal emitter and/or the rotation axis outside the symmetry axis. Combinations of these measures are of course also conceivable. The floating body 5.4 according to fig. 6d substantially corresponds to the triangular design according to fig. 6c, however with an angle cut out, so that the floating body 5.4 has an asymmetrical shape and thus rotates clockwise. The float element 5.5 of fig. 6e corresponds essentially to the float element according to fig. 6a, wherein the float element 5.5 formed in the shape of a cuboid also lacks an angle, which in turn results in a preferred direction of rotation in the clockwise direction.

Fig. 6f shows a floating body 5.6, the axis of rotation 6 of which does not lie in a plane of symmetry. This measure also produces a preferred direction of rotation in the clockwise direction in the event of a rising liquid level. Furthermore, the magnetic signal transmitter 9.6 can also be arranged asymmetrically with respect to the outer contour of the float 5.6.

The floating body 5.7 in the exemplary embodiment according to fig. 6g has an asymmetrical outer contour. It is formed essentially by a lever arm 5.7a, the lever arm 5.7a being supported at its upper end about a rotational axis 6. A cylindrical portion 5.7b is eccentrically mounted at the end of the lever arm 5.7a remote from the axis of rotation 6. A magnetic signal emitter 9.7 is also located in this cylindrical part.

A similar variant is shown in fig. 6h, however, where the magnetic signal transmitter 9.8 is arranged in the lever arm 5.8a of the hull 5.8. Furthermore, a cavity 5.8c is provided in the cylindrical part 5.8b, which cavity is closed in a fluid-tight manner, for example by a welded or pressed lid. The bubble enclosed in the cavity 5.8d increases the buoyancy force because the mass of the cylindrical part 5.8b is reduced by the cavity 5.8d and the magnetic signal emitter 9.8 moving into the lever arm 5.8 a.

The floating body 5.9 in fig. 6i differs from the variant of fig. 6g in that: the magnetic signal transmitter 9.9 is in turn arranged in the lever arm 5.9a, and more precisely at the end of the lever arm 5.9a facing away from the cylinder 5.9 b. The axis of rotation 6 is thereby arranged between the cylindrical body 5.9b and the magnetic signal transmitter 9.9, so that the magnetic signal transmitter 9.9 acts as a counterweight and thereby facilitates the rotation of the hull 5.9. The weight distribution of the floating body 5.9 is selected such that the center of gravity 5.9c of the floating body 5.9 is located between the axis of rotation 6 and the cylindrical portion 5.9b, thereby ensuring a desired orientation of the floating body 5.9 in the absence of fluid.

With the aid of the float body 5.7 of fig. 6g, the forces acting on the float body in the case of a specific liquid level in a predefined basic position which arises after screwing the measuring device into the machine or system are explained below. The predefined basic position is produced by the mass distribution of the hull and the position of the axis of rotation 6. In the resulting, predefined basic position, the floating body 5.7 hangs down on the axis of rotation 6, wherein the axis of rotation 6 and the center of gravity 5.7c of the floating body 5.7 lie on the vertical 7 (fig. 7a) the gravitational force G also acts in the center of gravity 5.7 c. In case of a rising liquid 8, the floating body 5.7 will at a certain moment be caught (contacted) by the liquid 8, so that in addition to the downward gravitational force G there is an upward acting buoyancy force F_AActing on the floating body 5.7, the buoyancy force F_AActing in the center of gravity of the immersion volume of the hull 5.7. Due to the asymmetrical design of the floating body 5.7, the center of gravity of the immersion volume is on the left side of the vertical line 7 in the figures according to fig. 7a and 7b, so that in the case of a horizontal rise of the liquid 8 the floating body rotates in the clockwise direction about the axis of rotation 6. The position of the magnetic signal transmitter 9.7 changes, the resulting magnetic field change being detected by the magnetic field sensor 10.

A second embodiment of the measuring device according to the utility model is shown in fig. 8 to 10, which differs from the first embodiment only in the type and placement of the floating body 11. In the present exemplary embodiment, the floating body 11 is arranged loosely in the chamber 3, wherein during the screwing-in movement of the housing 1 it slides down at the cylindrical wall 3a following the force of gravity. At the end of the screwing movement, the floating body 11 is in the deepest (lowest) position according to fig. 9. In the embodiment shown, the floating body 11 is formed elongated and has a lenticular cross-section. The length of the floating body 11 is less than 100% but greater than 90% of the length of the cylindrical wall 3 a. In this way it is ensured that the floating body cannot rotate within the chamber.

Fig. 10 shows the floating body 11 floating due to the action of the fluid 8. A rod or cuboid magnet is arranged inside the floating body 11, the varying height position/positioning of which is detected and converted by the magnetic field sensor 10. In the second embodiment, the fluid level is converted into a linear movement of the floating body 11, unlike the rotating floating body in the first embodiment.

Finally, fig. 11 shows a third embodiment, in which the floating body 12 is designed as a (one-end-enlarged) ball-stick, wherein the part 12a facing the end wall 3b is designed as a ball and the part 12b facing the grating 4 is designed as a rod. The magnetic signal transmitter 9 is here arranged in the bulb 12 a. The bulb has the main characteristics of: during the screwing movement of the measuring device, it rolls without problems at the cylindrical wall 3a and at the deepest (lower) point at the end of the screwing movement. Thus, in this embodiment, a clearly defined, predetermined basic position when no liquid is present in the chamber is produced. The chamber length is advantageously greater than the diameter. Furthermore, the length of the float body 12 is slightly smaller than the length of the cylindrical wall, so that it is again ensured that the float body is always oriented identically and the ball always remains in close proximity to the end wall 3 b. As the fluid rises, the float correspondingly floats, thereby changing the position of the magnetic signal emitter 9 relative to the magnetic field sensor 10.

The magnetic signal transmitter 9 is arranged with its north-south pole axis in the longitudinal axis of the hull 12. Thereby, one pole of the magnetic signal emitter 9 is directed to the tip of the spherical portion 12a on the extension of the rod-shaped portion 12b, and thus to the direction of the magnetic field sensor 10. The measurement is thus independent of the rotational position of the hull 12 about its longitudinal axis.

In all embodiments, the float body is configured in terms of material such that it can float without problems and thus fulfills its function as a float body. Plastic is a particularly suitable material, wherein the float can be manufactured as a plastic injection-molded part, into which the magnetic signal transmitter 9 is embedded. The housing 1 is made of a non-magnetic material, preferably a metal, such as brass or aluminum, so as to enable detection of magnetic field variations in the region of the magnetic field sensor 10. Furthermore, it is advantageous that the magnetic signal transmitter 9 is arranged in a region of the floating body in which the half of the chamber with the end wall 3b is arranged. As a result, the suction force acting on the magnetic signal transmitter 9 in the region of the grating 4 has been reduced considerably, so that the influence on possible components located in the fluid of the machine or system is correspondingly reduced.

The central portion 1c of the housing forms a partition wall between the chamber 3 and the magnetic field sensor 10 and must be designed such that the magnetic signal emitter 9 can co-act with the magnetic field sensor 10 to detect a position or a rotational position. The signal originating from the magnetic signal transmitter 9 must therefore be detectable by the magnetic field sensor 10 in a sufficient amount (intensity).

Otherwise, the wall thickness of the housing 1 is selected such that it can withstand the permissible operating pressure/burst pressure of the machine or system.

Of course, the utility model is not limited to the embodiments shown in the figures. Instead, it is essential that at the end of the screwing-in process, the floating body is already oriented in a defined, predetermined basic position, irrespective of the screwing-in rotational position of the housing. This can be achieved by: the floating body can rotate freely about the axis of rotation, or the floating body is loosely arranged in the chamber, wherein by its shape, following gravity, the floating body is oriented in the deepest (lower) point in the chamber.

For example, compressors, in particular refrigerant compressors, or pumps or motors are used as machines. The fluid is in particular oil. However, the measuring device may also be used in other systems in which the filling level of the fluid is to be monitored. In this case, for example, a cooling system can be used, in which the feed level (feed height) of the refrigerant is monitored. Furthermore, the measuring device can also be used for pumps or pump systems which operate according to the filling level of the fluid.

Claims

1. A measuring device for monitoring a liquid level in a machine or system, having:

-a housing (1), the housing (1) having a thread (2) for screwing the housing (1) into a machine or system,

-a chamber (3) provided in the housing (1), which chamber is in fluid connection with a fluid region of the machine or system to be monitored in a screwed-in state of the housing (1),

a float (5, 11, 12) arranged in the chamber (3), which float is oriented according to the liquid level in the chamber (3) and has a magnetic signal emitter (9),

-a magnetic field sensor (10) arranged outside the chamber (3) for detecting the position and/or rotation of the magnetic signal emitter (9),

wherein the float (5, 11, 12) is arranged in the chamber (3) in such a way that, in the absence of fluid (8) in the chamber (3), the float is oriented in a predefined basic position by gravity, irrespective of the screwing-in rotational position of the housing (1) which occurs when the housing (1) is screwed into the machine or system,

characterized in that the magnetic field sensor (10) is arranged in extension of the rotation axis (6) for detecting the rotational position of the magnetic signal emitter (9).

2. Measuring device according to claim 1, characterized in that the magnetic signal transmitter (9) has at least one permanent magnet.

3. A measuring device as claimed in claim 1, characterized in that the magnetic field sensor (10) is formed by a hall sensor.

4. A measuring device as claimed in claim 1, characterized in that the chamber is delimited by a cylindrical wall (3a), an end wall (3b) and an opposite end side (3c), wherein, in the screwed-in state of the housing (1), a fluid connection with the machine or system is produced by the opposite end side (3 c).

5. A measuring device according to claim 4, characterized in that the opposite end sides (3c) are provided with a grating (4) or a filter for preventing magnetic particles from intruding into the chamber (3).

6. A measuring device as claimed in claim 5, characterized in that the thread (2) has a thread longitudinal axis and the floating body (5) can be placed in the chamber (3) freely rotatable 360 ° about a rotation axis (6) coinciding with the thread longitudinal axis or about a rotation axis (6) oriented parallel to the thread longitudinal axis.

7. A measuring device as claimed in claim 6, characterized in that the magnetic signal transmitter (9) is arranged in the float (5) rotationally symmetrically about the axis of rotation (6).

8. A measuring device as claimed in claim 7, characterized in that the magnetic signal transmitter (9) is designed as a radially magnetized ring magnet.

9. A measuring device as claimed in claim 6, characterized in that the floating body (5) has a centre of gravity (5a) located outside the axis of rotation (6).

10. A measuring device as claimed in claim 9, characterized in that the floating body is designed asymmetrically with respect to a cross-sectional plane spanned by the axis of rotation (6) and the center of gravity (5 a).

11. A measuring device as claimed in claim 6, characterised in that the chamber (3) comprises, in the direction of the thread longitudinal axis, a first half with the end wall (3b) and a second half with the grating (4) or filter, wherein the floating body (5) is arranged in the first half.

12. A measuring device as claimed in claim 5, characterised in that the floating body (11, 12) is arranged loosely in the chamber (3) and slides or rolls down the cylindrical wall (3a) following gravity during the screwing-in movement of the housing.

13. A measuring device as claimed in claim 12, characterized in that the length of the float (11, 12) is less than 100% but more than 90% of the length of the cylindrical wall (3 a).

14. A measuring device as claimed in claim 12, characterized in that the magnetic field sensor (10) is designed for detecting the height position of the floating body (11, 12) due to the fluid level.