Sensor and method for determining a process parameter of a medium

Abstract

Sensor (1) for determining a process variable, in particular a fill level, limit level, density or viscosity, of a medium (2), comprising a measuring unit (6) attached to a sensor housing (5) that is at least partially surrounded by the medium (2) for determining the process variable of the medium (2), characterized in that at least one turbine wheel (12, 12', 12'', 12''') driving an electric generator (11) is rotatably mounted on the sensor housing (5) about an axis of rotation (13, 13') such that the at least one turbine wheel (12, 12', 12'', 12''') can be set into rotation by the medium (2) surrounding the sensor housing (5), and the turbine wheel is attached at a distal end of the sensor housing in the immediate vicinity of the measuring unit arranged at the distal end, wherein the distal end of the sensor housing is to be understood as a housing end that is surrounded by the medium and is connected to a proximal, fixed opposite the end of the sensor housing.

Description

[0001] The invention relates to a sensor for determining a process variable, for example a fill level, limit level, density or viscosity, of a medium, in particular a sensor with a sensor housing and a measuring unit attached thereto, and a method for determining such a process variable by means of such a sensor.

[0002] Sensors, particularly those used for level / fill level monitoring, are generally well-known. For example, such sensors can be designed as vibronic sensors (also known as vibration sensors), although this is not the only possible design. Other types of sensors for detecting, for example, a limit or fill level, density, viscosity, etc., of a medium are also included here. It is known that vibration sensors can have piezoelectric or inductive actuators.

[0003] A conventional vibration sensor also includes a diaphragm that can be excited to vibrate via a drive mechanism. This diaphragm, in turn, excites a mechanical oscillator mounted on it. Depending on the degree of coverage of the mechanical oscillator with a medium or material, as well as the viscosity and density of this medium / material, the mechanical oscillator vibrates at a characteristic frequency that can be detected by the vibration sensor and converted into a measurement signal.

[0004] For example, in DE 10 2017 112 167 A1, the applicant describes a vibration level sensor with an inductive drive. Particularly advantageous piezoelectric drives for vibration sensors are also described in further applications of the applicant which were not yet published at the time of the present application and are otherwise generally known in other embodiments.

[0005] Factors that can significantly interfere with the measurement results of such sensors, e.g., vibration sensors, include high ambient temperatures, for example greater than 150 °C or even greater than 300 °C, as well as turbulent flows of the medium to be measured by the sensor, e.g., vibration sensor.

[0006] In principle, sensors of this type require an electrical power supply to operate, powering electrical sensor components such as an electronic measuring unit, control unit, and / or evaluation unit. Depending on the measurement location, this power supply can also be provided by a battery. In this case, however, a certain amount of monitoring and maintenance is necessary to ensure the sensor's power supply for continuous operation over extended periods, e.g., days, weeks, months, or years.

[0007] Further state of the art can be found in the documents DE 10 2018 218 290 A1, US 2020 0 149 377 A1, WO 2020 159 950 A1, CN 1 08 230 650 A1 and US 2016 0 097665 A1.

[0008] Against this background, the invention aims to provide an improved sensor, for example a vibration sensor, that is less sensitive to the influence of disturbances, e.g., caused by turbulent media surrounding or flowing around the sensor (e.g., liquids, contents, gases, and the like), and whose measurement reliability is increased, which in turn provides improved sensor measurement accuracy. In addition, the invention should enable autonomous operation of the sensor, in particular energy-autonomous, independent operation over extended periods, in order to minimize maintenance and service interventions for the sensor. Furthermore, the sensor, e.g., the vibration sensor, should also operate reliably under operating conditions where high temperatures may occur, for example, 150 °C, 200 °C, or 300 °C and above.

[0009] This problem is solved by a sensor having the features of claim 1 and by a method having the features of claim 12. Further, particularly advantageous embodiments of the invention are disclosed in the respective dependent claims.

[0010] It should be noted that the features listed individually in the claims can be combined with one another in any technically meaningful way (even across category boundaries, for example between method and apparatus) and demonstrate further embodiments of the invention. The description further characterizes and specifies the invention, particularly in conjunction with the figures.

[0011] It should also be noted that the conjunction “and / or” used herein, which stands between two features and links them together, is always to be interpreted in such a way that in a first embodiment of the object according to the invention only the first feature may be present, in a second embodiment only the second feature may be present, and in a third embodiment both the first and the second feature may be present.

[0012] According to the invention, a sensor, which can be, for example, a vibration sensor without any limitation, has a measuring unit attached to a sensor housing that is at least partially surrounded by the medium for determining a process parameter, such as a fill level, limit level, density, or viscosity of a medium. In other words, when the sensor is used as intended, the sensor housing, or at least the measuring unit attached to the sensor housing, is located in such close proximity to the medium whose process state is to be determined that the medium can surround or flow around the sensor housing and possibly also the measuring unit, at least when a certain process state is reached. The sensor or the vibration unit can also be constantly surrounded by the medium during the intended use of the sensor.

[0013] According to the invention, at least one turbine wheel driving an electric generator (e.g., a dynamo) is rotatably mounted on the sensor housing about an axis of rotation. The turbine wheel is held on the sensor housing in such a way that it can be set into rotation by the medium surrounding the sensor housing, i.e., as soon as the medium at least partially surrounds the sensor housing, and the turbine wheel is attached at a distal end in the immediate vicinity of the measuring unit located at the distal end.

[0014] In other words, the medium surrounding the sensor, at least partially, is capable of generating an electric current by driving at least one turbine wheel. This current is caused by the movement of the medium relative to the sensor or sensor housing. The generator is driven by the turbine wheel. This current can, for example, be used as a signal to determine whether the sensor housing and / or the measuring unit is surrounded by a flowing or turbulent medium and can be used to validate the actual measurement signal obtained by the measuring unit.Particularly in applications where the medium can temporarily assume both turbulent and essentially static / steady-state conditions during measurement, for example, in a container where the medium is temporarily set in motion by an agitator, or in a pipeline where the medium flows intermittently and remains stationary, the measurement reliability of the sensor can be significantly improved. This is crucial because the measurement result would otherwise be distorted by disturbances / vibrations caused by a turbulent medium surrounding the sensor housing and / or the measuring unit. Specifically, the magnitude of the current generated by the generator, which correlates with the rotational speed of the turbine wheel, can also be used to determine the relative velocity of the medium with respect to the sensor or sensor housing, and thus the strength of the influence of the disturbance (vibration) caused by this current at the sensor.This information can be used in particular to improve measurement accuracy. For example, the measurement signal provided by the measuring unit can be filtered accordingly, taking into account the flow velocity of the medium, which is also detected, in order to remove or at least significantly reduce the proportion of interfering vibrations from the measurement signal.

[0015] Similarly, for example, an airflow generated by an agitator, which may be used to maintain movement / mixing of the medium (e.g., in a container), can cause rotation of at least one turbine wheel. This rotation, in combination with the measurement signal provided by the measuring unit, can be interpreted as an uncovering of the sensor housing and / or the measuring unit, thus preventing measurement errors and resulting misinterpretations. This evaluation can be performed, for example, by sensor electronics, which may be a component of the sensor.

[0016] Furthermore, a gyroscopic effect caused by the rotating turbine wheel can additionally dampen vibrations in the sensor housing holding the measuring unit (natural vibration, resonance frequency of the housing), which counteracts the excitation of disturbance vibrations by the turbulent medium, leading to a significant improvement in the measurement accuracy of the sensor.

[0017] Furthermore, the drive of the turbine wheel reveals, especially if the turbine wheel is located in close proximity to the measuring unit, that the sensor housing in the area of ​​the measuring unit or the measuring unit of the sensor is / are securely covered, although the sensor's measurement signal is actually uncertain or ambiguous if the medium is in motion relative to the sensor.

[0018] It is understood that the evaluations of the generator-generated current described herein can be performed, for example, by an electronic control unit (sensor electronics), such as a microprocessor, microcontroller, DSP, or similar device, possibly including an electronic storage unit like RAM, ROM, Flash, or the like. The electronic control unit can advantageously be integrated into the sensor housing, but is not limited to this. The control unit can also be located at a location spatially remote from the sensor, for example, in the form of a data processing / data analysis computer at a central data processing center, with the sensor transmitting its measurement data to the remote data processing unit either via a wired or wireless connection.

[0019] Furthermore, the current generated by the electric generator can also be used to power electrical components of the sensor itself, such as the measuring unit and / or any electronic control unit integrated into the sensor. If the self-generated current is not continuously available, the sensor can be equipped with a corresponding power buffer, for example, in the form of a rechargeable battery, a storage capacitor, supercapacitors, or similar devices. This enables energy-autonomous sensor operation, independent of any external power supply, over extended periods, such as several days, weeks, or even months. Maintenance and...

[0020] Service calls, for example to replace used batteries in the sensor, can be reduced or even completely avoided.

[0021] As mentioned above, preferred process variables to be determined by the sensor according to the invention can be a fill level, limit level, density, viscosity, or pressure of the medium. The sensor is then configured and arranged to determine a fill level, limit level, or pressure of a liquid or gaseous medium. The medium can be located in an (open or closed) container or pipe, in which the exact fill level of the medium, or merely the reaching of one or more predetermined limit levels in the container, or the container pressure is determined. The determination of a fill level, limit level, or pressure of a medium can also take place in a free (e.g., natural) environment, for example, the water level of a body of water (e.g., river, canal / sewage channel, and the like) or atmospheric pressure.

[0022] According to an advantageous embodiment of the invention, the sensor is a vibration sensor for the vibronic determination of the process variable, for example, a fill level, limit level, density, or viscosity of the medium. The vibration sensor comprises a mechanical vibration unit designed as the measuring unit and a drive unit housed in the sensor housing for exciting the vibration unit to vibrate and for detecting the vibration of the vibration unit. The vibration unit is designed and arranged in such a way as to be surrounded by the medium and to transmit the excited vibration to the medium. In other words, the sensor housing is located...At least the vibration unit attached to the sensor housing, when the vibration sensor is used as intended, is positioned in such close proximity to the medium whose process state is to be determined that the medium can surround or flow around the vibration unit, at least when a certain process state is reached. The vibration sensor or the vibration unit can also be constantly surrounded by the medium during the sensor's intended use. The turbine wheel is mounted on the sensor housing in such a way that it can be set in rotation by the medium that at least partially surrounds the vibration unit, i.e., as soon as the medium at least partially surrounds the vibration unit.

[0023] The electricity generated by the electric generator can be used to power electrical components of the vibration sensor, such as the drive and / or any electronic control unit that may be provided in the sensor.

[0024] As mentioned above, preferred process variables to be determined by the vibration sensor of the measuring device according to the invention can be a fill level, limit level, density, viscosity, or pressure of the medium. The vibration sensor is then configured and arranged to determine a fill level, a limit level, or a pressure of a liquid or gaseous medium. The medium can be located in an (open or closed) container or pipe, in which the exact fill level of the medium, or merely the reaching of one or more predetermined limit levels in the container, or the container pressure is determined. The determination of a fill level, limit level, or pressure of a medium can also take place in a free (e.g., natural) environment, for example, a water level (gauge) of a body of water (e.g., river, canal / sewage channel, and the like) or atmospheric pressure.

[0025] An advantageous embodiment of the invention provides that the axis of rotation of the turbine wheel is oriented essentially perpendicular to the main flow direction of the medium surrounding the sensor housing and / or the measuring unit or the vibration unit (in the case of a vibration sensor), as expected during sensor operation. This enables efficient drive of the turbine wheel by the flowing, turbulent medium. Furthermore, even relatively low flow velocities of the medium result in rotation of the turbine wheel, so that the detection of the medium flow occurs as early as possible and / or the power supply by the generator is optimized.

[0026] According to a further advantageous embodiment, the drive in the case of the vibration sensor is an inductive drive. This offers the particular advantage that the vibration sensor can be used reliably even at high ambient / operating temperatures, meaning it delivers reliable measurement results. These results are further significantly improved in combination with the turbine wheel for flow detection of the medium. For the purposes of the invention, high ambient / operating temperatures are understood to mean, in particular, temperatures above at least 150 °C, at least 200 °C, or at least 300 °C and higher.

[0027] It should be noted that the invention is not necessarily limited to inductive drive in the case of a vibration sensor. A piezoelectric drive, as is generally known, is also possible in principle.

[0028] Advantageously, in the case of the vibration sensor, the mechanical vibration unit can be designed in a further embodiment of the invention as a fork-type vibrator with at least two vibrating bodies projecting from the sensor housing.

[0029] According to another advantageous embodiment of the invention, the sensor housing is designed as an elongated sensor tube whose axial length is several times its diameter. Such an elongated sensor tube (extension tube) offers the advantage of being able to detect process conditions, for example, at a point in the container that is relatively far from a container wall. On the other hand, a long sensor tube can have the property of being easily excited to natural oscillations by the turbulent, flowing medium, so that the disclosed invention exhibits particularly advantageous effects with such a sensor design. In addition, the gyroscopic effect of the rotating turbine wheel can also provide effective vibration damping of the long sensor tube.

[0030] A further advantageous embodiment of the invention provides for several turbine wheels distributed along the axial length of the sensor housing, for example, at regular intervals. This further improves the vibration damping of the sensor housing or sensor tube due to the additive gyroscopic effects of the multiple turbine wheels. Furthermore, the turbine wheels arranged along the sensor housing enable even more precise level detection. Additionally, the overall energy yield can be further increased when driving multiple turbine wheels.

[0031] According to the invention, at least one turbine wheel is held at an end section of a free, distal end of the sensor housing. The distal (free) end of the sensor housing is understood to be a housing end that is immersible in or surrounded by the medium and that faces a proximal, fixed housing end of the sensor. At the fixed, proximal end, the sensor housing or the sensor can be attached, for example, to a container holding the medium, such as a tank, pipe, or the like. By arranging the turbine wheel at the free, distal end of the sensor housing, in particular an elongated sensor tube designed as a sensor housing, the gyroscopic effect of the rotating turbine wheel can produce particularly effective vibration damping of the sensor housing or sensor tube (large leverage effect with respect to the proximal, fixed end of the sensor housing).

[0032] A further embodiment of the invention provides that the axis of rotation of the at least one turbine wheel is aligned essentially parallel to the axial length of the sensor housing or sensor tube.

[0033] According to an alternative advantageous embodiment of the invention, the axis of rotation of the turbine wheel can be oriented essentially perpendicular to the axial length of the sensor housing or sensor tube.

[0034] In both cases, particularly efficient vibration damping is achieved through the gyroscopic effect of the turbine wheel. For example, the gyroscopic effect of the turbine wheel already has a vibration-damping effect on the sensor tube at low turbine speeds. Furthermore, according to the invention, the turbine wheel is attached to the distal end or an adjacent end section of the sensor housing or sensor tube, for example, in the immediate vicinity of the measuring unit (e.g., the vibration unit of a vibration sensor) located at the distal end, in order to achieve particularly effective vibration damping of the entire sensor housing or sensor tube by maximizing leverage with respect to the defined proximal end of the sensor housing or sensor tube.

[0035] According to a further advantageous embodiment of the invention, a rechargeable electronic energy storage device is provided in which the electrical energy generated by the generator can be stored. The energy storage device provides the electrical power supply to the sensor, for example, in particular to the measuring unit, the drive in the case of a vibration sensor, etc. Generally, the energy storage device can provide the electrical power supply to individual or all electronic components of the sensor, for example, any electronic control unit that may be present, as described above. The energy storage device is preferably designed as a rechargeable battery (accumulator), but this is not strictly limited to the above. Storage capacitors, supercapacitors, and the like are also conceivable for energy storage. The energy storage device is preferably housed within the sensor casing.

[0036] The sensor according to the invention is particularly preferably a level sensor or fill level sensor, but is not necessarily limited to this. Other application areas of the sensor mentioned herein are also possible.

[0037] According to a further aspect of the invention, a method for determining a process variable, for example a fill level, limit level, density, or viscosity, of a medium is disclosed using a sensor, wherein the sensor is configured according to one of the embodiments described herein. In this method, the process variable is determined by means of the measuring unit, which, in the case of a vibration sensor, can be configured, for example, as a vibration unit. Movement of the medium, which at least partially surrounds the sensor housing, relative to the sensor housing is detected by means of the at least one turbine wheel rotatably mounted on the sensor housing and used to evaluate / validate the determined process variable, as already explained above.

[0038] Therefore, with regard to process-related definitions as well as the effects and advantages of process-related features, reference is made in full to the disclosure of analogous definitions, effects, and advantages of the vibration sensor according to the invention. Accordingly, disclosures herein relating to the sensor according to the invention may be used analogously to define the process according to the invention, unless this is expressly excluded. Likewise, disclosures herein relating to the process according to the invention may be used analogously to define the sensor according to the invention. In this respect, a repetition of explanations of analogous features, their effects, and advantages of the sensor according to the invention and of the process according to the invention can be omitted in favor of a more concise description, without such omissions being to be interpreted as a limitation.

[0039] According to an advantageous embodiment of the invention, the electrical energy generated by the rotation of at least one turbine wheel by means of the generator is stored in an energy storage device of the sensor, for example, a battery, storage capacitor, and the like, and used by the sensor as an electrical power supply for its operation. Preferably, all electronic components of the sensor are powered from the electrical energy storage device.

[0040] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, which are not to be understood as limiting and are explained in more detail below with reference to the drawing. This drawing schematically shows: Fig. 1 a side view of an embodiment of a sensor according to the invention, Fig. 2 a first application example of the sensor from Fig. 1 and Fig. 3 a second application example of the vibration sensor from Fig. 1.

[0041] In the different figures, parts that are equivalent in function are always provided with the same reference symbols, so that they are usually only described once.

[0042] Fig. Figure 1 schematically depicts a side view of an embodiment of a sensor 1, designed without any limitations as a vibration sensor, e.g., in the form of a level sensor or fill level sensor, according to the invention. The sensor or vibration sensor 1 serves to determine a process variable, in particular a fill level, limit level, density, or viscosity of a liquid or gaseous medium 2, as described in the Fig. 2 and Fig. 3 can be seen, for example, in a (closed) container 3 or a pipeline 4.

[0043] The in Fig. The vibration sensor 1 shown as an example has a measuring unit 6 attached to a sensor housing 5, which in this case is designed as an elongated sensor tube, but is not necessarily limited to this form. The measuring unit 6 is designed as a mechanical vibration unit. As can be seen, the vibration unit 6 in the vibration sensor 1 is designed as a fork-type oscillator with at least two vibrating elements 7 projecting from the sensor housing 5. The vibration unit 6 is attached to a distal (free) end 8 of the sensor tube 5, but is not necessarily limited to this position. A proximal end 9 is located at the opposite end of the sensor tube 5. As shown in the Fig. 2 and Fig. As can be clearly seen in Figure 3, the vibration sensor 1 is firmly attached to the container 3 or the pipeline 4 at its proximal end 9.

[0044] Furthermore, the in Fig. The vibration sensor 1 shown in Figure 1 provides a drive 10 (schematically indicated) housed in the sensor housing 5, in this case an inductive drive, but not necessarily limited to this, for exciting the vibration unit 6 to vibrate and for detecting the vibration of the vibration unit 6. The vibration unit 6 is designed and arranged in such a way that it can be at least partially surrounded by the medium 2 (see Figure 1). Fig. 2 and Fig. 3) and transmit the excited vibration to the medium 2.

[0045] Fig. Figure 1 further shows that a turbine wheel 12, which drives an electric generator 11 (dynamo), is rotatably mounted on the sensor housing 5 about a rotational axis 13. During the intended operation of the vibration sensor 1, the turbine wheel 12 is set into rotation by the medium 2 surrounding the vibration unit 6 when this medium moves relative to the vibration sensor 1, for example, when it flows past it and / or is in a turbulent state.

[0046] As already mentioned, the sensor housing 5 of the in Fig. In the embodiment of the vibration sensor 1 shown in Figure 1, the sensor tube is designed as an elongated tube whose axial length L is a multiple of its diameter D. The turbine wheel 12 is held at an end section of the free, distal end 8 of the sensor tube 5, in this case, in particular, in close proximity to the vibration unit 6.

[0047] Furthermore, it can be seen that the axis of rotation 13 of the turbine wheel 12 in the vibration sensor 1 is essentially aligned parallel to a longitudinal axis 14 of the sensor tube 6. A possible rotation of the turbine wheel 12 is in Fig. 1 indicated by a circular arrow. It should be noted that the axis of rotation of the turbine wheel 12, with appropriate design of the turbine wheel 12, is oriented with respect to an expected main flow direction 18 (cf. Fig. 2 and Fig. 3) the medium 2 can also be arranged perpendicular to the longitudinal axis L of the sensor housing 5, as is the case in Fig. 1 is to be indicated by example by the axis of rotation 13'.

[0048] Furthermore, in the Fig. The vibration sensor 1 shown in Figure 1 incorporates a rechargeable electronic energy storage device 15, which in this case is designed as an accumulator, although this is not necessarily the only possible configuration. The electrical energy generated by the generator 11 is stored in the energy storage device 15. Furthermore, the vibration sensor 1 includes an electronic control unit 16, which can perform the functions described in the general section of this description. In the vibration sensor 1 shown, the energy storage device 15 provides the electrical power supply for both the drive 10 and the electronic control unit 16.

[0049] Fig. Figure 2 presents a first application example of the vibration sensor 1. Fig. 1 dar.

[0050] In Fig. Figure 2 shows how the vibration sensor 1 is attached to the container 3 with its proximal end 9, and how the sensor housing or sensor tube 5 protrudes into the interior of the container, which holds the medium 2. The section circled with a dashed line in Fig. The vibration sensor 1 shown in 2 essentially corresponds to the one in Fig. 1 sensor section shown.

[0051] In the Fig. In the container 3 shown in Figure 2, an agitator 17 is arranged, which can set the medium 2 in motion. The agitator 17 is switched on at predetermined intervals and then switched off again. The movement of the medium 2 when the agitator 17 is switched on is reliably detected by the vibration sensor 1, as explained in detail in the general section of this description, and is used to validate the measurement signals acquired by the vibration sensor 1, i.e., by the measuring unit 6 or, in this case, the vibration unit 6. Furthermore, the electrical energy required for the operation of the vibration sensor 1 is generated from the movement of the medium 2 by means of the generator 11. This energy can be stored in the energy storage device 15 to enable the sensor to continue its intended operation when the agitator 17 is switched off.A possible main flow direction 18 of the medium 2 (at least in spatial proximity to the turbine wheel 12 of the sensor 1) in the container 3 is in . Fig. Figure 2 is shown as an example. The axis of rotation 13 of the turbine wheel 12 is essentially oriented perpendicular to the main flow direction 18. In Fig. 2 also indicates that the sensor 1 can have several turbine wheels 12, for example those in Fig. The two indicated turbine wheels 12', 12'', 12''' can be arranged distributed along the axial length L of the sensor housing 5. The arrangement can be at equal relative distances between the turbine wheels 12, 12', 12'', 12''' over the entire length L, but is not necessarily limited to this.

[0052] Fig. Figure 3 presents another application example in which the sensor 1, in this case, but without any limitation here, the vibration sensor 1, is made of Fig. 1 is used. It can be seen that the vibration sensor 1 is attached to the pipe 4 at its proximal end 9. The distal end 8 of the sensor housing or sensor tube 5 projects into the interior of the pipe 4, in which the medium 2 is contained. In Fig. 3 is the (possibly temporary) main flow direction 18 of the medium 2 within the pipeline 4. Furthermore, in Fig. 3 to recognize that the axis of rotation 13 of the turbine wheel 12 is oriented essentially perpendicular to the main flow direction 18 of the medium 2 surrounding the vibration unit 6.

[0053] The sensor and method disclosed herein are not limited to the embodiments disclosed herein, but also include further embodiments with equivalent effects that result from technically useful combinations of the features of the sensor and the method described herein. In particular, the features and combinations of features mentioned above in the general description and the description of the figures and / or shown in the figures alone can be used not only in the combinations explicitly specified herein, but also in other combinations or individually, without departing from the scope of the present invention.

[0054] In a preferred embodiment, the sensor according to the invention is used for measuring the level, limit level, viscosity or pressure of a liquid or gaseous medium, wherein in a particularly preferred embodiment the sensor is designed as a vibration sensor with a vibration unit as the measuring unit. Reference symbol list 1 sensor / vibration sensor 2 Medium 3 containers 4 Pipeline 5 Sensor housing / sensor tube 6 Measuring unit / Vibration unit 7 vibrating bodies 8 Distal (free) end 9 Proximal end 10 Drive 11 Generator 12 Turbine wheel 12' turbine wheel 12'' turbine wheel 12''' turbine wheel 13. Axis of rotation 13' Alternative axis of rotation 14 Longitudinal axis of 5 15 Energy storage 16 Electronic control unit 17 Agitator 18 Flow direction from 2 D diameter of 5 L Length of 5

Claims

[1] Sensor (1) for determining a process variable, in particular a level, limit level, density or viscosity, of a medium (2), comprising a measuring unit (6) attached to a sensor housing (5) which is at least partially surrounded by the medium (2) for determining the process variable of the medium (2), characterized by , that at least one turbine wheel (12, 12', 12'', 12''') driving an electric generator (11) is rotatably mounted on the sensor housing (5) about an axis of rotation (13, 13') such that the at least one turbine wheel (12, 12', 12'', 12''') can be set into rotation by the medium (2) surrounding the sensor housing (5), and the turbine wheel is attached to a distal end of the sensor housing in the immediate vicinity of the measuring unit arranged at the distal end, wherein the distal end of the sensor housing is to be understood as a housing end that can be surrounded by the medium and is opposite a proximal, fixed housing end of the sensor. [2] Sensor (1) according to claim 1, characterized by , that the sensor (1) is a vibration sensor with a mechanical vibration unit designed as the measuring unit (6) and a drive (10) received in the sensor housing (5) for exciting the vibration unit (6) to vibrate and for detecting a vibration of the vibration unit (6), wherein the vibration unit (6) is designed and arranged in such a way as to be able to be at least partially surrounded by the medium (2) and to transmit the excited vibration to the medium (2). [3] Sensor (1) according to claim 2, characterized by , that the axis of rotation (13) of the at least one turbine wheel (12, 12', 12'', 12''') is oriented substantially perpendicular to a main flow direction (18) of the medium (2) surrounding the vibration unit (6). [4] Sensor (1) according to claim 2, characterized by , that the drive (10) is an inductive drive. [5] Sensor (1) according to claim 2 or 4, characterized by, that the mechanical vibration unit (6) is designed as a fork-type vibrator with at least two vibrating bodies (7) extending from the sensor housing (5). [6] Sensor (1) according to any one of the preceding claims, characterized by , that the sensor housing (5) is designed as an elongated sensor tube whose axial length (L) is a multiple of its diameter (D). [7] Sensor (1) according to the preceding claim, characterized by , that several turbine wheels (12, 12', 12'', 12''') are provided, which are arranged distributed along the axial length (L) of the sensor housing (5). [8] Sensor (1) according to claim 6 or 7, characterized by , that the axis of rotation (13) of the at least one turbine wheel (12, 12', 12'', 12''') is oriented essentially parallel to the axial length (L) of the sensor tube (5). [9] Sensor (1) according to claim 6 or 7, characterized by, that the axis of rotation (13') of the at least one turbine wheel (12) is oriented substantially perpendicular to the axial length (L) of the sensor tube (5). [10] Sensor (1) according to any one of the preceding claims, characterized by , that a rechargeable electronic energy storage device (15) is provided in which the electrical energy generated by the generator (11) can be stored, wherein the energy storage device (15) provides the electrical energy supply to the sensor (1). [11] Sensor (1) according to any one of the preceding claims, characterized by , that the sensor (1) is a level sensor or fill level sensor. [12] Method for determining a process variable, in particular a level, limit level, density or viscosity, of a medium (2), by means of a sensor (1) for determining a process variable, in particular a level, limit level, density or viscosity, of a medium (2), comprising a measuring unit (6) attached to a sensor housing (5) which is at least partially surrounded by the medium (2) for determining the process variable of the medium (2), characterized by, that at least one turbine wheel (12, 12', 12'', 12''') driving an electric generator (11) is rotatably mounted on the sensor housing (5) about an axis of rotation (13, 13') such that the at least one turbine wheel (12, 12', 12'', 12''') can be set into rotation by the medium (2) surrounding the sensor housing (5), wherein the process variable is determined by means of the measuring unit (6) and a movement of the medium (2) at least partially surrounding the sensor housing (5) of the vibration sensor (1) relative to the sensor housing (5) is detected by means of the at least one rotatable turbine wheel (12, 12', 12'', 12''') and is used to evaluate the determined process variable. [13] Method according to the preceding claim, characterized by, that the electrical energy generated from the rotation of at least one turbine wheel (12, 12', 12'', 12''') by means of the generator (11) is stored in an energy storage device (15) of the sensor (1) and is used by the sensor (1) as an electrical energy supply for its operation.

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