Method and device for detecting contamination of a MEMS sensor element

Abstract

The invention relates to a method for detecting contamination of a micro-electromechanical sensor element, the method comprising the following steps: outputting a heating control signal for controlling a heating device in order to heat the sensor element; receiving a measurement signal, the measurement signal representing a physical variable measured by means of the heated sensor element; determining based on the measured physical variable whether the sensor element is contaminated or free of contamination; outputting a result signal, the result signal representing a result, the result indicating whether the sensor element is contaminated or free of contamination. The invention also relates to a device.

Description

Technical Field

[0001] The invention relates to a method for detecting contamination of a micro-electromechanical sensor element. The invention also relates to a device. Background Art

[0002] There are media-stable and / or waterproof MEMS pressure sensors on the market, which achieve this property by means of a gel coating of the sensing element or the entire component. These pressure sensors are used, for example, in mobile phones or smart watches to measure air pressure and are therefore exposed to very different environmental influences and media in liquid or solid form.

[0003] The protective gel is in direct contact with the sensing element on the one hand and with the environment on the other hand. When the sensor (more precisely, the gel surface) comes into contact with water, other liquids or generally with dirt, this can lead to an influence on the output signal of the pressure sensor. Changes in the sensor signal can be achieved by chemical, electrical or mechanical interactions of the gel with the dirt. It is not important here whether the sensor signal is directly influenced by the dirt or whether there are secondary interactions due to changes in the gel properties. The accuracy of the sensor can be worse than desired.

[0004] Because these sensors are configured as terminal devices specifically for waterproofing, they are often contaminated by water. After the device is removed from the water, water often remains on the sensor.

[0005] Contamination can cause the sensor's behavior to no longer correspond to the specification or the sensor to become completely unusable.

[0006] There is therefore a need to detect contamination of a micro-electromechanical sensor element.

[0007] The published patent application DE 10 2008 002 579 A1 discloses a micro-electromechanical sensor element.

[0008] The published patent application DE 10 2005 029 841 A1 discloses a micromechanical device having an integrated heating device. Summary of the invention

[0009] The object of the present invention is to provide a concept for the efficient detection of contamination of a micro-electromechanical sensor element.

[0010] This object is achieved by means of the present invention. Advantageous embodiments of the present invention emerge from the preferred embodiments.

[0011] According to a first aspect, a method for detecting contamination of a micro-electromechanical sensor element is provided, the method comprising the following steps:

[0012] - outputting a heating control signal for controlling the heating device so as to heat the sensor element;

[0013] - receiving a measurement signal, which is representative of a physical variable measured by means of the heated sensor element;

[0014] - based on the measured physical variable, determining whether the sensor element is contaminated or free of contamination;

[0015] - outputting a result signal, which represents a result indicating whether the sensor element is contaminated or free of contamination.

[0016] According to a second aspect, a device for detecting contamination of a micro-electromechanical sensor element is provided, the device comprising:

[0017] - micro-electromechanical sensor elements;

[0018] a heating device, which is arranged to heat the micro-electromechanical sensor element; and

[0019] - signal processing means,

[0020] The signal processing device has an output end, which is configured to output a heating control signal for controlling the heating device so as to heat the sensor element.

[0021] The signal processing device has an input which is configured to receive a measurement signal which represents a physical variable measured by means of the heated sensor element.

[0022] The signal processing device has a processor which is configured to determine, based on the measured physical variable, whether the sensor element is contaminated or free of contamination,

[0023] Therein, the output end is configured to output a result signal, which represents a result indicating whether the sensor element is contaminated or free of contamination.

[0024] The invention is based on and includes the finding that the aforementioned object can be achieved in that the sensor element is heated or heated, wherein the sensor element measures the physical variable in the heated or heated state.

[0025] Based on the measured physical variable, it is determined whether the sensor element is contaminated or free of contamination, and a corresponding result is output.

[0026] If the sensor element is contaminated, this will have an influence on the measuring process, ie the measurement of the physical variable.

[0027] Furthermore, the thermal properties, in particular the heat transfer properties, of the sensor element may change, in particular if the sensor element is contaminated.

[0028] The thermodynamic surrounding conditions of the sensor element generally have an influence on the measurement of the physical variable, that is, the measured physical variable is particularly dependent on the thermodynamic surrounding conditions.

[0029] Thus, by heating the sensor element, the thermodynamic ambient conditions of the sensor element can be effectively influenced, which are then reflected in the measured physical variable.

[0030] Based on the measured physical variable, it can therefore be efficiently determined whether the sensor element is contaminated or free of contamination.

[0031] In particular, the technical advantage is achieved thereby that a concept for efficiently detecting contamination of a microelectromechanical sensor element is provided.

[0032] For the term “microelectromechanical” in particular the abbreviation MEMS may be used.

[0033] For example, the sensor element is an element selected from the following sensor element group: pressure sensor, temperature sensor, gas sensor, voltage sensor, current sensor, resistance sensor, video sensor, lidar sensor, ultrasonic sensor, magnetic field sensor, infrared sensor and radar sensor.

[0034] According to one embodiment, it is provided that the sensor element is protected by means of a protective layer. For example, the sensor element is covered by means of the protective layer. Thus, according to one embodiment, the sensor element is provided with a protective layer.

[0035] According to one embodiment, the protective layer comprises a gel.

[0036] Thus, dirt can be deposited especially on the gel.

[0037] The expression “the sensor element is free of contamination” includes in particular: the gel is free of contamination.

[0038] The expression “the sensor element is contaminated” includes in particular that the gel is contaminated.

[0039] If the sensor element is a pressure sensor, the measured physical variable is the pressure.

[0040] If the sensor element is a temperature sensor, the measured physical variable is the temperature.

[0041] According to one embodiment, the contaminants include fluids and / or dust and / or solids and / or biofilms.

[0042] According to one embodiment, the fluid comprises water and / or one or more other liquids.

[0043] According to one specific embodiment, it is provided that a temperature signal is received which represents the sensor element temperature and / or the ambient temperature, wherein it is determined based on the temperature signal whether the sensor element is contaminated or free of contamination.

[0044] This achieves, for example, the technical advantage that it is possible to efficiently determine whether the sensor element is contaminated or free of contamination.

[0045] Since the sensor element temperature and / or the ambient temperature are known, thermodynamic ambient conditions or thermal properties, in particular heat transfer properties, of the sensor element can be efficiently ascertained.

[0046] Thermodynamic ambient conditions or heat transfer properties have an influence on the measured physical variable, so that it is possible to effectively determine whether the sensor element is contaminated or free of contamination.

[0047] According to one specific embodiment, it is provided that a reference signal is received which represents a reference physical variable, wherein it is determined based on the reference physical variable whether the sensor element is contaminated or free of contamination.

[0048] This achieves, for example, the technical advantage that it is possible to efficiently determine whether the sensor element is contaminated or free of contamination.

[0049] For example, a reference physical variable is measured under known conditions, in particular known thermodynamic ambient conditions, by means of an electromechanical sensor element, in particular by means of a microelectromechanical sensor element. In particular, the sensor element is free of contamination when measuring the reference physical variable. That is, the sensor element is free of contamination when measuring the reference physical variable.

[0050] This means, in particular, that in the event of a deviation of the measured physical variable from the reference physical variable, in particular a deviation within a predetermined tolerance range, it can be determined that the sensor element is contaminated.

[0051] If the deviation lies within a predetermined tolerance range, for example, it is determined that the sensor element is free of contamination, otherwise it is determined that the sensor element is contaminated.

[0052] This means in particular that, according to one specific embodiment, it is provided that a deviation of the measured physical variable from a reference physical variable is ascertained, wherein it is ascertained based on the ascertained deviation whether the sensor element is contaminated or free of contamination.

[0053] The reference physical variable and the measured physical variable have the same physical units.

[0054] In one specific embodiment, it is provided that the measured physical variable comprises a time profile of the physical variable.

[0055] In one specific embodiment, it is provided that the reference physical variable comprises a time profile of the reference physical variable.

[0056] According to one specific embodiment, it is provided that when it is determined that the sensor element has contamination, it is determined what type of contamination this is, wherein the result additionally indicates the type of contamination.

[0057] This achieves, for example, the technical advantage that suitable countermeasures can be effectively taken depending on the type of contamination.

[0058] If the impurities include a fluid, in particular water, a drying process can be suggested or initiated or carried out, for example.

[0059] If the dirt comprises dust, for example, a cleaning process can be suggested or initiated or carried out, for example.

[0060] According to one specific embodiment, the type of contamination is ascertained based on the measured physical variable and / or based on the temperature signal and / or based on the reference physical variable.

[0061] According to one specific embodiment, it is provided that a water contact signal is received which represents a detected contact of the surroundings of the sensor element with water, wherein determining “which type of contamination is” includes determining that “the type of contamination includes water”.

[0062] This achieves, for example, the technical advantage that the type of contamination can be efficiently ascertained.

[0063] According to one specific embodiment, it is provided that, when contamination of the sensor element is detected, a control signal is output for controlling the contamination removal process.

[0064] This achieves, for example, the following technical advantage: dirt can be removed effectively.

[0065] According to one specific embodiment, it is provided that the control signal is output as a function of the ascertained type of contamination.

[0066] This achieves, for example, the following technical advantage: dirt can be removed effectively.

[0067] According to one embodiment, if the contaminant includes water and / or fluid and / or biofilm, the control signal includes a drying heating control signal for controlling a heating device so as to dry the sensor element by heating, and / or, if the contaminant includes dust and / or solids and / or biofilm, the control signal includes a cleaning control signal for controlling a cleaning device so as to clean the sensor element.

[0068] This achieves, for example, the following technical advantage: dirt can be removed effectively.

[0069] According to one embodiment, the sensor element is included in an appliance, which includes a water identification device, which is configured to identify contact between the appliance and water and output a water contact signal when contact between the appliance and water is identified, wherein the type of contaminant is determined based on whether the water contact signal has been received.

[0070] This achieves, for example, the technical advantage that the type of contamination can be efficiently ascertained.

[0071] For example, if no water contact signal is received, it is determined, for example, that the contamination does not include a fluid, in particular no water.

[0072] For example, if a water contact signal is received, it is determined that the contamination comprises a fluid, in particular water.

[0073] According to one embodiment, the sensor element is comprised by the device.

[0074] According to one embodiment, the appliance comprises water identification means.

[0075] According to one embodiment, the water recognition device is configured to recognize contact between the appliance and water and output a water contact signal when contact between the appliance and water is recognized.

[0076] According to one embodiment, the appliance comprises charging electronics.

[0077] According to one embodiment, the device is an element selected from the following group of devices: terminal equipment, in particular a mobile phone, a smart watch, a computer, a laptop, a tablet computer, a satellite navigation device.

[0078] According to one embodiment, it is provided that the sensor element is arranged within the housing.

[0079] According to one embodiment, the device comprises a housing.

[0080] According to one embodiment, it is provided that the heating device comprises one or more heating elements.

[0081] According to one embodiment, it is provided that the sensor element has a heating element.

[0082] According to one embodiment, it is provided that the heating element is integrated in the sensor element.

[0083] According to one embodiment, it is provided that a heating element is arranged on an outer surface of the sensor element.

[0084] According to one embodiment, it is provided that the housing comprises a heating element.

[0085] According to one embodiment, it is provided that the heating element is integrated in the housing.

[0086] According to one embodiment, a heating element is provided on the surface of the housing.

[0087] According to one embodiment, it is provided that a heating element is arranged on a surface of the housing.

[0088] According to one embodiment, it is provided that the sensor element is arranged on a printed circuit board.

[0089] According to one embodiment, it is provided that the circuit board comprises a heating element.

[0090] According to one embodiment, it is provided that the sensor element is arranged on a substrate or a carrier.

[0091] According to one embodiment, it is provided that the substrate or the carrier comprises a heating element.

[0092] If the singular is used for the heating element, it should always be read as including the plural and vice versa.

[0093] According to one embodiment, the sensor element is included in an appliance, which includes a water identification device, which is configured to identify contact between the appliance and water and output a water contact signal when contact between the appliance and water is identified, wherein the input end is configured to receive the water contact signal, wherein the processor is configured to determine, based on "whether the water contact signal has been received": what type of contaminant is.

[0094] One embodiment comprises a dirt removal device which is configured to carry out a dirt removal process, wherein the output is configured to output a control signal for controlling the dirt removal device in order to carry out the dirt removal process.

[0095] According to one embodiment, it is provided that the dirt removal device comprises one or more of the following: a heating device, a piezoelectric element for applying vibrations to the sensor element.

[0096] One embodiment comprises a memory in which a reference physical variable is stored, wherein the reference physical variable and the measured physical variable have the same physical unit, wherein an input terminal is configured to receive a reference signal representing the reference physical variable from the memory, wherein a processor is configured to determine based on the reference physical variable whether the sensor element is contaminated or free of contamination, wherein the processor is configured to determine a deviation of the measured physical variable from the reference physical variable, wherein the processor is configured to determine based on the determined deviation whether the sensor element is contaminated or free of contamination.

[0097] The advantages described in conjunction with the method apply analogously to corresponding embodiments of the device and vice versa.

[0098] The expression "or" means "either."

[0099] The expression "or" means "and / or".

[0100] According to one embodiment it is provided that the method according to the first aspect is a computer-implemented method.

[0101] According to one specific embodiment, it is provided that the method according to the first aspect is carried out or executed by means of the device according to the second aspect.

[0102] Analogously, device features follow from corresponding method features, and vice versa. This means, in particular, that the technical functionality of the device follows analogously from the corresponding technical functionality of the method, and vice versa.

[0103] In one embodiment, it is provided that the device according to the second aspect is configured to carry out all steps of the method according to the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0104] An exemplary embodiment of the present invention is shown in the drawings and explained in detail in the following description.

[0105] Figure 1 Flow chart of a method for detecting contamination of a micro-electro-mechanical sensor element,

[0106] Figure 2 equipment,

[0107] Figure 3-6 MEMS sensor elements, and

[0108] Figure 7 Graph.

[0109] In the following, the same reference numerals may be used for the same features. DETAILED DESCRIPTION

[0110] Figure 1 A flow chart of a method for detecting contamination of a micro-electromechanical sensor element is shown, the method comprising the following steps:

[0111] - output 101 a heating control signal for controlling a heating device in order to heat the sensor element;

[0112] - receiving 103 a measurement signal, which is representative of a physical variable measured by means of the heated sensor element;

[0113] - based on the measured physical variable, determining 105 whether the sensor element is contaminated or free of contamination;

[0114] - outputting 107 a result signal, which represents a result indicating whether the sensor element is contaminated or free of contamination.

[0115] In one embodiment, the method according to the first aspect comprises measuring a physical parameter, in particular measuring a curve of a change of the physical parameter over time.

[0116] Figure 2 A device 201 for detecting contamination 601 , 701 of a micro-electromechanical sensor element 203 is shown, the device comprising:

[0117] - micro-electromechanical sensor element 203;

[0118] a heating device 205 arranged to heat the micro-electromechanical sensor element 203; and

[0119] - signal processing means 207,

[0120] The signal processing device 207 has an output terminal 209, which is configured to output a heating control signal for controlling the heating device 205 so as to heat the sensor element 203.

[0121] The signal processing device 207 has an input 211 which is provided for receiving measurement signals which represent physical variables measured by means of the heated sensor element 203.

[0122] The signal processing device 207 has a processor 213 which is configured to determine, based on the measured physical variable, whether the sensor element 203 has contamination 601 , 701 or is free of contamination 601 , 701 ,

[0123] Therein, the output end 209 is configured to output a result signal, which represents a result indicating whether the sensor element 203 has contamination 601 , 701 or is free of contamination 601 , 701 .

[0124] Figure 3 Shown is a micro-electromechanical sensor element 501. The sensor element 501 is, for example, a pressure sensor.

[0125] The sensor element 501 is arranged on a bottom 502 of a housing 503 .

[0126] according to Figure 3 View and according to Figures 4 to 6 The views are cross-sectional views.

[0127] Two side walls of the housing 503 that are opposite to each other are denoted by reference numerals 505 and 507 .

[0128] Thus, a cavity 509 is formed in housing 503 , in which cavity the sensor element 501 is arranged.

[0129] The cavity 509 is partially filled with a protective layer 511 , which may comprise a gel, for example.

[0130] In this case, it is provided that protective layer 511 completely covers sensor element 501 .

[0131] exist Figure 3 In the illustration shown in , sensor element 501 is free of contamination as long as no contamination has formed on protective layer 511 .

[0132] Figure 4 Sensor element 501 is shown having a protective layer 511 , wherein water 601 is arranged on protective layer 511 .

[0133] In this context, sensor element 501 has contamination, in the present case water.

[0134] Figure 5 Sensor element 501 is shown including a protective layer 511 , wherein dust 701 has accumulated on protective layer 511 .

[0135] In this respect, sensor element 501 has contamination, in the present case dust 701 .

[0136] Apart from Figure 3 In addition to the diagram shown in Figure 6 Also shown is a heating device 800 comprising a plurality of heating elements.

[0137] The first heating element 801 is arranged on the inner surface of the left side wall 505 (with respect to the paper surface) of the housing 503 .

[0138] The second heating element 803 is arranged opposite to each other on the inner surface of the right housing side wall 507 .

[0139] The third heating element 805 is arranged between the sensor element 501 and the bottom 502 of the housing 503 .

[0140] Fourth heating element 807 is arranged on sensor element 501 , namely on the side of sensor element 501 facing away from base 502 .

[0141] Furthermore, a fifth heating element 809 is arranged on the underside of the housing 503. The underside 809 is the side of the housing 503 facing away from the base 502.

[0142] Figure 7 A graph 901 is shown.

[0143] Graph 901 includes an x-axis 903 and a y-axis 905 .

[0144] The x-axis 903 represents time in arbitrary units.

[0145] The y-axis 905 represents the physical quantity measured by the sensor element 501 in arbitrary units.

[0146] For example, if the sensor element 501 is a pressure sensor, the measured physical variable corresponds to the pressure.

[0147] Three curves are plotted in the graph 901 : a first curve 907 , a second curve 909 , and a third curve 911 .

[0148] Three curves 907 , 909 , 911 show the time response characteristics of the pressure signal of sensor element 501 corresponding to the measured pressure.

[0149] This time response characteristic is dependent, in particular, on the thermodynamic ambient conditions and / or on the heat transfer properties of sensor element 501 .

[0150] This means that the time response characteristics change when the ambient temperature varies.

[0151] Thus, a first curve 907 is recorded at a first temperature. A second curve 909 is recorded at a second temperature. A third curve 911 is recorded at a third temperature. These temperatures represent the ambient temperature of the sensor element 501 .

[0152] Here, the first temperature is greater than the second temperature, and the second temperature is greater than the third temperature.

[0153] On the x-axis 903 , a first time constant of the first curve 907 is plotted with reference numeral 913 , and a second time constant 915 of the second curve 909 and a third time constant 917 of the third curve 911 are plotted.

[0154] A first amplitude 919 of the first curve 907, a second amplitude 921 of the second curve 909, and a third amplitude 923 of the third curve 911 are plotted on the y-axis 905. The three amplitudes 919, 921, and 923 are defined relative to an offset 925.

[0155] Due to the thermal dependence of the time response characteristics, the three time constants are different and the three amplitudes are different.

[0156] However, if the sensor element, in this case in particular protective layer 511 , is provided with dirt, the temporal response characteristic also changes.

[0157] If the time response behavior in the clean state, ie when the sensor element is free of contamination, is therefore known, it is possible to determine by comparing the pressure measurement with these curves 907 , 909 , 911 whether sensor element 501 is free of contamination or has contamination.

[0158] The concept described here is also based on the fact that, knowing the heat transfer properties of the sensor element when it is internally heated, dirt, in particular water, can be detected on the sensor element, in particular on the surface of the protective layer, in particular on the surface of the gel, by using the heat conduction changed by the dirt to detect the presence of such dirt, in particular the presence of water. For this purpose, it is provided, for example, that a heating device integrated in the sensor element or a heating device present adjacent to the sensor element is used in order to heat the sensor element and / or its surroundings above the current temperature of the sensor element within a limited time.

[0159] For example, the sensor element temperature is measured simultaneously and in particular the physical variable measured by means of the heated sensor element, such as pressure, is measured. In this case, the time response characteristic of the sensor element signal, in particular the pressure signal, in particular the time response characteristic characterized by time constant and amplitude, is particularly dependent on the thermodynamic ambient conditions.

[0160] As long as the sensor element, in particular the protective layer, in particular the gel surface, is free of dirt, i.e., for example, clean and dry, the thermodynamic surroundings and the response characteristics associated therewith are always the same. In this case, the presence of water, in general, of dirt, results in an additional heat capacity and an additional transition thermal resistance compared to the clean and dry initial state. This causes a change in the time response characteristic previously measured and used as a reference in the thermal network. Therefore, the presence of water, in general, of dirt, can be inferred in an advantageous manner from the difference between the reference measurement in the clean and dry state and the subsequent measurement.

[0161] For example, it is provided that cleaning and / or drying is triggered based on a differentiation between different types of soiling.

[0162] The thermodynamic properties of different impurities, in particular different liquids, are in some cases very different, so that in particular by quantifying the thermal response properties it is possible to distinguish between different occupancy of the sensor element. For example, if the observed signature (measured physical variable) corresponds to a typical signature (reference physical variable) for liquids, a drying step can be initiated. If the signature is identical to non-liquid impurities, for example, a cleaning step can be initiated.

[0163] In addition, different contaminants can be distinguished or classified with the help of other measured variables. For example, many waterproof end devices have a separate detection device for contact with water, for example to protect charging electronics. Such a separate detection device is the aforementioned separate water detection device. If contamination of the sensor element is detected together with the additional water contamination detected by the separate water detection device, it is possible that there is water on the sensor element and drying is therefore arranged. If there is no such additional signal, i.e. a water contact signal, it is more likely that other types of contaminants are present and, for example, cleaning can be required.

Claims

1. A method for detecting contamination (601, 701) of a micro-electromechanical sensor element (203, 501), the method The following steps are involved: - outputting (101) a heating control signal for controlling a heating device (205) so as to heat the sensor element (203, 501); - receiving (103) a measurement signal, which represents a physical variable measured by means of the heated sensor element (203, 501); - based on the measured physical variable, determining (105) whether the sensor element (203, 501) has dirt (601, 701) or is free of dirt (601, 701); - outputting (107) a result signal, said result signal representing a result indicating whether said sensor element (203, 501) has dirt (601, 701) or is free of dirt (601, 701), A reference signal is received, which represents a reference physical variable, wherein the reference physical variable and the measured physical variable have the same physical unit, wherein it is determined based on the reference physical variable whether the sensor element (203, 501) has dirt (601, 701) or is free of dirt (601, 701), Therein, a deviation of the measured physical variable from the reference physical variable is ascertained, wherein it is ascertained based on the ascertained deviation whether the sensor element (203, 501) has contamination (601, 701) or is free of contamination (601, 701).

2. The method according to claim 1, in, A temperature signal is received, which represents a sensor element temperature of the sensor element (203, 501) and / or an ambient temperature, wherein it is determined based on the temperature signal whether the sensor element (203, 501) has contamination (601, 701) or is free of contamination (601, 701).

3. The method according to claim 1 or 2, in, When it is determined that the sensor element (203, 501) has contamination (601, 701), it is determined what type of contamination (601, 701) the contamination (601, 701) is, wherein the result additionally indicates the type of contamination (601, 701).

4. The method according to claim 3, in, A water contact signal is received, the water contact signal representing a detected contact of the surroundings of the sensor element (203, 501) with water, wherein determining the type of the contaminant (601, 701) includes determining that the type of the contaminant (601, 701) includes water.

5. The method according to claim 1 or 2, in, When it is determined that the sensor element (203, 501) has contamination (601, 701), a control signal is output to control a contamination removal process.

6. The method according to claim 5, in, When it is determined that the sensor element (203, 501) has contamination (601, 701), it is determined what type of contamination (601, 701) the contamination (601, 701) is, wherein the result additionally indicates the type of contamination (601, 701), wherein the control signal is output based on the determined type of contamination (601, 701).

7. The method according to claim 6, in, If the dirt (601, 701) includes water and / or fluid and / or biofilm, the control signal includes a drying heating control signal for controlling the heating device (205) so as to dry the sensor element (203, 501) by heating, and / or, if the dirt (601, 701) includes dust and / or solids and / or biofilm, the control signal includes a cleaning control signal for controlling a cleaning device so as to clean the sensor element (203, 501).

8. The method according to claim 1 or 2, in, The measured physical variable comprises a time profile of the physical variable, wherein the reference physical variable comprises a time profile of the reference physical variable.

9. A device (201) for detecting contamination (601, 701) of a micro-electromechanical sensor element (203, 501), the device include: - micro-electromechanical sensor element (203, 501); - a heating device (205) arranged to heat the micro-electromechanical sensor element (203, 501); and - a signal processing device (207) for implementing the method according to any one of claims 1 to 8, The signal processing device (207) has an output end (209), which is configured to output a heating control signal for controlling the heating device (205) so as to heat the sensor element (203, 501). The signal processing device (207) has an input (211) which is configured to receive a measurement signal representing a physical variable measured by means of the heated sensor element (203, 501). The signal processing device (207) has a processor (213) which is configured to determine, based on the measured physical variable, whether the sensor element (203, 501) has dirt (601, 701) or is free of dirt (601, 701). The output terminal (209) is configured to output a result signal, wherein the result signal represents a result indicating whether the sensor element (203, 501) has dirt (601, 701) or is free of dirt (601, 701). The device comprises a memory in which a reference physical variable is stored, wherein the reference physical variable and the measured physical variable have the same physical unit, wherein the input terminal (211) is configured to receive a reference signal from the memory, wherein the reference signal represents the reference physical variable, wherein the processor (213) is configured to determine based on the reference physical variable whether the sensor element (203, 501) has dirt (601, 701) or is free of dirt (601, 701), The processor (213) is configured to determine a deviation between the measured physical variable and the reference physical variable, wherein the processor (213) is configured to determine, based on the determined deviation, whether the sensor element (203, 501) has contamination (601, 701) or is free of contamination (601, 701).

10. The device (201) according to claim 9, in, The following device includes the sensor element (203, 501): the device includes a water identification device, the water identification device is configured to identify the contact between the device and water and output a water contact signal when the contact between the device and water is identified, wherein the input end (211) is configured to receive the water contact signal, wherein the processor (213) is configured to determine, based on whether the water contact signal has been received: what type of contaminant is.

11. The apparatus (201) according to claim 9 or 10, comprising a dirt removal device, the dirt removal device being arranged for carrying out a dirt removal process, in, The output end (209) is configured to output a control signal to control the dirt removal device so as to implement a dirt removal process.

12. The device (201) according to claim 11, in, The dirt removal device comprises one or more of the following: the heating device (205), a piezoelectric element for loading the sensor element (203, 501) with vibration.

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