Method for detection, method for compensation, method for operation, and pressure sensor

Abstract

The invention relates to a method for detecting (32) a signal influence (28) of a bearing mass (22) on a sensor element (18) of a pressure sensor (14), comprising the steps of providing (12) the pressure sensor (14), which provides a measurement signal (16) dependent on a deflection of the sensor element (18) dependent on a pressure (p) at the pressure sensor (14) and which has the bearing mass (22), which faces the sensor environment (20) and influences the measurement signal (16), on the sensor element (18), exciting (44) the sensor element (18) with an electrical excitation signal (46), detecting (48) the response signal (50) of the sensor element (18) to the excitation signal (46), comparing (52) the response signal (50) with a stored reference signal (54), wherein an influence parameter (C) is calculated as at least one quantitative characteristic variable of the bearing mass (22) that contributes to the signal influence (28) on the measurement signal (16) due to an acceleration sensitivity of the pressure sensor (14) by comparing (52) a frequency curve (56) of the response signal (50) with a frequency curve (58) of the reference signal (54). The invention further relates to a method for compensation (20), a method for operation (10), and a pressure sensor (14).

Description

[0001] Description

[0002] title

[0003] Method of detection, method of compensation, method of operation and pressure sensor

[0004] The invention relates to a method for detecting a signal influence according to the preamble of claim 1. Furthermore, the invention relates to a method for compensating a signal influence, a method for operating a pressure sensor and a pressure sensor.

[0005] State of the art

[0006] DE 10 2020 209 856 A1 describes a method for determining the condition of a pressure sensor with a deflectable micromechanical sensor structure. In this method, the micromechanical sensor structure is excited with an electrical excitation signal, the response of the sensor structure is recorded, this is compared with a reference response, and an assessment of the sensor condition with regard to the presence of a deposit is made. The response can be a resonance frequency or a quality factor. If the presence of a deposit is detected, corrective measures are initiated to remove the deposit.

[0007] Disclosure of the invention

[0008] According to the present invention, a detection method with the features of claim 1 is proposed. This allows the extent of the signal influence on the measurement signal caused by the contact mass to be detected, and preferably a signal component of the signal influence can be calculated and compensated. Even in the presence of deposits on the sensor element, the pressure sensor can be operated reliably. The measurement accuracy of the pressure sensor is increased. The pressure sensor can be a microelectromechanical pressure sensor (MEMS pressure sensor). The pressure sensor can be installed in a vehicle, an aircraft, a watercraft, an industrial product, and / or a consumer product. The consumer product can be a mobile device, in particular a smartphone or a wearable, preferably a smartwatch.

[0009] The sensor element can be a microelectromechanical sensor element for converting a pressure applied thereto into an electrical measurement signal. The sensor element can comprise a sensor membrane that can be deflected depending on the pressure. The measurement signal can be dependent on the deflection of the sensor membrane. For this purpose, the sensor element can have piezoresistive, piezoelectric, optical, and / or capacitive conversion means. The pressure applied to the sensor element and to be measured can be an absolute pressure, preferably an ambient pressure of a sensor environment of the sensor element and / or a differential pressure, in particular between a front and a back of the sensor element.

[0010] The pressure sensor can be a capacitive pressure sensor. The sensor element can have a movable electrode. The electrode can be deflectable relative to a fixed counter electrode. The measurement signal can depend on a distance between the electrode and the counter electrode, which is determined by the deflection of the sensor element.

[0011] Acceleration sensitivity is the pressure sensor's cross-sensitivity to accelerations. This can affect the measurement signal indicating the pressure applied to the pressure sensor, disrupting the pressure measurement. Acceleration sensitivity can be due to accelerations such as gravitational acceleration and / or linear and / or rotational acceleration acting externally on the pressure sensor.

[0012] The signal influence of the support mass can arise from an acceleration force acting on the sensor element, which depends on the mass of the support mass and the acceleration. Depending on the sensor surface of the sensor element where the acceleration force is effectively applied, the acceleration force can correspond to a pressure component, which constitutes a signal component of the signal influence in the measurement signal.

[0013] The reference signal can be stored in a memory unit. The memory unit can be part of the pressure sensor. The memory unit can be an integrated circuit, in particular an FPGA or ASIC. The memory unit can be assigned to an electronic unit of the pressure sensor. The electronic unit can digitally convert and / or output the measurement signal.

[0014] The support mass may comprise an insulating mass that separates, preferably seals, the sensor element from the sensor environment. The support mass may be formed from the insulating mass and deposits on a side of the insulating mass facing away from the sensor element and toward the sensor environment.

[0015] The insulating compound can comprise a gel and / or oil. The insulating compound can be viscoelastic. The insulating compound can be arranged primarily, preferably exclusively, to protect the sensor element from environmental influences. The insulating compound can be liquid or semi-liquid. The insulating compound can be either solid or gaseous. The insulating compound can partially or completely cover the sensor element.

[0016] The deposits can be unwanted materials, substances, or compounds on the insulation compound. The deposits can be dirt, organic and / or inorganic material, water, snow, ice, dust, and / or sand.

[0017] The pressure sensor can have a housing in which the insulating compound is accommodated. The housing can have an opening facing the sensor environment of the pressure sensor for pressure transmission between the sensor environment of the pressure sensor and the sensor element or the insulating compound. The sensor element can be arranged on a side facing away from the opening with respect to the insulating compound. The housing can accommodate the sensor element, preferably surround or border it.

[0018] The excitation signal can comprise a frequency range including at least one expected resonant frequency of the sensor element. The excitation signal can be a temporal frequency sweep or a simultaneous broadband frequency superposition. The frequency superposition can be an electrical voltage pulse.

[0019] The excitation signal can be offset in time from the response signal. The excitation with the excitation signal and the detection of the response signal can be separated in time. The excitation signal can be directed to the sensor element using an excitation element, for example, an excitation electrode. The excitation with the excitation signal and the detection of the response signal can occur simultaneously.

[0020] The quantitative parameter can take various values. The signal influence can depend at least on the parameter. The parameter can influence the signal influence by causally depending on the parameter and at least one other parameter. In addition to the influencing parameter, the acceleration acting on the pressure sensor can influence the signal.

[0021] The influence parameter can be calculated if the comparison reveals a deviation between the response signal and the reference signal. The reason for the calculation can depend on the comparison. The influence parameter can be calculated quantitatively based on information from the response signal and the reference signal, or based only on information from the response signal. Information from the response signal and / or the reference signal can be used to calculate the influence parameter.

[0022] In a preferred embodiment of the invention, it is advantageous if the influencing parameter comprises a mass value of the coating mass. The influencing parameter can correspond to the mass value, i.e., the mass, of the coating mass. The influencing parameter can specify the mass value of the coating mass directly or indirectly.

[0023] The influencing parameter can be the thickness of the support compound on the sensor element. The influencing parameter can be the thickness of the insulating compound, in particular the thickness of the gel layer.

[0024] In an advantageous embodiment of the invention, a resonant frequency and / or a quality factor of the resonance elevation in the frequency response of the response signal is determined. The resonant frequency and the quality factor are preferably dependent on a pressure and the mass of the support mass. A larger mass of the support mass can reduce the resonant frequency and / or change the resonance elevation described by the quality factor.

[0025] The resonance frequency can correspond to the natural frequency of the sensor element with support mass or a multiple of the natural frequency of the sensor element with support mass.

[0026] In a specific embodiment of the invention, it is advantageous if the influencing parameter is calculated as a function of the resonant frequency and / or the quality factor. The influencing parameter can correlate with the resonant frequency and / or the quality factor.

[0027] The correlation between the influencing parameter and the resonance frequency and / or the quality factor can be determined and saved before initial commissioning of the pressure sensor. The correlation can be checked and adjusted if necessary during operation of the pressure sensor.

[0028] In a specific embodiment of the invention, it is advantageous if the influencing parameter is calculated based on a previously known relationship between the resonant frequency in the frequency response and a mass of the support mass. The previously known relationship can be stored in a memory unit.

[0029] In a specific embodiment of the invention, it is advantageous if the influencing parameter is calculated based on a previously known relationship between the quality factor of the resonance elevation and the mass of the support mass. Preferably, the influencing parameter is calculated based on a previously known relationship between the resonance frequency and the quality factor, on the one hand, and the mass of the support mass, on the other.

[0030] The previously known relationship can take into account other environmental influences, in particular temperature influences.

[0031] The previously known relationship can be stored in a memory unit. The previously known relationship can be stored in the memory unit in which the reference signal is also stored. The memory unit can be a component of the pressure sensor. The memory unit can be an integrated circuit, in particular an FPGA or ASIC. The memory unit can be assigned to an electronic unit of the pressure sensor. The electronic unit can digitally convert and / or output the measurement signal.

[0032] A preferred embodiment of the invention is advantageous in which the frequency response of the reference signal has been determined by at least two measurements, each involving excitation and detection of the response signal at mutually different orientations of the pressure sensor with respect to the direction of gravitational acceleration. A first measurement involving excitation and detection of the response signal can be performed with a first orientation of the pressure sensor, in particular with a parallel orientation, with respect to the gravitational acceleration, and a second measurement involving excitation and detection of the response signal can be performed with an opposite second orientation of the pressure sensor, in particular with an antiparallel orientation, with respect to the gravitational acceleration.

[0033] The reference signal can be determined before the pressure sensor is commissioned for the first time. The reference signal can be a reference signal determined from a pressure sensor of the same or similar design as described above.

[0034] According to the present invention, a method for compensating for a signal influence is further proposed, having the features of claim 8. The acceleration can be measured by an external acceleration sensor.

[0035] According to the present invention, a method for operating a pressure sensor with the features of claim 9 is further proposed. According to the present invention, a pressure sensor with the features of claim 10 is further proposed.

[0036] Further advantages and advantageous embodiments of the invention emerge from the description of the figures and the illustrations.

[0037] Character description

[0038] The invention is described in detail below with reference to the figures. They show in detail:

[0039] Figure 1: A method for operating a pressure sensor in a specific embodiment of the invention.

[0040] Figure 2: A method for determining a reference signal for the detection method in a specific embodiment of the invention.

[0041] Figure 3: A pressure sensor and a response signal when carrying out a method for detecting a signal influence in a special embodiment of the invention.

[0042] Figure 4: The pressure sensor from Figure 3 and a response signal when deposits are present.

[0043] Figure 1 shows a method for operating a pressure sensor in a specific embodiment of the invention. The method for operating 10 a pressure sensor initially comprises providing 12 the pressure sensor 14, which provides a measurement signal 16 as a function of a deflection of a sensor element 18 that is dependent on a pressure p at the pressure sensor 14, and which has a support mass 22 on the sensor element 18 facing the sensor environment 20 and influencing the measurement signal 16. During operation of the pressure sensor 14, compensation 24 is carried out by a method for compensating 26 a signal influence 28 of the support mass 22 on the sensor element 18 of the pressure sensor 14, which signal influence arises via an acceleration sensitivity.

[0044] The support mass 22 can comprise an insulating mass that separates, preferably seals, the sensor element 18 from a sensor environment 20. The insulating mass can be a gel. The sensor element 18 can be a microelectromechanical sensor element 18 for converting a pressure p applied thereto into the electrical measurement signal 16 and can comprise a sensor membrane that can be deflected depending on the pressure p.

[0045] The compensation method 26 comprises, in addition to providing 12 the pressure sensor 14, calculating 30 an influencing parameter C of the support mass 22 by a method for detecting 32 a signal influence 28 of the support mass 22 on the sensor element 18 of the pressure sensor 14, measuring 34 an acceleration a acting on the pressure sensor 14 with the sensor element 18 and the support mass 22, calculating 38 a signal component 40 of the signal influence 28 on the measurement signal 16 as a function of the measured acceleration a and the calculated influencing parameter C, and compensating 24 the signal component 40 in the measurement signal 16.

[0046] The method for detecting 32 a signal influence 28 of the support mass 22 on the sensor element 18 of the pressure sensor 14 comprises, in addition to providing 12 the pressure sensor 14, exciting 44 the sensor element 18 with an electrical excitation signal 46, detecting 48 the response signal 50 of the sensor element 18 to the excitation signal 46, and comparing 52 the response signal 50 with a stored reference signal 54. The comparison 52 includes a comparison 52 of a frequency curve 56 of the response signal 50 with a frequency curve 58 of the reference signal 54.

[0047] Depending on the comparison 52, for example if there is a deviation between the frequency curves 56, 58, the influencing parameter C is calculated as at least one characteristic of the support mass 22, wherein the influencing parameter C causes the signal influence 28 on the measurement signal 16 via an acceleration sensitivity of the pressure sensor 14. The influencing parameter C can comprise a mass value m of the support mass 22. When acceleration a acts on the pressure sensor 14, the mass of the support mass 22 causes an acceleration force acting on the sensor element 18 with a deflectable sensor membrane, which, depending on a membrane area, corresponds to a pressure component that causes the signal component 40 of the signal influence 28 in the measurement signal 16.

[0048] In the frequency response 56 of the response signal 50, a resonance frequency fr and a quality factor G of the resonance elevation in the frequency response 56 are preferably determined. The influencing parameter C is calculated in particular as a function of the resonance frequency fr and the quality factor G. For this purpose, the influencing parameter C is calculated as a function of a previously known relationship 60 between the resonance frequency fr and the quality factor G in the frequency response 56 and the influencing parameter C, in particular the mass m of the support mass 22. Figure 2 shows a method for determining a reference signal for the detection method in a specific embodiment of the invention.The frequency curve 58 of the reference signal 54 has been determined in advance, for example, in particular before initial commissioning of the pressure sensor 14, by at least two measurements, each involving excitation 44 and detection 48 of the response signal 50, with mutually different orientations of the pressure sensor 14 with respect to the acceleration due to gravity. With a first measurement 62, the sensor element 18 is excited with the excitation signal 46. The pressure sensor 14 is aligned parallel to the direction of acceleration 64 due to gravity, i.e., the support mass 22 points upward. The response signal 50 of the sensor element 18 is subsequently detected. With a second measurement 66, in which the pressure sensor 14 is aligned antiparallel to the direction of acceleration 64 due to gravity, i.e., the support mass 22 points downward, the sensor element 18 is excited by the excitation signal 46, and the response signal 50 of the sensor element 18 is detected.

[0049] Subsequently, the two response signals 50 are compared with each other in a comparison 68 and the reference signal 54 is calculated therefrom.

[0050] Figure 3 shows a pressure sensor and a response signal during the execution of a method for detecting a signal influence in a specific embodiment of the invention. Figure 3 a) shows the pressure sensor 14 with the sensor element 18 and an insulating compound, for example a gel, as a support compound 22 on the sensor element 18. Figure 3 b) shows the response signal 50 of the sensor element 18 after an excitation signal. The frequency curve 56 of the response signal 50 exhibits a resonance peak 70 at the resonance frequency fr. The resonance peak 70 has a quality factor G that describes a width 72 of the resonance peak 70.

[0051] Figure 4 shows the pressure sensor from Figure 3 and a response signal when executing a method for detecting a signal influence in the presence of a deposit. Figure 4 a) shows the pressure sensor 14 with the sensor element 18 and the insulating mass 74 with a deposit 76. The support mass 22 is thus formed by the insulating mass 74 and the deposit 76. Figure 4 b) shows the response signal 50 of the sensor element 18 after an excitation signal. The frequency curve 58 of the response signal 50 has a resonance frequency fr that is lower than the resonance frequency from Figure 3 b). The resonance elevation 70 has a higher quality factor G than the quality factor G from Figure 3 b), which is caused by greater damping of the resonance oscillation by the support mass 22.

Claims

Patent claims 1 . Method for detecting (32) a signal influence (28) of a support mass (22) on a sensor element (18) of a pressure sensor (14), comprising the steps of providing (12) the pressure sensor (14), which provides a measurement signal (16) depending on a deflection of the sensor element (18) dependent on a pressure (p) at the pressure sensor (14) and which has the support mass (22) on the sensor element (18) facing the sensor environment (20) and influencing the measurement signal (16), Excitation (44) of the sensor element (18) with an electrical excitation signal (46), detection (48) of the response signal (50) of the sensor element (18) to the excitation signal (46), comparison (52) of the response signal (50) with a stored reference signal (54), characterized in that depending on a comparison (52) of a frequency curve (56) of the response signal (50) with a frequency curve (58) of the reference signal (54), an influencing parameter (C) is calculated as at least one quantitative characteristic of the support mass (22) which contributes to the signal influence (28) on the measurement signal (16) due to an acceleration sensitivity of the pressure sensor (14).

2. Method for detection (32) according to claim 1, characterized in that the influencing parameter (C) comprises a mass value (m) of the support mass (22).

3. Method for detection (32) according to claim 1 or 2, characterized in that in the frequency curve (56) of the response signal (50) a resonance frequency (fr) and / or a quality factor (G) of the resonance elevation (70) in the frequency curve (56) is determined.

4. Method for detection (32) according to claim 3, characterized in that the influencing parameter (C) is calculated as a function of the resonance frequency (fr) and / or the quality factor (G).

5. Method for detection (32) according to claim 3 or 4, characterized in that the influencing parameter (C) is calculated as a function of a previously known relationship (60) between the resonance frequency (fr) in the frequency curve (56) and a mass (m) of the support mass (22).

6. Method for detection (32) according to one of claims 3 to 5, characterized in that the influencing parameter (C) is calculated as a function of a previously known relationship (60) between the quality factor (G) of the resonance elevation (70) and the mass (m) of the support mass (22).

7. A method for detection (32) according to any one of the preceding claims, characterized in that the frequency curve (58) of the reference signal (54) has been determined by at least two measurements, each with excitation (44) and detection (48) of the response signal (50) at mutually different orientations of the pressure sensor (14) with respect to a direction of gravitational acceleration (64).

8. A method for compensating (26) a signal influence (28) of a support mass (22) on a sensor element (18) of a pressure sensor (14) arising from an acceleration sensitivity, comprising the steps of providing (12) the pressure sensor (14) which provides a measurement signal (16) depending on a deflection of the sensor element (18) dependent on a pressure (p) at the pressure sensor (14) and which has the support mass (22) on the sensor element (18) facing the sensor environment (20) and influencing the measurement signal (16), Calculating (30) an influencing parameter (C) of the support mass (22) by a detection method (32) according to one of the preceding claims, measuring (34) an acceleration (a) acting on the pressure sensor (14) with the sensor element (18) and the support mass (22), calculating (38) a signal component (40) of the signal influence (28) on the measurement signal (16) as a function of the measured acceleration (a) and the calculated influencing parameter (C) and compensating (24) the signal component (40) in the measurement signal (16).

9. Method for operating (10) a pressure sensor (14) comprising the steps Providing (12) the pressure sensor (14), which provides a measurement signal (16) depending on a deflection of the sensor element (18) dependent on a pressure (p) at the pressure sensor (14) and which has the support mass (22) on the sensor element (18) facing the sensor environment (20) and influencing the measurement signal (16), Compensation (24) by a compensation method (26) according to claim 8.

10. Pressure sensor (14) which, with a sensor element (18), provides a measurement signal (16) depending on a deflection of the sensor element (18) which is dependent on a pressure (p) at the pressure sensor (14), and which has an insulating compound for protection against environmental influences on the sensor element (18), and which is designed to be operated by a method for operation (10) according to claim 9.

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