Method for offset compensation, method for operating a pressure sensor, and pressure sensor

Abstract

The invention relates to a method for offset compensation (22) of a signal offset (42) in a measurement signal (26) from a pressure sensor (10), having the steps of providing (24) the pressure sensor (10), which provides the measurement signal (26) depending on a deflection of the sensor element (12) depending on a pressure at the pressure sensor (10) and which has an insulating compound (18) for protecting against environmental influences on the sensor element (12), sensing (28) a total acceleration (30) acting on the pressure sensor (10), comprising a gravitational acceleration component (32) and / or an acceleration (33), accessing calculation parameters (35) stored in a storage unit (34), calculating (36) an offset pressure (38), arising on the sensor element (12) at least via the mass of the insulating compound (18) and the total acceleration (30) acting thereon, depending on at least one of the calculation parameters (35) and the total acceleration (30), and compensating (40) at least the signal offset (42), corresponding to the calculated offset pressure (38), in the measurement signal (26). The invention also relates to a method for operating (58) a pressure sensor (10), and to a pressure sensor (10).

Description

[0001] Description

[0002] title

[0003] Method for offset compensation and method for operating a pressure sensor and pressure sensor

[0004] The invention relates to a method for offset compensation of a signal offset in a measurement signal of a pressure sensor according to claim 1. Furthermore, the invention relates to a method for operating a pressure sensor and a pressure sensor.

[0005] State of the art

[0006] In commonly used MEMS pressure sensors, environmental influences such as humidity, dust and chemical contamination as well as temperature fluctuations can affect the measurement signal.

[0007] DE 10 2011 077 686 A1 describes a pressure sensor comprising a housing enclosing a pressure chamber and a sensor element. The pressure chamber can be pressurized from the outside, and the sensor element is sealed with a gel for protection.

[0008] However, mechanical stresses, as well as external acceleration influences resulting from movements, vibrations or impacts, can have an even greater impact on the measurement signal when a gel coating is present.

[0009] Disclosure of the invention

[0010] According to the present invention, a method for offset compensation with the features of claim 1 is proposed. This allows the pressure sensor to have higher measurement accuracy. The pressure sensor can perform the pressure measurement more reliably. The pressure sensor can be better protected from environmental influences. 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.

[0011] The sensor element can comprise a microelectromechanical measuring element for converting a pressure applied thereto into an electrical measurement variable. The sensor element, in particular the measuring element, can comprise a sensor membrane that can be deflected depending on the pressure. The electrical measurement variable 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 an environment surrounding the sensor element, and / or a differential pressure, in particular between a front and a back of the sensor element.

[0012] The measuring signal can indicate the pressure applied to the sensor element.

[0013] 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.

[0014] 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.

[0015] The pressure sensor can have a housing in which the insulating compound is accommodated. The housing can have an opening facing the surroundings of the pressure sensor for pressure transmission between the surroundings 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 enclose it.

[0016] The gravitational acceleration component can depend on the orientation of the sensor element relative to the direction of gravitational acceleration. The gravitational acceleration component can be equal to the gravitational acceleration if the orientation of the sensor element and the direction of gravitational acceleration are parallel. The gravitational acceleration component can be positive or negative, depending on whether the orientation of the sensor element is parallel or antiparallel to the direction of gravitational acceleration. The gravitational acceleration component can be zero if the orientation of the sensor element is at an angle of 90° to the gravitational acceleration.

[0017] The total acceleration can be recorded in real time or near real time.

[0018] In a preferred embodiment of the invention, it is advantageous if the calculation parameter includes an insulating mass parameter of the insulating mass. An insulating mass parameter can be a mass value of the insulating mass. The insulating mass parameter can be determined by calibrating the pressure sensor.

[0019] The calculation parameter can specify a contact mass that rests on the sensor element, including the insulating mass. The contact mass can include deposits on the insulating mass. These deposits can be dirt, organic and / or inorganic material, water, snow, ice, dust, and / or sand. If the calculation parameter includes information on the contact mass increased compared to the insulating mass, the offset pressure resulting from at least the mass of the contact mass and the total acceleration acting on it on the sensor element can be calculated based on the calculation parameter and the total acceleration. The compensation can relate to the signal offset corresponding to the offset pressure.

[0020] In an advantageous embodiment of the invention, the calculation parameter includes a sensor element parameter of the sensor element. A sensor element parameter can be a sensor element surface coupled to the insulating compound. The sensor element surface can be a membrane surface of the sensor membrane. The sensor element surface can comprise the surface of the sensor element that is sensitive to the applied pressure and thus generates the measurement signal.

[0021] The offset pressure can be calculated as the quotient of the acceleration force resulting from the total acceleration acting on the mass of the insulating mass or the mass of the support mass, on the one hand, and the sensor element area, on the other. The acceleration force can be calculated as the product of the mass of the insulating mass or the mass of the support mass, on the one hand, and the total acceleration, on the other.

[0022] The offset pressure can be calculated as the product of the calculation parameter and the total acceleration. The calculation parameter can be specified as the quotient of the mass of the insulating mass or the mass of the support mass, on the one hand, and the sensor element area, on the other. A preferred embodiment of the invention is advantageous in which the orientation of the sensor element with respect to the gravitational acceleration is detected, and the gravitational acceleration component of the total acceleration is calculated as a function of the detected orientation. The orientation of the sensor element can be measured by an external gyroscope. The orientation of the sensor element refers to a normal of the sensor element, in particular a normal of a sensor membrane of the sensor element. The normal of the sensor membrane can be oriented in the direction of maximum deflection of the sensor membrane.

[0023] In a specific embodiment of the invention, it is advantageous if the acceleration acting on the sensor element and the insulating compound is measured, and the total acceleration is calculated based on the measured acceleration. The acceleration can be unidirectional and / or rotational acceleration. The rotational acceleration can be centrifugal acceleration. The acceleration acting on the pressure sensor can be caused by an accelerated movement, a vibration, and / or an impact. The acceleration can be measured by an external acceleration sensor.

[0024] According to the present invention, a method for operating a pressure sensor with the features of claim 6 is further proposed.

[0025] In a preferred embodiment of the invention, the signal offset compensation occurs in real time during operation of the pressure sensor. This allows the pressure measurement to be performed more accurately and reliably.

[0026] A specific embodiment of the invention further comprises the steps of measuring the signal offset under predetermined acceleration conditions with respect to a total acceleration acting on the pressure sensor, calculating a signal offset reduced to account for the influence of the total acceleration, detecting the total acceleration, calculating the calculation parameter as a function of the offset pressure corresponding to the reduced signal offset and the detected total acceleration, and storing the calculated calculation parameter in the storage unit as an updated calculation parameter to be used further in compensating the signal offset. The acceleration conditions can include a predetermined orientation of the sensor element with respect to the direction of gravity and / or a known acceleration acting on the sensor element.The acceleration conditions can be a predetermined orientation of the sensor element parallel and antiparallel to the direction of gravity, preferably in the absence of any further acceleration acting on the sensor element. In a specific embodiment of the invention, it is advantageous to infer that the contact mass on the sensor element is larger than the insulating mass if a deviation between the previously stored calculation parameter and the updated calculation parameter exceeds a predetermined deviation threshold. The larger contact mass can result from a deposit on the insulating mass, for example, due to soiling and / or contamination.

[0027] According to the present invention, a pressure sensor having the features of claim 10 is further proposed.

[0028] Further advantages and advantageous embodiments of the invention emerge from the description of the figures and the illustrations.

[0029] Character description

[0030] The invention is described in detail below with reference to the figures. They show in detail:

[0031] Figure 1: A pressure sensor in a special embodiment of the invention.

[0032] Figure 2: A method for offset compensation in a specific embodiment of the invention.

[0033] Figure 3: A method for operating a pressure sensor in a specific embodiment of the invention.

[0034] Figure 1 shows a pressure sensor in a specific embodiment of the invention. The pressure sensor 10 is preferably a micromechanical pressure sensor 10, in particular a MEMS pressure sensor 10, with a sensor element 12 and an electronics unit 14 arranged on a substrate 15. A housing 16 accommodates the sensor element 12, which preferably has a sensor membrane for pressure-dependent deflection. An insulating compound 18, preferably a gel, is arranged within the housing 16 on the sensor element 12 to protect it from environmental influences from an environment 20 of the pressure sensor 10. The insulating compound 18 preferably completely covers the sensor element 12.

[0035] The sensor element 12 with the sensor membrane converts the ambient pressure of the environment 20 of the pressure sensor 10 into an electrical signal. The electronics unit 14 is preferably designed as an integrated circuit, in particular as an ASIC, and includes a memory unit on which retrievable calculation parameters are stored. The electronics unit 14 can process the electrical signal of the sensor element 12, preferably convert it to digital, and output it as a digital measurement signal.

[0036] The orientation of the sensor element 12, to which reference will be made below, refers to a normal N of the sensor element 12. The normal N of the sensor element 12 can be oriented in the direction of a maximum deflection of the sensor membrane.

[0037] Figure 2 shows a method for offset compensation in a specific embodiment of the invention. The method for offset compensation 22 of a signal offset in a measurement signal of a pressure sensor 10 comprises providing 24 the pressure sensor 10, which, with a sensor element 12, provides a measurement signal 26 dependent on a pressure at the pressure sensor 10 and which has an insulating compound on the sensor element 12 for protection against environmental influences.

[0038] Furthermore, a detection 28 of a total acceleration 30 acting on the sensor element 12, comprising a gravitational acceleration component 32 and an acceleration 33 acting on the sensor element 12 and the insulating mass 18, takes place. Furthermore, access is made to a calculation parameter 35 stored in a memory unit 34, and a calculation 36 of an offset pressure 38 resulting from the mass of the insulating mass and the total acceleration 30 acting on the sensor element 12 is carried out depending on the at least one calculation parameter 35 and the total acceleration 30. Subsequently, a compensation 40 of the signal offset 42 corresponding to the calculated offset pressure 38 in the measurement signal 26 takes place.

[0039] The calculation parameter 35 can preferably include an insulating mass parameter 44, in particular a mass value of the insulating mass, and a sensor element parameter 46, in particular a sensor element area, of the sensor element 12. For this purpose, the calculation parameter 35 can be specified as the quotient of the mass of the insulating mass and the sensor element area. The offset pressure 38 is preferably calculated as the product of the calculation parameter 35 and the total acceleration 30.

[0040] The gravitational acceleration component 32 is detected, in particular, depending on the orientation of the sensor element 12 with respect to the gravitational acceleration, and the gravitational acceleration component 32 of the total acceleration 30 is calculated based on the detected orientation. The acceleration 33 acting on the sensor element 12 and the insulating mass is also measured, and the effective acceleration of the total acceleration 30 is calculated based on the measured acceleration. The sum of the gravitational acceleration component 32 and the acceleration 33 results in the total acceleration 30, which is taken into account when calculating the offset pressure 38.

[0041] The calculation parameter 35 is stored in the memory unit 34, which is preferably assigned to the electronics unit of the pressure sensor 10, and can be retrieved for calculating the offset pressure 38. For example, the calculation parameter 35, which includes the insulating mass parameter 44 and the sensor element parameters 46, is determined by an initial calibration 48, i.e., preferably before the initial commissioning of the pressure sensor 10, by measuring a signal offset 42 of the pressure sensor 10 under acceleration conditions 50 predetermined with respect to a total acceleration 30 acting on the sensor element 12. The predetermined acceleration conditions 50 can be two predetermined orientations of the pressure sensor 10 relative to the direction of gravity, in each case with no further acceleration acting on the pressure sensor 10.A first acceleration condition 52 can be a first orientation aligned parallel to the direction of gravitational acceleration, and a second acceleration condition 54 can be a second orientation opposite the first orientation and aligned antiparallel to the direction of gravitational acceleration. This allows the influence of the gravitational acceleration to be determined as the sole total acceleration 30 during calibration 48 on the insulating mass and, consequently, on the sensor element 12, and the signal offset 42 as a reduced signal offset 56.

[0042] Subsequently, the calculation parameter is calculated as an updated calculation parameter 35' depending on the reduced signal offset 56 and the acceleration due to gravity as total acceleration 30 and stored in the memory unit 34 so that it can be retrieved.

[0043] Figure 3 shows a method for operating a pressure sensor in a specific embodiment of the invention. The method for operating 58 of the pressure sensor 10 comprises providing 24 the pressure sensor 10, which, with a sensor element 12, provides a measurement signal 26 dependent on a pressure at the pressure sensor 10 and has an insulating compound on the sensor element 12 for protection against environmental influences.

[0044] During operation of the pressure sensor 10, a compensation 40 of a signal offset 42 corresponding to an offset pressure 38, which arises via the mass of the insulating compound and the total acceleration 30 acting on the sensor element 12, is preferably carried out by the method described in Figure 2, in particular in real time during operation, depending on the calculation parameter 35 stored in the memory unit 34 and the determined total acceleration 30.

[0045] During operation of the pressure sensor 10, a regular calibration 60 can be carried out regularly and / or on request, which proceeds similarly to the initial calibration described with regard to the method in Figure 2. In this case, a signal offset 42 of the pressure sensor 10 is measured under acceleration conditions 50 predetermined in relation to a total acceleration 30 acting on the sensor element 12. The predetermined acceleration conditions 50 can be two predetermined orientations of the pressure sensor 10 relative to the direction of gravity, with no further acceleration acting on the pressure sensor 10 in each case. A first acceleration condition 52 can be a first orientation that is oriented parallel to the direction of gravity, and a second acceleration condition 54 can be a second orientation opposite the first orientation and oriented antiparallel to the direction of gravity.As a result, the influence of the acceleration due to gravity can be determined as the sole total acceleration 30 on the insulating mass during the regular calibration 60 and, via this, on the sensor element 12 and the signal offset 42 as a reduced signal offset 56.

[0046] Subsequently, the calculation parameter is calculated as an updated calculation parameter 35' depending on the reduced signal offset 56 and the gravitational acceleration as the total acceleration 30 and stored retrievably in the memory unit 34. Furthermore, it is concluded that the contact mass on the sensor element 12 is larger than the insulating mass if, during a check 62, a deviation 63 between the previously stored calculation parameter 35 and the updated calculation parameter 35' exceeds a predetermined deviation threshold 64. If the deviation 63 exceeds the deviation threshold 64, information 65 can be output indicating contamination of the pressure sensor 10.

Claims

Patent claims 1. Method for offset compensation (22) of a signal offset (42) in a measurement signal (26) of a pressure sensor (10), comprising the steps Providing (24) the pressure sensor (10), which provides the measurement signal (26) depending on a deflection of the sensor element (12) dependent on a pressure at the pressure sensor (10) and which has an insulating compound (18) for protection against environmental influences on the sensor element (12), detecting (28) a total acceleration (30) acting on the pressure sensor (10) comprising a gravitational acceleration component (32) and / or an acceleration (33), Access to calculation parameters (35) stored in a memory unit (34), calculation (36) of an offset pressure (38) which is generated at least via the mass of the insulating mass (18) and the total acceleration (30) acting thereon on the sensor element (12) as a function of at least one of the calculation parameters (35) and the total acceleration (30) and Compensation (40) of at least the signal offset (42) corresponding to the calculated offset pressure (38) in the measurement signal (26).

2. Method for offset compensation (22) according to claim 1, characterized in that the calculation parameter (35) is an insulating mass parameter (44) of the insulating mass (18).

3. Method for offset compensation (22) according to claim 1 or 2, characterized in that the calculation parameter (35) includes a sensor element parameter (46) of the sensor element (12).

4. Method for offset compensation (22) according to one of the preceding claims, characterized in that an orientation of the sensor element (12) with respect to the gravitational acceleration is detected and the gravitational acceleration component (32) of the total acceleration (30) is calculated as a function of the detected orientation.

5. Method for offset compensation (22) according to one of the preceding claims, characterized in that the acceleration acting on the sensor element (12) and the insulating mass (18) is measured and the acceleration (33) of the total acceleration (30) is calculated as a function of the measured acceleration.

6. Method for operating (58) a pressure sensor (10), comprising the steps of providing (24) the pressure sensor (10), which provides a measurement signal (26) dependent on a pressure at the pressure sensor (10) with a sensor element (12) and which provides an insulating compound (18) for protection against environmental influences on the sensor element (12), compensation (40) of a signal offset (42) corresponding to an offset pressure (38) which arises at least via the mass of the insulating mass (18) and the total acceleration (30) acting thereon on the sensor element (12), by means of a method for offset compensation (22) according to one of the preceding claims.

7. Method of operation (58) according to claim 6, characterized in that during operation of the pressure sensor (10) the compensation (40) of the signal offset (42) takes place in real time.

8. A method of operation (58) according to claim 6 or 7, further comprising the steps of measuring the signal offset (42) under acceleration conditions (50) predetermined with respect to a total acceleration (30) acting on the pressure sensor (10), calculating (36) a signal offset (56) reduced to the influence of the total acceleration (30), Detecting (28) the total acceleration (30), calculating (36) the calculation parameter (35) as a function of the offset pressure (38) corresponding to the reduced signal offset (56) and the detected total acceleration (30), and storing the calculated updated calculation parameter (35') in the storage unit (34) as a calculation parameter (35) to be used further in the compensation (40).

9. Method for operation (58) according to claim 8, characterized in that it is concluded that a larger contact mass on the sensor element (12) than the insulating mass (18) is used if a deviation between the previously stored calculation parameter (35) and the updated calculation parameter (35') exceeds a predetermined deviation threshold.

10. Pressure sensor (10) which, with a sensor element (12), provides a measurement signal (26) depending on a deflection of the sensor element (12) which is dependent on a pressure at the pressure sensor (10), and which has an insulating compound (18) for protection against environmental influences on the sensor element (12), and which is designed to be operated by a method for operating (58) a pressure sensor (10) according to one of claims 6 to 9.

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