Pressure sensor and method for operating a pressure sensor

Abstract

The pressure sensor comprises at least a micromechanical sensor element having at least one pressure-sensitive diaphragm with a diaphragm electrode spanning a cavity in a base material. A fixed counter electrode is arranged within the cavity and forms with the diaphragm electrode a first measuring capacitance for detecting a first measuring pressure. A reference capacitance is arranged within the cavity and comprises at least a first and a second fixed reference electrode. The pressure sensor is operable in at least one first operating mode in which the first measuring capacitance and the first reference capacitance are interconnected in a first bridge circuit. The pressure sensor is operable in at least one second operating mode in which the diaphragm electrode, the counter electrode and the reference electrodes are interconnected with one another such that the diaphragm electrode together with the at least one first reference electrode forms a second measuring capacitance for detecting a second measuring pressure.

Description

Technical Field

[0001] This invention relates to a pressure sensor and a method for operating the pressure sensor. Background Technology

[0002] Pressure sensors with microelectromechanical systems (MEMS) for capacitive pressure measurement are known in the prior art. Typically, such pressure sensors are used primarily in the pressure range of 300 to 1100 mBar. Pressure sensors can be optimized within this pressure range, for example, to improve their sensitivity, thereby enabling the detection of small changes in ambient pressure. This, for instance, can enable floor identification within the scope of interior space navigation.

[0003] However, in certain applications, higher pressure may also be effective, such as when a temporary pressure spike occurs. One example of this is so-called in-ear headphones with integrated pressure sensors, which are inserted into the ear and where pressure equalization cannot be achieved for a short period. Thus, the pressure sensor in such headphones can be used, for example, to detect whether the headphones are in the ear, thereby allowing music to be started, for example.

[0004] Another application area is in underwater computers, where pressure sensors must also cover a higher pressure range during dives. Larger pressure variations also occur during diving compared to air. In this case, the lower sensitivity of the pressure sensor compared to the ambient pressure range is acceptable. It is known to use multiple pressure sensors for different pressure ranges. Summary of the Invention

[0005] One object of the present invention is to provide an improved pressure sensor and to illustrate a method for operating the pressure sensor. This object is achieved by a pressure sensor having corresponding features according to the invention and a method for operating the pressure sensor having corresponding features according to the invention. Advantageous extensions are described in preferred embodiments.

[0006] The pressure sensor includes at least one micromechanical sensor element having at least one pressure-sensitive diaphragm. The diaphragm spans a cavity in a substrate material and has diaphragm electrodes. At least one fixed counter electrode is disposed within the cavity and, together with the diaphragm electrodes, forms a first measuring capacitance for detecting a first measuring pressure. At least one reference capacitor is disposed within the cavity and includes at least one fixed first and second reference electrodes. The pressure sensor is characterized in that it is capable of operating in at least one first operating mode, in which the first measuring capacitance and the first reference capacitor are interconnected in a first bridge circuit, and that it is capable of operating in at least one second operating mode, in which the diaphragm electrodes, the counter electrode, and the reference electrode are interconnected such that the diaphragm electrodes, together with at least one first reference electrode, form a second measuring capacitance for detecting a second measuring pressure.

[0007] This pressure sensor is based on the concept of extended measurement range. This extended measurement range can be advantageously achieved by enabling the pressure sensor to operate in two modes, which differ from each other in the electrical interconnections of the pressure sensor components, thereby allowing the use of different measuring capacitances, for example, in different measurement pressure ranges. The measuring capacitance can be read directly. The advantage here is that no changes are required at the micromechanical sensor element. Only the interconnections with the application-specific integrated circuit (ASIC) of the pressure sensor (on which the micromechanical sensor element is arranged) or the switching structure within the ASIC need to be modified or added.

[0008] In one embodiment, the pressure sensor is characterized by a first operating mode corresponding to a first measurement pressure range and a second operating mode corresponding to a second measurement pressure range. For example, the first operating mode can be used within a range of ambient pressure conditions. For example, the second operating mode can be set for higher pressures compared to the first operating mode.

[0009] In one embodiment, the pressure sensor is characterized in that the diaphragm and the counter electrode are designed and arranged such that the first measuring capacitance is related to the measured pressure in a first operating mode and independent of the measured pressure in a second operating mode. The diaphragm and at least one first reference electrode are designed and arranged such that the second measuring capacitance is related to the measured pressure in the second operating mode. This can be achieved, for example, by supporting the diaphragm electrode at the counter electrode from a certain pressure, thereby short-circuiting the first measuring capacitance. The second measuring capacitance is then constructed by reconnecting and operating the micromechanical sensor elements in the short-circuited state.

[0010] In one implementation, the pressure sensor is characterized by circuitry configured for controllable switching between operating modes of the pressure sensor. For example, the switching of operating modes can be achieved via individual switches or multiplexers. These are typically implemented on an ASIC.

[0011] In one embodiment, the pressure sensor is characterized in that the circuitry is configured to switch between operating modes of the pressure sensor based on a detected first measured pressure and / or based on a detected second measured pressure.

[0012] In one embodiment, the pressure sensor is characterized by circuitry configured to switch between operating modes of the pressure sensor at pre-given time intervals. Advantageously, this allows the measurements from two measuring capacitors to be used for efficient switching to the currently preferred operating mode. For example, the first operating mode may be substantially active. However, the second operating mode is activated at a certain frequency. Thus, the two measuring capacitors can be used for reliability verification of the measured pressure range, for switching between measured pressure ranges, and for fault diagnosis.

[0013] In one embodiment, the pressure sensor is characterized in that, in a first operating mode, a supply voltage is applied between a diaphragm electrode and at least one first reference electrode, and a bridge circuit tap (Abgriff) is constructed between a counter electrode and at least one second reference electrode. In a second operating mode, the supply voltage is applied at both the diaphragm electrode and the counter electrode, and at least one first reference electrode acts as a measurement tap. The supply voltage may, for example, involve a periodic signal, such as a square wave signal. The tap or measurement tap is connected to analysis and processing circuitry.

[0014] In one embodiment, the pressure sensor is characterized in that, in a second operating mode, the counter electrode and at least one second reference electrode are shorted. Thus, the second reference electrode can also be shorted to the diaphragm electrode or to the diaphragm. This avoids constructing a Hertzian dipole in the region of the second measuring capacitor. Advantageously, this reduces interference with the second measuring capacitor and other components (e.g., electrical wires) in the second operating mode of the pressure sensor.

[0015] In one embodiment, the pressure sensor is characterized in that, in a second operating mode, a second measuring capacitor is interconnected with at least one high-voltage reference capacitor in a second bridge circuit. Advantageously, the pressure sensor can thus have higher accuracy and lower susceptibility to interference effects such as noise or temperature changes within a second measuring pressure range.

[0016] In one embodiment, the pressure sensor is characterized in that the micromechanical sensor element comprises at least two sensor structures, each having a pressure-sensitive diaphragm spanning a cavity in a matrix material. Each sensor structure is equipped with at least one first measuring capacitor and a reference capacitor, the first measuring capacitor being used to detect a first measuring pressure. In a first operating mode, the first measuring capacitors and reference capacitors of the at least two sensor structures are interconnected in a first full-bridge circuit, thereby enabling differential detection of the first measuring pressure. In a second operating mode, the diaphragm electrode, counter electrode, and reference electrode of each of the at least two sensor structures are interconnected such that the diaphragm electrode, together with at least one reference electrode, respectively forms a second measuring capacitor, the second measuring capacitor being used to detect a second measuring pressure. Compared to known solutions with multiple separate sensor structures, this pressure sensor is space-saving in construction and cost-effective in manufacturing.

[0017] In a method for operating a pressure sensor according to one of the embodiments described above, each operating mode of the pressure sensor is associated with a defined pressure range. The method is characterized by monitoring a target measuring pressure by detecting and analyzing a first measuring pressure and / or a second measuring pressure, identifying a currently preferred operating mode of the pressure sensor based on the analysis of the detected measuring pressure, and switching to the currently preferred operating mode when the pressure sensor is currently in an operating mode different from the preferred operating mode.

[0018] In pressure measurement analysis, not only the current pressure measurement value but also the average pressure value over a predetermined time period is typically considered. This advantageously avoids overly frequent switching between operating modes, such as when the pressure to be measured falls within a first and second measurement pressure range. Similarly, switching can be achieved using hysteresis. Here, switching from one pressure range to another occurs when the pressure is above or below a predetermined first pressure value; however, switching occurs in the opposite direction when the pressure is above or below a predetermined second pressure value, which differs from the first pressure value. This also avoids overly frequent switching.

[0019] In one embodiment, the method is characterized in that when there is a short circuit between the diaphragm electrode and the counter electrode of the first measuring capacitor, the pressure sensor is operated in a second operating mode, and the first and second operating modes of the pressure sensor are switched according to whether there is a short circuit between the diaphragm electrode and the counter electrode of the first measuring capacitor.

[0020] In one embodiment, the method is characterized by switching between various operating modes of the pressure sensor at pre-given time intervals, and analyzing subsequently detected first or second measured pressures in terms of functional monitoring of the pressure sensor and / or reliability verification of pressure measurements. Advantageously, functional monitoring can be used to detect diaphragm rupture, deposits on the diaphragm, blockage of the diaphragm, or interruptions in the electrical wires. Attached Figure Description

[0021] The pressure sensor and the method for operating it are illustrated in more detail below with reference to the diagram. The diagram shows:

[0022] Figure 1 An exemplary micromechanical sensor element of a pressure sensor according to one embodiment, shown in a cross-sectional view;

[0023] Figure 2 In the first operating mode Figure 1 Electrical interconnections of micromechanical sensor elements;

[0024] Figure 3 In the second operating mode Figure 1 Micromechanical sensor elements;

[0025] Figure 4 Electrical interconnection of the second measuring capacitor of the micromechanical sensor element in the second operating mode;

[0026] Figure 5 : An exemplary pressure sensor;

[0027] Figure 6: An exemplary pressure sensor assembly with a full-bridge circuit according to another embodiment;

[0028] Figure 7 In the second operating mode, the second measuring capacitor of the micromechanical sensor element is electrically interconnected with the two sensor structures in an exemplary manner.

[0029] Figure 8 : Figure 7 The electrical interconnections, wherein the sensor structures are connected to the high-voltage reference capacitor in a half-bridge circuit; and

[0030] Figure 9 Method steps for operating a pressure sensor. Detailed Implementation

[0031] Figure 1 An exemplary micromechanical sensor element 1 of a pressure sensor according to one embodiment is schematically shown in cross-sectional view. The pressure sensor may also have multiple micromechanical sensor elements 1. For example, the micromechanical sensor elements 1 can be manufactured using known semiconductor manufacturing methods.

[0032] The micromechanical sensor element 1 has a substrate material 2 and at least one diaphragm 3. The substrate material 2 and the diaphragm 3 may be, for example, made of a semiconductor material, such as silicon. The diaphragm spans a cavity 4 in the substrate material 2. The diaphragm 2 is configured to be pressure sensitive and capable of deflection in response to changes in ambient pressure.

[0033] The diaphragm 3 has a diaphragm electrode 5. The diaphragm electrode 5 is exemplarily arranged within the cavity 4 and configured in a stamp-like shape. However, the membrane electrode 5 can also be constructed differently. For example, the membrane electrode 5 can be constructed as a planar electrode and disposed within the cavity 4 of the membrane 3. The membrane electrode 5 can also be formed at least through a portion of the membrane 3 itself. In this case, the... Figure 1 The stamp-like structure shown depicts a first measuring capacitor 7 formed by at least a portion of the diaphragm 3 and a counter electrode 6 forming the diaphragm electrode 5. At least one fixed counter electrode 6 is arranged within the cavity 4 and, together with the diaphragm electrode 5, forms the first measuring capacitor 7 for detecting a first measuring pressure. The diaphragm 3 can have a flexible region 8 and a rigid region 9 via the diaphragm electrode 5. In this way, the elastic properties of the diaphragm 3 can be advantageously modified and matched.

[0034] A reference capacitor 10 is arranged in the cavity 4. The reference capacitor 10 includes at least one fixed first reference electrode 11 and a fixed second reference electrode 12. Figure 1In an exemplary embodiment, additionally, another reference capacitor 13, having another fixed first reference electrode 14 and another fixed second reference electrode 15, is arranged within the cavity 4; however, this other reference capacitor may also be omitted. The first measuring capacitor 7 and the reference capacitor 10 are arranged close to each other, thereby subjecting the first measuring capacitor and the reference capacitor to the same environmental influences, such as temperature changes.

[0035] The pressure sensor is capable of operating in at least one first operating mode and at least one second operating mode. The first and second operating modes differ in the interconnection of electrodes 3, 5, 6, 11, 12, 14, and 15 of the micromechanical sensor element 1. To switch between operating modes, electrodes 3, 5, 6, 11, 12, 14, and 15 are electrically connected to connection terminals 16, 17, and 18, respectively. A diaphragm 3 or diaphragm electrode 5 is connected to the first connection terminal 16. At least one first reference electrode 11 is connected to the second connection terminal 17. A counter electrode and at least one second reference electrode 12 are connected to the third connection terminal 18. Connection terminals 16, 17, and 18 can be connected, for example, via... Figure 1 The circuitry not shown corresponds to the desired operating mode and is in Figure 1 The control device and analysis processing circuit, which are not shown, are electrically connected and configured to controllably switch between the operating modes of the pressure sensor.

[0036] Figure 2 The electrical interconnections of the micromechanical sensor element 1 are schematically illustrated in a first operating mode. The first operating mode may, for example, be associated with a defined first measurement pressure range, such as a pressure range in the range of 300 to 1100 mBar; however, this is not required. The pressure values ​​and pressure ranges described within the scope of this specification should be understood as exemplary values ​​only.

[0037] In the first operating mode, a supply voltage, for example provided by the control device 20, can be applied between the diaphragm electrode 5 and at least one first reference electrode 11 via a first connection terminal 16 and a second connection terminal 17, while a tap 19 is constructed between the counter electrode 6 and at least one second reference electrode, in which a first measuring capacitor 7 and a reference capacitor 10 are interconnected. The tap 19 at the half-bridge is connected to a third connection terminal 18. The micromechanical sensor element 1 can be read through the third connection terminal 18.

[0038] Figure 3 A schematic cross-sectional view illustrating the pressure sensor during operation in the second operating mode. Figure 1 The micromechanical sensor element 1. A second operating mode may be configured, for example, to a defined second measurement pressure range, such as a high-pressure range, for example, a pressure range above 1100 mBar. However, this is not mandatory.

[0039] In the second operating mode, the diaphragm electrode 5, the counter electrode 6, and the reference electrodes 11 and 12 are interconnected such that the diaphragm electrode 5, together with at least one first reference electrode 11, forms a second measuring capacitance 21 for detecting the second measuring pressure. Here, at least one section of the diaphragm electrode 5, together with the first reference electrode 11, forms the second measuring capacitance 21. For example, a section of the diaphragm electrode 5 within the flexible region 8 of the diaphragm 3 (which, in one variation, may be a section of the diaphragm 3) can particularly form the second measuring capacitance 21 together with the first reference electrode 11, as in... Figure 3 As exemplarily shown in the example. In the case of another reference capacitor 13 Figure 3 In an exemplary embodiment of the micromechanical sensor element 1, the diaphragm electrode 5 also forms a second measurement capacitance 21 with another first reference electrode 14. In this case, the capacitance indicated between the diaphragm 3 and the reference electrodes 11, 14 corresponds to half of the total capacitance formed by the second measurement capacitance 21.

[0040] In the second operating mode, the supply voltage may be applied, for example, to the diaphragm electrode 5 and the counter electrode 6 or to the first connection terminal 16 and the third connection terminal 18, while at least one first reference electrode 11 and optionally another first reference electrode 14 act as a measurement tap or are electrically connected to the second connection terminal 17.

[0041] The diaphragm 3 and the counter electrode 6 can be designed and arranged such that the first measuring capacitor 7 is related to the measuring pressure in the first operating mode and independent of the measuring pressure in the second operating mode. In the second operating mode, the diaphragm 3 and at least one first reference electrode 11 can be designed and arranged such that the second measuring capacitor 21 is related to the measuring pressure in the second operating mode. Thus, there is a limitation on the measuring pressure range in the first operating mode, for example, the high-resolution low-pressure measuring range of the micromechanical sensor element 1.

[0042] This can be achieved in the micromechanical sensor element 1, for example, by shorting the diaphragm electrode 5 and the counter electrode 6 to each other. One possibility is that the ambient pressure is increased in such a way that the diaphragm is deflected to the point that the diaphragm electrode 5 contacts the counter electrode 6. Figure 3 The bending of diaphragm 3 is shown, shorting diaphragm electrode 5 to counter electrode 6. The first measuring capacitance 21 is thus independent of the measured pressure. Since diaphragm 3 remains pressure-sensitive despite the shorting, the second measuring capacitance 21 can be considered for measuring ambient pressure within the range of the second operating mode. By using the second measuring capacitance 21 in the second operating mode, the measurement range of the pressure sensor can be extended, even though the sensitivity is lower in the second measuring pressure range, for example, compared to the first measuring pressure range, but the accuracy requirements in the high-pressure range are also significantly lower.

[0043] In the second operating mode, the diaphragm 3 and at least one first reference electrode 11 can also be designed and arranged such that the second measuring capacitance 21 is related to the measuring pressure in the second operating mode, and there is no short circuit between the diaphragm electrode 5 and the counter electrode 6. For example, it may be sufficient for the diaphragm electrode 5 to simply rest against the counter electrode 6 without any electrical short circuit. To avoid short circuits, the diaphragm electrode 5 and / or the counter electrode 6 can be coated with an insulating material.

[0044] The short circuit or support of the diaphragm electrode 5 and the counter electrode 6, or the short circuit or support of the diaphragm electrode 5 at the counter electrode 6, can be determined, for example, by analyzing and processing the measurement signal. Generally, the short circuit or support of the electrodes 5 and 6 of the first measuring capacitance can be accurately determined by means of an additional mechanism, such as by means of the closure of the electrical contacts, so that the transition region can be accurately determined and thus support the analysis and processing circuitry. Alternatively, the transition to short circuit or support can also be detected by describing the short circuit state or support state. For this purpose, for example, calibration can be performed before the pressure sensor is put into operation to determine the relationship between ambient pressure and parameters such as temperature and air humidity, thereby describing the pressure range in which a short circuit occurs in the micromechanical sensor element 1, or the pressure range in which the diaphragm electrode 5 is supported at the counter electrode 6.

[0045] Figure 4 The schematic diagram shows the electrical interconnection of the second measuring capacitor 21 of the micromechanical sensor element 1 in the second operating mode.

[0046] exist Figure 4 The second measuring capacitor 21 shown is connected to the first connection terminal 16 and to the second connection terminal 17. In the second operating mode, for example, a supply voltage can be applied to the first connection terminal 16, and the second measuring capacitor 21 can be connected to the analysis and processing circuit via the second connection terminal.

[0047] Figure 4 Additionally, in the second operating mode, the second measuring capacitor 21 is interconnected with at least one high-voltage reference capacitor 22 in the second bridge circuit. The high-voltage reference capacitor 22 provides the advantages mentioned above. The high-voltage reference capacitor 22 can be used not only as a component of the micromechanical sensor element 1 but also as part of the pressure sensor's application-specific integrated circuit (ASIC). However, the high-voltage reference capacitor 22 can also be omitted, in which case the third connection terminal 18 is also omitted.

[0048] Figure 5 An exemplary pressure sensor 23 according to one possible implementation is schematically shown. The pressure sensor 23 has a micromechanical sensor element 1, and in the pressure sensor 23... Figure 5The variant shown includes a control device 20, a circuit device 24, and an analysis and processing device 25.

[0049] Circuit device 24 is configured to switch between operating modes of pressure sensor 23, for example, based on a first measured pressure detected by means of a first measuring capacitor 7 and / or a second measured pressure detected by means of a second measuring capacitor 21. Circuit device 24 may involve multiple switches, which may be configured as a multiplexer. In the first operating mode, the first and second connection terminals 16, 17 are connected to control device 20, and the third connection terminal 18 is connected to analysis and processing circuit 25. In the second operating mode, the first connection terminal 16 and the third connection terminal 18 are connected to control device 20, and the second connection terminal 17 is connected to analysis and processing circuit 25. Circuit device 24 may be configured to switch between operating modes of pressure sensor 23 at predefined time intervals.

[0050] For example, control device 20 may be configured to provide a periodic signal, such as a square wave signal, as a supply voltage. The supply voltage is fed via circuitry 24, corresponding to the operating mode, via first and second connections 16, 17, or via first connection 16 and third connection 18. Analysis and processing circuitry 25 may have an amplifier and / or an analog-to-digital converter. Analysis and processing circuitry 25 is configured to detect, analyze, and process the output voltage and provide an analog or digital measurement value based on the first measuring capacitor 7 or the second measuring capacitor 21.

[0051] Pressure sensor 23 is not limited to Figures 1 to 5 The topology shown is shown. Figure 6 The schematic diagram illustrates an assembly of an exemplary pressure sensor 23 having a micromechanical sensor element 1 according to another embodiment, the micromechanical sensor element 1 having a full-bridge circuit in a first operating mode.

[0052] The pressure sensor 23 includes a micromechanical sensor element 1 having at least two sensor structures 26 and 27, each having a pressure-sensitive diaphragm 3 spanning a common cavity 4 in the substrate material 2. Each sensor structure 26 and 27 is equipped with at least one first measuring capacitor 7 and 28 and reference capacitors 10 and 29, the at least one first measuring capacitor being used to detect a first measuring pressure. In a first operating mode, according to... Figure 6 The first measuring capacitors 7 and 28 and the reference capacitors 10 and 29 of at least two sensor structures 26 and 27 are interconnected in the first full-bridge circuit, thereby enabling differential detection of the first measuring pressure. Each sensor structure 26 and 27 forms a half-bridge. It is advantageous to implement the full-bridge circuit compactly in the pressure sensor 23, rather than as two separate half-bridge circuits.

[0053] In the first operating mode, such as in Figure 6 As exemplarily shown, the second sensor structure 27 can be connected to the control device 20 via the fourth connection terminal 30 and the fifth connection terminal 31, while the first sensor structure 26 is connected to the control device 20 via the first and second connection terminals 16 and 17. Another tap 32 is constructed between the counter electrode 6 and the second reference electrode 12 of the second sensor structure 27, and in this case, this other tap is connected to the analysis and processing circuit 25 (not shown) via the sixth connection terminal 33 of the second sensor structure 27. The first sensor structure 26 is connected to the analysis and processing circuit 25 via the third connection terminal 18. In this example, the two first measuring capacitors 7 and 28 are driven in opposite phase. The two first measuring capacitors can also be driven in phase—in this case, with… Figure 6 Compared to the previous arrangement, the first measuring capacitor 28 and the reference capacitor 29 of the second sensor structure 27 will be interchanged.

[0054] Interconnection, especially interconnection with control device 20, can here, for example, be achieved according to... Figure 5 The circuit device 24 is used to implement this.

[0055] Figure 7 The schematic diagram illustrates an exemplary electrical interconnection of the second measuring capacitors 21, 34 of the micromechanical sensor element 1 having two sensor structures 26, 27 in the second operating mode.

[0056] In the second operating mode, the diaphragm electrode 5, counter electrode 6, and reference electrode of each of at least two sensor structures 26 and 27 are interconnected such that the diaphragm electrode 5, together with at least one reference electrode 11, respectively forms second measuring capacitors 21 and 34 for detecting the second measuring pressure. This results in two capacitors, such as high-voltage capacitors, which can be differentially read. Figure 7 The second measuring capacitors 21 and 34 are exemplary connected individually and at different terminals to the control device 20 and individually to the analysis and processing circuit 25; however, this is not mandatory. For simplicity, circuit device 24 is not shown. Figure 7 As shown in the image.

[0057] As in Figure 4 As shown in the embodiment, in this case, in the second operating mode, the second measuring capacitors 21 and 34 can also be interconnected with at least one high-voltage reference capacitor 22 in the second bridge circuit, thereby producing a differentially read full bridge. Figure 8This is illustrated schematically as an example interconnection for a micromechanical sensor element 1 having two sensor structures 26, 27 in the second operating mode. Sensor structures 26, 27 are respectively connected to a high-voltage reference capacitor 22 in a half-bridge circuit, wherein the half-bridge forms a second bridge circuit configured as a full-bridge circuit.

[0058] The second connection terminal 17 and the fifth connection terminal 31 are configured to read the output voltage in the second operating mode. For this purpose, the second connection terminal and the fifth connection terminal 34 are respectively connected to taps at the half-bridges between the sensor structures 26 and 27 and the high-voltage reference capacitor 22. For example, the taps at the half-bridges can be connected to the analysis and processing circuit 24. According to... Figure 9 In some embodiments, sensor structures 26 and 27 can be connected to a control device via their other connection terminals 16, 18, 30, and 33.

[0059] Figure 9 The diagram schematically illustrates method steps 36, 37, and 38 of a method 35 for operating a pressure sensor 23 according to one embodiment. In method 35, various operating modes of the pressure sensor 23 are assigned to defined pressure ranges.

[0060] In the first method step 36, the pressure to be measured is monitored by detecting and analyzing the first and / or second measured pressures. In the second method step 37, the current preferred operating mode of the pressure sensor 23 is identified based on the analysis of the detected measured pressures. Within the scope of the third method step 38, if the pressure sensor 23 is currently in an operating mode different from the preferred operating mode, it is switched to the current preferred operating mode. After switching to the current preferred operating mode, method steps 36, 37, and 38 can be repeated.

[0061] When a short circuit exists between the diaphragm electrode 5 and the counter electrode 6 of the first measuring capacitors 7, 28, the pressure sensor 23 can operate, for example, in a second operating mode. Switching between the first and second operating modes of the pressure sensor 23 can be performed, for example, based on the presence or absence of a short circuit between the diaphragm electrode 5 and the counter electrode 6 of the first measuring capacitors 7, 28. In method 35, the pressure sensor can be switched between its various operating modes, for example, at pre-given time intervals. The detected first or second measuring pressure can be analyzed in terms of functional monitoring of the pressure sensor 23 and / or reliability verification of the pressure measurement.

Claims

1. A pressure sensor (23), said pressure sensor comprising at least: A micromechanical sensor element (1) having at least one pressure-sensitive diaphragm (3) spanning a cavity (4) in a substrate material (2) and having a diaphragm electrode (5). A fixed counter electrode (6) is arranged in the cavity (4) and together with the diaphragm electrode (5) forms a first measuring capacitor (7), which is used to detect a first measuring pressure. A reference capacitor (10) is arranged within the cavity (4) and includes at least one fixed first reference electrode (11) and a second reference electrode (12). Its features are, The pressure sensor (23) is capable of operating in at least one first operating mode, in which the first measuring capacitor (7) and the reference capacitor (10) are interconnected in a first bridge circuit, and The pressure sensor (23) is capable of operating in at least one second operating mode, in which the diaphragm electrode (5), the counter electrode (6) and the reference electrode are interconnected, such that the diaphragm electrode (5) and the at least one first reference electrode (11) together form a second measuring capacitor (21), which is used to detect a second measuring pressure.

2. The pressure sensor (23) according to claim 1, characterized in that, The first operating mode is assigned to the first measurement pressure range and the second operating mode is assigned to the second measurement pressure range.

3. The pressure sensor (23) according to any one of claims 1 or 2, characterized in that, A circuit device (24) is provided for controllably switching between the operating modes of the pressure sensor (23).

4. The pressure sensor (23) according to claim 3, characterized in that, The circuit device (24) is configured to switch between the operating modes of the pressure sensor (23) based on a detected first measured pressure and / or a detected second measured pressure.

5. The pressure sensor (23) according to claim 3, characterized in that, The circuit device (24) is configured to switch between operating modes of the pressure sensor (23) at pre-given time intervals.

6. The pressure sensor (23) according to any one of claims 1 or 2, characterized in that, The diaphragm (3) and the counter electrode (6) are designed and arranged such that the first measuring capacitor (7) is related to the measuring pressure in the first operating mode and is independent of the measuring pressure in the second operating mode, and the diaphragm (3) and the at least one first reference electrode (11) are designed and arranged such that the second measuring capacitor (21) is related to the measuring pressure in the second operating mode.

7. The pressure sensor (23) according to any one of claims 1 or 2, characterized in that, In the first operating mode, a supply voltage is applied between the diaphragm electrode (5) and the at least one first reference electrode (11), and a tap (19) of the bridge circuit is constructed between the counter electrode (6) and the at least one second reference electrode (12). In the second operating mode, the supply voltage is applied at the diaphragm electrode (5) and the counter electrode (6), and the at least one first reference electrode (11) acts as a measurement tap.

8. The pressure sensor (23) according to claim 7, characterized in that, In the second operating mode, the counter electrode (6) and the at least one second reference electrode (12) are short-circuited.

9. The pressure sensor (23) according to any one of claims 1 or 2, characterized in that, In the second operating mode, the second measuring capacitor (21) is interconnected with at least one high-voltage reference capacitor (22) in the second bridge circuit.

10. The pressure sensor (23) according to any one of claims 1 or 2, characterized in that, The micromechanical sensor element (1) includes at least two sensor structures (26, 27), each of which has a pressure-sensitive diaphragm (3) that spans a cavity (4) in the substrate material (2). Each sensor structure (26, 27) is equipped with at least one first measuring capacitor (7, 28) and a reference capacitor, wherein the at least one first measuring capacitor is used to detect a first measuring pressure. In the first operating mode, the first measuring capacitor (7, 28) and the reference capacitor of the at least two sensor structures (26, 27) are interconnected in the first full-bridge circuit, thereby enabling differential detection of the first measuring pressure, and In the second operating mode, the diaphragm electrode (5), counter electrode (6) and reference electrode of each of the at least two sensor structures (26, 27) are interconnected, such that the diaphragm electrode (5) and the at least one first reference electrode (11) respectively form a second measuring capacitor, which is used to detect the second measuring pressure.

11. A method (35) for operating a pressure sensor (23) according to any one of claims 1 to 10, wherein, The various operating modes of the pressure sensor (23) are assigned to a defined pressure range. The characteristic is that the pressure to be detected is monitored by detecting and analyzing the first measured pressure and / or the second measured pressure, the current preferred operating mode of the pressure sensor (23) is identified based on the analysis and processing of the detected measured pressure, and the pressure sensor (23) is switched to the current preferred operating mode when the pressure sensor (23) is currently in an operating mode that is different from the preferred operating mode.

12. The method (35) according to claim 11, characterized in that, When there is a short circuit between the diaphragm electrode (5) and the counter electrode (6) of the first measuring capacitor (7), the pressure sensor (23) is operated in the second operating mode; the switching between the first and second operating modes of the pressure sensor (23) is performed according to whether there is a short circuit between the diaphragm electrode (5) and the counter electrode (6) of the first measuring capacitor (7).

13. The method (35) according to any one of claims 11 or 12, characterized in that, The pressure sensor (23) is switched between various operating modes at pre-given time intervals, and the first or second measured pressure subsequently detected is analyzed and processed in terms of functional monitoring and / or reliability verification of pressure measurements of the pressure sensor (23).

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