DE102022203983A1 - Pressure sensor and method for operating a pressure sensor - Google Patents

Abstract

A pressure sensor comprises a membrane which is designed to be deflected depending on a pressure to be determined. The pressure sensor further comprises a capacitive measuring device with a plurality of measuring capacitances connected to a Wheatstone measuring bridge, the measuring device being arranged in such a way that a bridge voltage of the Wheatstone measuring bridge depends on the deflection of the membrane, and the measuring device being designed to do so as a function to output a measurement signal from the bridge voltage of the Wheatstone measuring bridge to determine the pressure. The pressure sensor further comprises at least one compensation capacitance, which is connected or can be switched in parallel to at least one of the measuring capacitances in order to reduce the temperature dependence of the measurement signal.

Description

The present invention relates to a pressure sensor and a method for operating a pressure sensor.

State of the art

Miniaturized sensors based on MEMS (microelectromechanical systems) technology are known for pressure measurement. For this purpose, a membrane can be clamped into a frame. The pressure difference between an area above the membrane and an area below the membrane (e.g. in a cavern) leads to a deflection of the membrane. Capacitive pressure sensors convert this deflection into an electrical signal by changing the distance between the plates between two electrodes.

Even if the temperature cross-dependence of capacitive pressure sensors is much lower than that of piezoresistive pressure sensors, there still remains a temperature dependence of the sensor signal. One reason is that the modulus of elasticity (modulus of elasticity) of the membrane material is temperature-dependent. The same applies to the internal cavern pressure. Furthermore, the capacitive pressure sensor can interact with the construction and connection technology used, which can also lead to temperature dependencies.

From the DE 10 2018 222 712 A1 A pressure sensor is known whose membrane consists of only one material in order to reduce temperature effects.

Temperature compensation structures can be integrated into the pressure sensor element or designed as an external circuit consisting of corresponding resistance networks. Temperature-dependent resistors are connected accordingly in a Wheatstone measuring bridge. In the US 5,391,951 A Temperature compensation is achieved by selecting the resistance structures during calibration.

For capacitive pressure sensors, possible temperature compensation is possible via an RC network in the US 4,807,477 A described.

Disclosure of the invention

The invention provides a pressure sensor and a method for operating a pressure sensor with the features of the independent claims.

Preferred embodiments are the subject of the respective subclaims.

According to a first aspect, the invention therefore relates to a pressure sensor with a membrane which is designed to be deflected depending on a pressure to be determined. The pressure sensor further comprises a capacitive measuring device with a plurality of measuring capacitances connected to a Wheatstone measuring bridge, the measuring device being arranged in such a way that a bridge voltage of the Wheatstone measuring bridge depends on the deflection of the membrane, and the measuring device being designed to do so as a function to output a measurement signal from the bridge voltage of the Wheatstone measuring bridge to determine the pressure. The pressure sensor further comprises at least one compensation capacitance, which is connected or can be switched in parallel to at least one of the measuring capacitances in order to reduce the temperature dependence of the measurement signal.

According to a second aspect, the invention relates to a method for operating a pressure sensor, wherein the pressure sensor comprises a membrane which is deflected depending on a pressure to be determined, wherein the pressure sensor comprises a capacitive measuring device with a plurality of measuring capacitances connected to a Wheatstone measuring bridge , wherein the measuring device is arranged such that a bridge voltage of the Wheatstone measuring bridge depends on the deflection of the membrane, wherein the measuring device outputs a measuring signal for determining the pressure depending on the bridge voltage of the Wheatstone measuring bridge, and wherein the pressure sensor has at least one compensation capacity , which can be connected in parallel to at least one of the measuring capacitances in order to reduce the temperature dependence of the measuring signal. A temperature of the pressure sensor is determined. Furthermore, the at least one compensation capacitance is switched on or off in parallel with at least one of the measuring capacitances depending on the determined temperature of the pressure sensor.

Advantages of the invention

The invention makes it possible to further reduce the temperature dependence when measuring pressures. For this purpose, compensation capacitances are provided, which are understood to be capacitances (e.g. capacitor structures) which reduce or preferably eliminate the overall temperature dependence of the measurement due to their own specifically selected temperature dependence.

Preferably, the temperature dependence of the pressure sensor can be reduced to such an extent that a single-temperature adjustment is sufficient to achieve sufficient performance.

According to a further embodiment of the pressure sensor, the at least one compensation capacitance comprises a dielectric with temperature-dependent permittivity.

According to a further embodiment of the pressure sensor, a material and/or dimensions of the dielectric are selected such that the temperature dependence of the measurement signal is reduced due to a temperature dependence of a capacitance of the compensation capacitance. In particular, pressure-dependent contributions can be compensated.

According to a further embodiment of the pressure sensor, the measuring device has a cavity in which a reference pressure is formed, a value of the reference pressure being selected such that the temperature dependence of the measurement signal is further reduced. In particular, print-independent contributions can be compensated.

According to a further embodiment of the pressure sensor, the membrane and the at least one compensation capacitance are formed on a common substrate. The pressure sensor can, for example, comprise a MEMS structure with the common substrate and the components arranged thereon. The pressure sensor also includes an evaluation circuit, such as an application-specific integrated circuit (ASIC). The compensation capacities are applied to the MEMS structure, with the advantage of a very good temperature connection to the element to be compensated for static, but especially dynamic applications or temperature changes. Temperature gradients within the packaged sensor, i.e. with MEMS and ASIC and possibly other components, then play no role or do not worsen performance.

If the compensation capacitances are applied to the MEMS, they can be connected to metal conductor tracks in a metal level. In order to obtain the optimal capacitance size for optimal compensation, the metal conductor tracks can be cut, for example, using a laser ablation process.

According to a further embodiment, the pressure sensor comprises an evaluation device, such as an ASIC, which is designed to determine the pressure to be measured from the measurement signal, with at least one of the at least one compensation capacitance being integrated into the evaluation device. The compensation capacities can therefore be switched on externally. This makes it possible, for example, to react to a fluctuation in the cavern pressure and the analog temperature compensation can be trimmed individually for each pressure sensor.

The compensation capacities can be optionally switched on in the evaluation device, e.g. in the event of rapid temperature changes in the system, in which temperature gradients between a temperature sensor and the MEMS lead to measurement errors. Furthermore, the compensation capacitances can be separated by the evaluation device in order to reduce the basic capacity of the overall circuit, which leads to lower noise behavior.

If the compensation capacitances are arranged on the ASIC, they can be connected digitally, e.g. through transmission gates, in parallel so that the optimal capacitance size results in optimal compensation.

According to a further embodiment of the pressure sensor, a temperature-dependent compensation capacitance can be applied to the MEMS and a further temperature-dependent compensation capacitance, but with a different temperature coefficient, in the evaluation circuit, in particular in the ASIC. This can be implemented as a half or full bridge.

According to a further embodiment, the pressure sensor comprises a control device which is designed to switch the at least one compensation capacitance on or off in parallel to at least one of the measuring capacitances depending on a temperature of the pressure sensor. By switching off the at least one compensation capacitance, the noise of the measurements can be reduced. Conversely, by connecting the at least one compensation capacitor, a high temperature stability of the pressure measurement value can be achieved.

According to a further embodiment of the pressure sensor, there are several capacity structures to choose from and the ideal capacity structure can be selected accordingly during the final adjustment of the component.

According to a further embodiment of the pressure sensor, the control device is designed to cyclically (e.g. periodically) switch the at least one compensation capacitance on or off in parallel with at least one of the measuring capacitances. Cyclic switching on and off is particularly advantageous if low noise and high temperature stability are desired. During the short period of switching, neither pressure nor temperature generally changes, so that the lower-noise measured value can be corrected without compensation capacities based on the temperature-stable behavior with compensation capacities.

According to a further embodiment of the pressure sensor, the measuring capacities include two pressure-dependent measuring capacities and two pressure-independent measuring capacities.

According to a further embodiment of the pressure sensor, the Wheatstone measuring bridge is a half bridge. In this case, the number of measuring capacitances can be equal to two. The Wheatstone measuring bridge is preferably a full bridge. In this case, four measuring capacities are provided.

Further advantages, features and details of the invention emerge from the following description, in which various exemplary embodiments are described in detail with reference to the drawing.

Brief description of the drawings

• 1 ein schematisches Blockdiagramm eines Drucksensors gemäß einer Ausführungsform der Erfindung;
• 2 ein schematisches Schaltbild zur Verwendung in einem Drucksensor gemäß einer Ausführungsform der Erfindung;
• 3 eine schematische Querschnittsansicht eines Drucksensors gemäß einer Ausführungsform der Erfindung;
• 4 eine weitere schematische Querschnittsansicht des in 3 gezeigten Drucksensors;
• 5 eine schematische Draufsicht auf eine Kompensationskapazität zur Verwendung in einem Drucksensor gemäß einer Ausführungsform der Erfindung;
• 6 eine schematische Querschnittsansicht von Kompensationskapazitäten gemäß einer Ausführungsform der Erfindung;
• 7 eine schematische Querschnittsansicht von Kompensationskapazitäten gemäß einer weiteren Ausführungsform der Erfindung;
• 8 eine schematische Querschnittsansicht eines Drucksensors gemäß einer Ausführungsform der Erfindung; und
• 9 ein Flussdiagramm eines Verfahrens zum Betreiben eines Drucksensors gemäß einer Ausdrucksform der Erfindung.

Show it:

• 1 a schematic block diagram of a pressure sensor according to an embodiment of the invention;
• 2 a schematic circuit diagram for use in a pressure sensor according to an embodiment of the invention;
• 3 a schematic cross-sectional view of a pressure sensor according to an embodiment of the invention;
• 4 another schematic cross-sectional view of the in 3 pressure sensor shown;
• 5 a schematic top view of a compensation capacitance for use in a pressure sensor according to an embodiment of the invention;
• 6 a schematic cross-sectional view of compensation capacitances according to an embodiment of the invention;
• 7 a schematic cross-sectional view of compensation capacitances according to a further embodiment of the invention;
• 8th a schematic cross-sectional view of a pressure sensor according to an embodiment of the invention; and
• 9 a flowchart of a method for operating a pressure sensor according to an embodiment of the invention.

In all figures, identical or functionally identical elements and devices are provided with the same reference numerals. The numbering of procedural steps is for clarity and is generally not intended to imply a specific chronological order. In particular, several process steps can be carried out simultaneously.

Description of the exemplary embodiments

1 shows a schematic block diagram of a pressure sensor 1. The pressure sensor 1 comprises a membrane 2, which is deflected depending on a pressure to be determined. For this purpose, a cavern can be provided on one of the sides of the membrane 2, in which a reference pressure is formed.

The pressure sensor 1 further comprises a capacitive measuring device 3 with a plurality of measuring capacitances 41 to 4n connected to a Wheatstone measuring bridge 4, where n denotes the number of measuring capacitances 41 to 4n. For example, n = 4 and the Wheatstone measuring bridge 4 is a full bridge. The measuring capacities 41 to 4n can include two pressure-dependent measuring capacities (actuator capacities) and two pressure-independent measuring capacities (reference capacities). Alternatively, n = 2 and the Wheatstone measuring bridge 4 is a half bridge.

The measuring capacitances 41 to 4n are arranged on or near the membrane 2, so that a bridge voltage of the Wheatstone measuring bridge 4 depends on the deflection of the membrane 2.

The measuring device 3 generates a measuring signal for determining the pressure depending on the bridge voltage of the Wheatstone measuring bridge 4 and outputs it. For example, the measuring device 3 can output the value of the bridge voltage itself as a measurement signal.

The membrane 2 and the capacitive measuring device 3 can be part of a MEMS component.

The pressure sensor 1 further comprises at least one compensation capacitance 51 to 5m, where m denotes the number of compensation capacitances 51 to 5m. In one embodiment, exactly one compensation capacity is provided, i.e. H. m = 1 applies. The compensation capacities 51 to 5m can be individual capacities or they can be a corresponding capacity network.

The compensation capacitances 51 to 5m are connected in parallel to at least one of the measuring capacitances 41 to 4n. According to a further embodiment, the compensation capacities 51 to 5m can be switched on.

The at least one compensation capacitance 51 to 5m comprises electrically conductive components with a dielectric formed therebetween, which has a temperature-dependent permittivity. A material and/or dimensions of the dielectric are selected such that the temperature dependence of the measurement signal is reduced due to a temperature dependence of a capacitance of the compensation capacitance 51 to 5m. This is explained in more detail below.

The temperature dependence per pressure change can be described by the following parameter rawTCO: $$\text{rawTCO}=\frac{\partial \left(\text{DC}\right)\text{/}\partial \text{T}}{\partial \left(\text{DC}\right)\text{/}\partial \text{p}}$$

Here, for a full bridge consisting of two half-bridges, the size dC denotes the difference in the capacitance values of the two half-bridges.

In the case of a plate capacitor as a compensation capacitance of 51 to 5m, the ideal change in capacitance of the plate capacitor of area A with an initial gap d and a pressure-dependent deflection k(T) p at the external pressure p results as follows: $${\text{C}}_{\text{ideal}}=\frac{{\mathrm{\epsilon }}_0\text{A}}{\text{d}-\text{k}\left(\text{T}\right)\cdot \left(p-p_{cav}\right)}$$

p _cav denotes the cavern pressure (reference pressure) and C _ideal denotes the temperature-dependent capacity.

The deflectability k(T) is given by the following formula depending on the membrane geometry c, the membrane thickness t and the modulus of elasticity E: $$\text{k}\left(\text{T}\right)=\frac{c}{\text{E}\left(\text{T}\right){\text{<figure-callout id="3" label="t" filenames="DE102022203983A1\_0015.png" state="{{state}}">t</figure-callout>}}^3}$$

The sensitivity is calculated as: $$sensitivity=\frac{\partial C_{ideal}}{\partial p}=\frac{k\left(T\right)\cdot {\epsilon }_{0}A}{{\left(d-k\left(T\right)\cdot p\right)}^2}$$

This results in the temperature dependence per pressure using the ideal gas equation pV = nRT: $$\text{rawTCO}=-\frac{\partial \text{E}/\partial \text{T}}{\text{E}\left(\text{T}\right)}p-\frac{p_{cav}}{T}+\frac{\partial \left({\text{C}}_{\text{art}\text{, Diel}}-{\text{C}}_{\text{ref}\text{, Diel}}\right)/\partial \text{T}}{\text{sensitivity}}$$

C _act,diel and C _ref,diel denote the capacitance values of the dielectrics of the pressure-dependent measuring capacities (actuator capacities) and pressure-independent measuring capacities (reference capacities), respectively.

By rearranging you get: $$rawTCO=-\frac{\partial E/\partial T}{E\left(T\right)}p-\frac{p_{cav}}{T}-\frac{\partial \Delta C_{cOmpensate}/\partial T}{k\left(T\right)\cdot {\epsilon }_{0}A}\cdot {\left(d-k\left(T\right)\cdot p\right)}^2$$

For small pressures the p ² term can be neglected, ie one linearizes over the pressure p. Then you get: $$rawTCO\approx -\frac{\partial E/\partial T}{E\left(T\right)}p-\frac{p_{cav}}{T}-\frac{\partial \Delta C_{cOmpensate}/\partial T}{k\left(T\right)\cdot {\epsilon }_{0}A}\cdot {\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="DE102022203983A1\_0015.png"\; state="\{\{state\}\}">d</figure-callout>}}^2+\frac{\partial \Delta C_{cOmpensate}/\partial T}{k\left(T\right)\cdot {\epsilon }_{0}A}\cdot 2\cdot d\cdot k\left(T\right)\cdot p$$

Changing to the power of the pressure p results in: $$rawTCO\approx \left[2\cdot \frac{\partial \Delta C_{cOmpensate}/\partial T}{C_{sens}\left(0kPa\right)}-\frac{\partial E/\partial T}{E\left(T\right)}\right]p-\frac{p_{cav}}{T}-\frac{\partial \Delta C_{cOmpensate}/\partial T}{k\left(T\right)\cdot {\epsilon }_{0}A}\cdot {\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="DE102022203983A1\_0015.png"\; state="\{\{state\}\}">d</figure-callout>}}^2$$

sich gerade derart einstellt, dass die Temperaturabhängigkeit des Messsignals druckunabhängig wird. Dies erreicht man durch folgende Wahl: $$\partial \Delta C_{compensate}/\partial T=\frac{C_{sens}\left(0kPa\right)}{2}\cdot \frac{\partial E/\partial T}{E\left(T\right)}$$

Material and dimensions of the dielectric of the compensation capacitances 51 to 5m can be selected such that temperature compensation $$\partial \Delta C_{cOmpensate}/\partial T$$

just happens in such a way that the temperature dependence of the measurement signal becomes pressure-independent. This can be achieved by choosing the following: $$\partial \Delta C_{cOmpensate}/\partial T=\frac{C_{sens}\left(0kPa\right)}{2}\cdot \frac{\partial E/\partial T}{E\left(T\right)}$$

wobei: $$p_{cav}=-1/2\cdot \frac{\frac{\partial E/\partial T}{E\left(T\right)}}{\frac{k\left(T\right)}{d}}\cdot T$$

Based on the then specified properties of the temperature compensation, the required cavern pressure can be calculated so that the pressure-constant term of the temperature dependence also disappears: $$\frac{p_{cav}}{T}=-\frac{\partial \Delta C_{cOmpensate}/\partial T}{k\left(T\right)\cdot C_{sens}\left(0kPa\right)}\cdot d=\frac{\frac{\partial E/\partial T}{E\left(T\right)}}{2\cdot k\left(T\right)}\cdot d$$

where: $$p_{cav}=-1/2\cdot \frac{\frac{\partial E/\partial T}{E\left(T\right)}}{\frac{k\left(T\right)}{d}}\cdot T$$

For example, with a reduction in the elastic modulus of 0.1% per Kelvin, the membrane deflection normalized to the original gap of 1/50 kPa and 298 Kelvin for the cavern pressure results: $$0.5\cdot 0.1\text{\%K}\cdot \text{298K}\cdot \text{50 kPa}=\mathrm{8th}\text{kPa}$$

The relative capacity temperature variability results in: $$\frac{\partial \Delta C_{cOmpensate}/\partial T}{C_{sens}\left(0kPa\right)}=0.1\text{\%/}K\text{/2=0}\text{.05\%/}K$$

The pressure sensor 1 can thus be designed to be temperature-stable using the temperature compensation capacities 51 to 5m and by selecting the cavern pressure.

Inorganic insulators such as silicon nitride, silicon-rich nitride, aluminum nitride or titanium oxide can be used as temperature-dependent dielectrics. These materials can also be modified with other elements, such as: B, barium, strontium, lead or lanthanum. Zirconium titanium oxides in particular have advantageous temperature-dependent properties, since the permittivity of piezo or ferroelectrics changes significantly near the Curie temperature.

According to a further embodiment, the cavern pressure is initially specified, which results, for example, on average over the manufacturing process. The pressure sensor 1 can then be optimized for specific operating points by selecting suitable compensation capacities 51 to 5m, for example for room pressure at sea level.

The measurement signal is received by an evaluation device 6, for example an ASIC, which determines the pressure to be measured from the measurement signal.

According to one embodiment, at least one of the at least one compensation capacitance 51 to 5m is integrated into the evaluation device 6. Furthermore, at least one of the at least one compensation capacitance 51 to 5m can be integrated into the MEMS component. According to one embodiment, all compensation capacities 51 to 5m are integrated into the evaluation device 6. According to another embodiment, all compensation capacitances 51 to 5m are integrated into the MEMS component.

Furthermore, the pressure sensor 1 can include a control device 7, which cyclically switches on or off the at least one compensation capacitance 51 to 5m in parallel to at least one of the measuring capacitances 41 to 4n. The switching on or off can take place depending on a temperature or temperature change of the pressure sensor 1. For this purpose, a temperature sensor (not shown) in the pressure sensor 1 or in the vicinity of the pressure sensor can determine the temperature of the pressure sensor 1 and transmit it to the control device 7.

The control device 7 can be integrated into the evaluation device 6 or implemented by it, for example as an ASIC.

2 shows a schematic circuit diagram for use in a pressure sensor, in particular the one in 1 pressure sensor 1 shown. Accordingly, the measuring device comprises two pressure-dependent measuring capacitances C1 and C4, as well as two pressure-constant measuring capacitances C2 and C3, which can serve as reference capacitances. The measuring capacitances C1 to C4 are connected to form a full bridge. In parallel, capacitances for compensating for temperature dependence (compensation capacitances) C2T(T) and C3T(T) are provided, which are connected in parallel to the measuring capacitances C2 and C3, respectively. The compensation capacities are temperature dependent. The bridge voltage between S1 and S2 is read out.

C2T(T) and C3T(T) can also alternatively be arranged parallel to C1 and C2.

Despite different dielectric constants, the capacitances can be designed to have the same capacitance value, for example at 25°C, by adjusting the geometry.

This in 2 The circuit diagram shown can be understood as a connection of a pressure-sensitive capacitive full bridge with capacitances C1 to C4 and a temperature-sensitive capacitive full bridge with capacitances C2, C2T, C3, C3T. T1 and T2 designate the voltage supply for both full bridges, so that two bond pads on the MEMS can advantageously be saved and the chip area decreases.

3 shows a schematic cross-sectional view of a pressure sensor 1a, with a substrate 36 and a layer stack thereon with a first dielectric layer 35 and a second dielectric layer 34. The dielectric layers 34, 35 can be part of a compensation capacitance, with electrically conductive structures, not shown. Furthermore, two measuring electrodes 31, 33 of a reference capacitance are arranged on the layer stack. The electric field 32 and thus also the capacitance value between the electrodes 31, 33 is independent of the temperature T.

In further embodiments, more or fewer dielectric layers are provided.

4 shows another schematic cross-sectional view of the in 3 pressure sensor 1a shown, wherein a temperature-dependent stray field capacitance 41 is drawn through the dielectric layers 34, 35, which causes the temperature dependence of the capacitance value generated by the electric field 32 to be compensated.

5 shows a schematic top view of an exemplary compensation capacity for use in a pressure sensor, in particular one of the pressure sensors 1, 1a described above. The compensation capacitance has an interdigital structure, which enables a strong stray field between electrodes 51, 52 of the compensation capacitance through a dielectric 53 with temperature-dependent permittivity located between them.

An interdigital structure achieves a high gap area between the electrodes 51, 52, so that, as in 4 can be seen, a strong field 41 can form between the two electrodes 51, 52 through the dielectric 53 when both electrodes 51, 52 are set to different potentials.

6 shows a schematic cross-sectional view of compensation capacitances according to an embodiment of in 5 shown interdigital structure, with a dielectric layer 53, on which the electrodes 51, 52 are arranged, so that an air gap 61 extends between them, and an electric field 62 is formed primarily in the dielectric layer 53.

7 shows a schematic cross-sectional view of a compensation capacitance according to a further embodiment of in 5 shown interdigital structure, with a further dielectric layer 71 with temperature-dependent dielectric properties, so that an electric field 72 is formed between the electrodes 51, 52.

8th shows a schematic cross-sectional view of a pressure sensor 1b according to an embodiment of the invention. Instead of an interdigital structure, a plate capacitor with a conductive structural element 81 is used as a compensation capacitance. As a result, with a suitable layer thickness and the same required capacity, the area that the capacity requires can be reduced.

9 shows a flowchart of a method for operating a pressure sensor according to an embodiment of the invention.

The pressure sensor 1 can correspond to one of the pressure sensors 1, 1a, 1b described above. In particular, the pressure sensor 1, 1a, 1b comprises a membrane 2, which is deflected depending on a pressure to be determined.

The pressure sensor 1, 1a, 1b further comprises a capacitive measuring device 3 with a plurality of measuring capacitances 41 to 4n connected to a Wheatstone measuring bridge 4, the measuring device 3 being arranged in such a way that a bridge voltage of the Wheatstone measuring bridge 4 depends on the deflection of the membrane 2 depends. The measuring device 3 gives, depending on the bridge voltage of the Wheatstone Measuring bridge emits a measuring signal to determine the pressure. The pressure can be determined, for example, by an evaluation device 6 described above.

The pressure sensor 1, 1a, 1b further comprises at least one compensation capacitance 51 to 5n, which can be switched in parallel to at least one of the measuring capacitances 41 to 4n in order to reduce the temperature dependence of the measurement signal.

In a first method step S1, a temperature of the pressure sensor 1, 1a, 1b is determined. For this purpose, the pressure sensor 1, 1a, 1b can have a temperature sensor or can be arranged together with the temperature sensor. The temperature can optionally be compared with a previously measured temperature and a temperature difference can be calculated.

In a second method step S2, the at least one compensation capacitance is switched on or off in parallel with at least one of the measuring capacitances depending on the determined temperature of the pressure sensor 1, 1a, 1b or the temperature difference. This can be done, for example, by a control device 7, which can be the evaluation device 6 or which is integrated into the evaluation device 6. According to further embodiments, it can be provided that the pressure sensor 1, 1a, 1b is set externally in a specific mode, for example a mode in which switching is cyclically switched on or off.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102018222712 A1 [0004]
• US 5391951 A [0005]
• US 4807477 A [0006]

Claims (10)

Pressure sensor (1; 1a; 1b), with: a membrane (2), which is designed to be deflected depending on a pressure to be determined; a capacitive measuring device (3) with a plurality of measuring capacitances (41-4n) connected to a Wheatstone measuring bridge (4), the measuring device (3) being arranged in such a way that a bridge voltage of the Wheatstone measuring bridge (4) depends on the deflection of the Membrane (2) depends, and wherein the measuring device (3) is designed to output a measuring signal for determining the pressure depending on the bridge voltage of the Wheatstone measuring bridge (4); and with at least one compensation capacitance (51-5m), which is connected or switchable in parallel to at least one of the measuring capacitances (41-4n) in order to reduce the temperature dependence of the measurement signal. Pressure sensor (1; 1a; 1b). Claim 1 , wherein the at least one compensation capacitance (51-5m) comprises a dielectric with temperature-dependent permittivity. Pressure sensor (1; 1a; 1b). Claim 2 , wherein a material and/or dimensions of the dielectric are selected such that the temperature dependence of the measurement signal is reduced using a temperature dependence of a capacitance of the compensation capacitance (51-5m). Pressure sensor (1; 1a; 1b) according to one of the preceding claims, wherein the measuring device (3) has a cavern in which a reference pressure is formed, a value of the reference pressure being selected such that the temperature dependence of the measurement signal is further reduced. Pressure sensor (1; 1a; 1b) according to one of the preceding claims, wherein the membrane (2) and the at least one compensation capacitance (51-5m) are formed on a common substrate. Pressure sensor (1; 1a; 1b) according to one of the preceding claims, with an evaluation device (6) which is designed to determine the pressure to be measured from the measurement signal, with at least one of the at least one compensation capacitance (51-5m) in the Evaluation device is integrated. Pressure sensor (1; 1a; 1b) according to one of the preceding claims, with a control device (7) which is designed to control the at least one compensation capacity (51-5m) depending on a temperature of the pressure sensor (1; 1a; 1b) in parallel to switch on or off at least one of the measuring capacitances (41-4n). Pressure sensor (1; 1a; 1b). Claim 7 , wherein the control device (7) is designed to cyclically switch on or off the at least one compensation capacitance (51-5m) in parallel to at least one of the measuring capacitances (41-4n). Pressure sensor (1; 1a; 1b) according to one of the preceding claims, wherein the measuring capacities (41-4n) comprise two pressure-dependent measuring capacities (41-4n) and two pressure-independent measuring capacities (41-4n). Method for operating a pressure sensor (1; 1a; 1b), wherein the pressure sensor (1; 1a; 1b) comprises a membrane (2) which is deflected depending on a pressure to be determined, wherein the pressure sensor (1; 1a; 1b ) comprises a capacitive measuring device (3) with a plurality of measuring capacitances (41-4n) connected to a Wheatstone measuring bridge (4), the measuring device (3) being arranged in such a way that a bridge voltage of the Wheatstone measuring bridge (4) depends on the Deflection of the membrane (2), the measuring device (3) outputting a measuring signal to determine the pressure depending on the bridge voltage of the Wheatstone measuring bridge (4), and the pressure sensor (1; 1a; 1b) having at least one compensation capacitance (51 -5m), which can be connected in parallel to at least one of the measuring capacitances (41-4n) in order to reduce a temperature dependence of the measuring signal, the method having the following steps: determining (S1) a temperature of the pressure sensor (1; 1a; 1b); and switching on or off (S2) the at least one compensation capacitance (51-5m) in parallel with at least one of the measuring capacitances (41-4n), depending on the determined temperature of the pressure sensor (1; 1a; 1b).

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