Capacitive pressure sensor, and pressure measurement device

Abstract

The present application relates to the technical field of pressure sensors. Disclosed are a capacitive pressure sensor, and a pressure measurement device. The capacitive pressure sensor mainly comprises: a fixed electrode layer, an insulating layer and a variable electrode layer, wherein the insulating layer is arranged at the upper end of the fixed electrode layer, and the upper surface of the insulating layer is provided with a groove; the variable electrode layer seals an opening of the groove to form a sealed cavity, and the fixed electrode layer and the variable electrode layer form a variable capacitor; and a response of the variable electrode layer and the sealed cavity to an air pressure is determined on the basis of sensitivity per unit area, a degree of deformation of the variable electrode layer is determined on the basis of the response of the variable electrode layer and the sealed cavity to the air pressure, a variation in capacitance readings is determined on the basis of the degree of deformation of the variable electrode layer, and an air pressure value is determined on the basis of the variation in capacitance readings. With regard to the capacitive pressure sensor provided in the present application, the performance of the capacitive pressure sensor is dominated by an equivalent spring coefficient of a sealed cavity, improving both the sensitivity and linear measurement range of the capacitive pressure sensor.

Description

Capacitive pressure sensor and pressure detection equipment

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411479583.0, filed on October 23, 2024, entitled “Capacitive Pressure Sensor and Pressure Detection Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of pressure sensor technology, specifically to capacitive pressure sensors and pressure detection equipment. Background Technology

[0004] A capacitive pressure sensor is a type of pressure sensor that uses a capacitive sensing element to convert the measured pressure into an electrical output that is related to it. Generally, the change in air pressure is calculated by measuring the change in capacitance between a variable electrode layer and a fixed electrode layer. The variable electrode layer is typically a metal or silicon-based thin film. When the film deforms in response to pressure, the capacitance between the film and the fixed electrode layer changes, and the measuring circuit outputs an electrical signal that is related to the voltage.

[0005] Since the capacitive signal of a capacitive pressure sensor is typically dominated by the direct pressure response of a thin film, increasing the sensitivity of the thin film reduces the linear measurement range, while increasing the linear measurement range requires reducing the sensitivity of the thin film. In other words, existing capacitive pressure sensors struggle to balance sensitivity and linear measurement range, thus limiting their performance.

[0006] Summary of the Invention

[0007] In view of this, this application provides a capacitive pressure sensor and a pressure detection device to solve the problem that existing capacitive pressure sensors are unable to balance sensitivity and linear measurement range, resulting in limited performance of capacitive pressure sensors.

[0008] In a first aspect, this application provides a capacitive pressure sensor, comprising:

[0009] Fixed electrode layer;

[0010] An insulating layer is disposed at the upper end of the fixed electrode layer, and a groove is formed on the upper surface of the insulating layer;

[0011] A variable electrode layer seals the opening of the groove and forms a sealed cavity; the fixed electrode layer and the variable electrode layer form a variable capacitor.

[0012] The response of the variable electrode layer and the sealed cavity to air pressure is determined based on the unit area sensitivity of the capacitive pressure sensor. The degree of deformation of the variable electrode layer is determined based on the response of the variable electrode layer and the sealed cavity to air pressure. The change in capacitance reading of the capacitive pressure sensor is determined based on the degree of deformation of the variable electrode layer. The air pressure value of the capacitive pressure sensor is determined based on the change in capacitance reading.

[0013] The formula for calculating the sensitivity S per unit area of ​​the capacitive pressure sensor is as follows:

[0014] Where C is capacitance, P o For external air pressure, ω c Let M be the displacement of the center point of the variable electrode layer, A be the area of ​​the variable electrode layer, and M be the displacement of the center point of the variable electrode layer. C The capacitance C is the displacement ω of the center point of the variable electrode layer. c Sensitivity per unit area of ​​change, K m K is the equivalent spring constant of the variable electrode layer. P The equivalent spring constant of the sealed cavity;

[0015] The equivalent spring coefficient K of the sealed cavity P K, which is equivalent to the spring coefficient of the variable electrode layer m The ratio is greater than or equal to the preset value.

[0016] Beneficial Effects: The capacitive pressure sensor provided in this application uses a fixed electrode layer and a variable electrode layer to form a variable capacitor. When the external air pressure changes, the variable electrode layer deforms under the pressure difference between the external air pressure and the air pressure inside the sealed cavity. The response of the variable electrode layer and the sealed cavity to air pressure is determined based on the sensitivity per unit area. The degree of deformation of the variable electrode layer is calculated based on the response of the variable electrode layer and the sealed cavity to air pressure. Then, the change in capacitance reading is calculated based on the degree of deformation of the variable electrode layer. Finally, the air pressure value is obtained based on the change in capacitance reading. (K) P / K m When the value exceeds the preset value, the performance of the capacitive pressure sensor is determined by the equivalent spring coefficient K of the sealed cavity. P The nonlinearity of the capacitance due to the deformation of the variable electrode layer and the nonlinearity of the deformation of the variable electrode layer due to changes in external air pressure can cancel each other out. Therefore, this application can maintain high sensitivity while taking into account high linearity, that is, it can simultaneously improve the sensitivity and linear measurement range of the capacitive pressure sensor, thereby significantly improving the performance of the capacitive pressure sensor.

[0017] In one alternative implementation, the variable electrode layer has a regular shape, which includes one of the following: a circle, an ellipse, or a polygon.

[0018] In one optional embodiment, the variable electrode layer is a circular conductive film, and the equivalent spring coefficient K of the variable electrode layer is... m The calculation formula is as follows:

[0019] Where E is the Young's modulus of the variable electrode layer, h is the thickness of the variable electrode layer, R is the radius of the variable electrode layer, and σ o ν represents the prestress of the variable electrode layer, and ν represents the Poisson's ratio of the variable electrode layer.

[0020] In one optional embodiment, the equivalent spring coefficient K of the sealed cavity P The calculation formula is as follows:

[0021] Where g is the depth of the sealed cavity, P i The initial pressure inside the sealed cavity.

[0022] In one alternative implementation, the preset value is 5.

[0023] In one optional embodiment, the variable electrode layer is a square conductive film, and the equivalent spring coefficient K of the variable electrode layer is... m The calculation formula is as follows:

[0024] Where E is the Young's modulus of the variable electrode layer, h is the thickness of the variable electrode layer, R is the radius of the variable electrode layer, and σ o Let ν be the prestress of the variable electrode layer, ν be the Poisson's ratio of the variable electrode layer, B1 and B2 be dimensionless constants, L be the side length of the variable electrode layer, and f(ν) be a geometric function.

[0025] In one alternative implementation, the capacitor C is displaced by ω at the center point of the variable electrode layer. c Sensitivity to change M C The calculation formula is as follows:

[0026] Among them, L c ε0 is the equivalent distance between the fixed electrode layer and the variable electrode layer, and ε0 is the vacuum dielectric constant.

[0027] In one optional embodiment, the equivalent distance L between the fixed electrode layer and the variable electrode layer c The calculation formula is as follows:

[0028] Where g is the depth of the sealed cavity, t is the thickness of the insulating layer at the bottom of the sealed cavity, and ε gε is the relative permittivity of the sealed cavity. r is the relative permittivity of the insulating layer.

[0029] In one optional embodiment, the nonlinearity δ of the capacitive pressure sensor is calculated using the following formula:

[0030] Where, ΔC max C represents the maximum difference between the measured value and the linearly fitted value of the capacitance C. FS This represents the capacitance change at full scale.

[0031] Secondly, this application also provides a pressure detection device, including: the above-mentioned capacitive pressure sensor.

[0032] Beneficial effects: Because the pressure detection device includes a capacitive pressure sensor, it has the same effect as the capacitive pressure sensor, that is, it can maintain high sensitivity while taking into account high linearity. In other words, it can simultaneously improve the sensitivity and linear measurement range of the capacitive pressure sensor, thereby significantly improving the performance of the capacitive pressure sensor. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 is a schematic diagram of the structure of a first type of capacitive pressure sensor according to an embodiment of this application;

[0035] Figure 2 shows K in an embodiment of this application. P / K m Corresponding graph showing the relationship between the variable electrode layer diameter-to-thickness ratio D / h and the sealing cavity depth g;

[0036] Figure 3 is a graph showing the sensitivity variation trend of an embodiment of this application;

[0037] Figure 4 is a comparison diagram of the relationship between sensitivity and nonlinearity in an embodiment of this application;

[0038] Figure 5 is a schematic diagram of the structure of the second type of capacitive pressure sensor according to an embodiment of this application;

[0039] Figure 6 is a schematic diagram of the structure of a third type of capacitive pressure sensor according to an embodiment of this application;

[0040] Figure 7 is a schematic diagram of the structure of the fourth type of capacitive pressure sensor according to an embodiment of this application;

[0041] Figure 8 is a structural schematic diagram of the fifth type of capacitive pressure sensor according to an embodiment of this application.

[0042] Explanation of reference numerals in the attached figures:

[0043] 1. Fixed electrode layer; 2. Insulating layer; 3. Variable electrode layer; 4. Sealed cavity; 5. Lead wire. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0045] The embodiments of this application are described below with reference to Figures 1 to 8.

[0046] According to an embodiment of this application, as shown in FIG1, a capacitive pressure sensor is provided, mainly comprising a fixed electrode layer 1, an insulating layer 2, and a variable electrode layer 3. The insulating layer 2 is disposed at the upper end of the fixed electrode layer 1, and a groove is formed on the upper surface of the insulating layer 2. The variable electrode layer 3 seals the opening of the groove and forms a sealed cavity 4, and the fixed electrode layer 1 and the variable electrode layer 3 form a variable capacitor. The response of the variable electrode layer 3 and the sealed cavity 4 to air pressure is determined based on the unit area sensitivity of the capacitive pressure sensor; the degree of deformation of the variable electrode layer 3 is determined based on the response of the variable electrode layer 3 and the sealed cavity 4 to air pressure; the change in capacitance reading of the capacitive pressure sensor is determined based on the degree of deformation of the variable electrode layer 3; and the air pressure value of the capacitive pressure sensor is determined based on the change in capacitance reading.

[0047] According to the definition of sensitivity per unit area S, the formula for calculating the sensitivity per unit area S of a capacitive pressure sensor is as follows:

[0048] Where C is capacitance, P o For external air pressure, ω c Let M be the displacement of the center point of the variable electrode layer 3, A be the area of ​​the variable electrode layer 3, and M be the displacement of the center point of the variable electrode layer 3. C The capacitance C is the result of the displacement ω of the center point of the variable electrode layer 3. c Sensitivity per unit area of ​​change, K m K is the equivalent spring constant of the variable electrode layer. P This is the equivalent spring coefficient of the sealed cavity.

[0049] As can be seen from the above formula, the sensitivity S per unit area is mainly related to M. C Km and K P Related.

[0050] Equivalent spring coefficient K of the sealed cavity P K, equivalent to the spring constant of the variable electrode layer m The ratio is greater than or equal to a preset value, so that the performance of the capacitive pressure sensor is determined by the equivalent spring coefficient K of the sealed cavity. P leading.

[0051] The capacitive pressure sensor provided in this embodiment of the application uses a fixed electrode layer 1 and a variable electrode layer 3 to form a variable capacitor. When the external air pressure changes, the variable electrode layer 3 deforms under the pressure difference between the external air pressure and the air pressure inside the sealed cavity 4. The response of the variable electrode layer 3 and the sealed cavity 4 to air pressure is determined based on the sensitivity per unit area. The degree of deformation of the variable electrode layer 3 is calculated based on the response of the variable electrode layer 3 and the sealed cavity 4 to air pressure. Then, the change in capacitance reading is calculated based on the degree of deformation of the variable electrode layer 3. Finally, the air pressure value is obtained based on the change in capacitance reading. The change in capacitance with the displacement of the variable electrode layer 3 is non-linear, and the change in displacement of the variable electrode layer 3 with the external air pressure is also non-linear. In K... P / K m When the value exceeds the preset value, the performance of the capacitive pressure sensor is determined by the equivalent spring coefficient K of the sealed cavity. P The nonlinearity of the capacitance change with the displacement of the variable electrode layer 3 and the nonlinearity of the displacement of the variable electrode layer 3 with the change of external air pressure can cancel each other out. Therefore, the embodiments of this application can maintain high sensitivity while taking into account high linearity, that is, they can simultaneously improve the sensitivity and linear measurement range of the capacitive pressure sensor, thereby significantly improving the performance of the capacitive pressure sensor.

[0052] K of traditional capacitive pressure sensors P / K m <0.5, the performance of a capacitive pressure sensor is mainly determined by the equivalent spring coefficient K of the variable electrode layer. m The performance of the capacitive pressure sensor provided in this application embodiment is mainly determined by the equivalent spring coefficient K of the sealed cavity. P Decide.

[0053] It should be noted that K P / K m The preset value can be selected and set according to actual needs, as long as the performance of the capacitive pressure sensor is mainly determined by the equivalent spring coefficient K of the sealed cavity. P Make a decision.

[0054] Furthermore, the embodiments of this application do not limit the structure of the fixed electrode layer 1 and the insulating layer 2, and any existing structure can be selected as needed.

[0055] In one embodiment, as shown in Figure 1, the bottom of the insulating layer 2 is disposed on the upper surface of the fixed electrode layer 1. The fixed electrode layer 1 can be a conductive substrate, and the variable electrode layer 3 can be a conductive film. The conductive substrate and the conductive film are respectively connected to the circuit board via leads 5 to form a variable capacitor. The leads 5 can be disposed on the top surface of the conductive substrate. The conductive film is parallel to the bottom surface of the groove and has sealing properties. The actual external air pressure value can be calculated by detecting the change in the variable capacitance. The change in the variable capacitance is determined by the degree of deformation of the variable electrode layer 3, which is determined by the response of the variable electrode layer 3 and the sealed cavity 4 to air pressure. The insulating layer 2 can prevent the fixed electrode layer 1 and the variable electrode layer 3 from being directly connected and forming a short circuit.

[0056] In other embodiments, as shown in Figures 5 and 6, the leads 5 of the conductive substrate may also be disposed on its front, back, or bottom surface.

[0057] In one embodiment, as shown in FIG7, the fixed electrode layer 1 may also be disposed inside the insulating layer 2 and located at the lower end of the groove. In this case, a substrate is not used as the fixed electrode layer 1. The insulating layer 2 is divided into an upper half forming the groove and a lower half on which the fixed electrode layer 1 is mounted.

[0058] In one embodiment, as shown in FIG8, the variable electrode layer 3 can be set separately, that is, the membrane itself is not conductive, but a layer of conductive material is set on the membrane. The conductive material can be set on the upper surface, lower surface or inside of the membrane.

[0059] Of course, the structures of the fixed electrode layer 1 and the variable electrode layer 3 can be selected in other forms as needed, which will not be listed one by one in the embodiments of this application.

[0060] In one embodiment, the variable electrode layer 3 has a regular shape, which includes one of the following: a circle, an ellipse, or a polygon, wherein the polygon includes triangles, squares, etc.

[0061] Optionally, in one embodiment, the variable electrode layer 3 is a circular conductive film, and correspondingly, the sealing cavity 4 is a cylindrical chamber. Compared to other shapes, setting the variable electrode layer 3 as a disk-shaped conductive film allows for greater displacement under the same pressure, and also more evenly distributes the pressure difference on the variable electrode layer 3, which is beneficial for improving the accuracy and stability of the capacitive pressure sensor.

[0062] Specifically, the equivalent spring coefficient K of the variable electrode layer m The calculation needs to consider the linear and nonlinear segments of the deformation of the variable electrode layer 3, i.e., K. m =K m1 +K m2 , specifically,

[0063] Therefore, the equivalent spring coefficient K of the variable electrode layer m The calculation formula is as follows:

[0064] Where E is the Young's modulus of the variable electrode layer 3, h is the thickness of the variable electrode layer 3, R is the radius of the variable electrode layer 3, and σ o Let ν be the prestress of the variable electrode layer 3, and ν be the Poisson's ratio of the variable electrode layer 3. Due to the Young's modulus E and the prestress σ of the variable electrode layer 3... o And since Poisson's ratio ν is a constant, the equivalent spring coefficient K of the variable electrode layer is... m The radius R and thickness h of the variable electrode layer 3 can be adjusted. Specifically, increasing the diameter-to-thickness ratio D / h of the variable electrode layer 3 can reduce the equivalent spring coefficient K of the variable electrode layer. m .

[0065] Optionally, in one embodiment, the equivalent spring coefficient K of the sealed cavity is... P The calculation formula is as follows:

[0066] Where g is the depth of the sealed cavity 4, P i The initial pressure within the sealed cavity 4 is determined by adjusting the depth g of the sealed cavity 4 and the initial pressure P within it. i The equivalent spring coefficient K of the sealed cavity can be changed. P To reduce operating costs, the initial pressure P within the sealed cavity 4 is... i Generally, it is within a certain range. Therefore, by reducing the depth g of the sealing cavity 4, the equivalent spring coefficient K of the sealing cavity can be increased. P .

[0067] According to K m and K P According to the calculation formula, increasing the radius R of the variable electrode layer 3, decreasing the thickness h of the variable electrode layer 3, and decreasing the depth g of the sealing cavity 4 can increase K. P / K m This increases the sensitivity and linear measurement range of the capacitive pressure sensor by adjusting the equivalent spring coefficient K of the variable electrode layer. m It was decided to adjust the equivalent spring coefficient K of the sealed cavity. P Decide.

[0068] For example, as shown in Figure 2, the depth g of the sealing cavity 4 is set to 100 nm, 300 nm, and 500 nm respectively. It can be seen that the larger the diameter-to-thickness ratio D / h of the variable electrode layer 3, the smaller the depth g of the sealing cavity 4. P / K m The larger. In K P / K mWhen the value is increased to greater than 5, the performance of the capacitive pressure sensor is mainly determined by the equivalent spring coefficient K of the sealed cavity. P Decide.

[0069] In one embodiment, the variable electrode layer 3 is a square conductive film, in which case the equivalent spring coefficient K of the variable electrode layer is... m The calculation formula is as follows:

[0070] Where E is the Young's modulus of the variable electrode layer 3, h is the thickness of the variable electrode layer 3, R is the radius of the variable electrode layer 3, and σ o Let ν be the prestress of the variable electrode layer 3, ν be the Poisson's ratio of the variable electrode layer 3, B1 and B2 be dimensionless constants, L be the side length of the variable electrode layer 3, and f(ν) be a geometric function related to the Poisson's ratio. f(ν) can be taken as 0.271×ν.

[0071] It is understood that the variable electrode layer 3 can also be selected in other regular shapes as needed, and the corresponding calculation formula can be calculated according to its specific shape. In this application, the embodiments will not be listed one by one.

[0072] For ease of description, this application uses a circular conductive film as an example to illustrate the embodiments of the variable electrode layer 3.

[0073] In one embodiment, the capacitance C shifts with the center point displacement ω of the variable electrode layer 3. c Sensitivity to change M C The capacitance C is determined by the positional change between the fixed electrode layer 1 and the variable electrode layer 3. According to the formula for calculating the capacitance between parallel plates, the capacitance C changes with the displacement ω of the center point of the variable electrode layer 3. c Sensitivity to change M C The calculation formula is as follows:

[0074] Among them, L c ε0 is the equivalent distance between the fixed electrode layer 1 and the variable electrode layer 3, and ε0 is the vacuum permittivity.

[0075] Optionally, the equivalent distance L between the fixed electrode layer 1 and the variable electrode layer 3 c The calculation formula is as follows:

[0076] Where g is the depth of the sealed cavity 4, t is the thickness of the insulating layer 2 at the bottom of the sealed cavity 4, and ε g ε is the relative permittivity of the sealed cavity 4. r is the relative permittivity of insulating layer 2.

[0077] According to M C and L cAs can be seen from the calculation formula, in order to further cancel out the nonlinearity of the change of capacitance with the displacement of variable electrode layer 3 and the nonlinearity of the change of displacement of variable electrode layer 3 with the change of external air pressure, it is also necessary to select a suitable thickness t of insulating layer 2.

[0078] As shown in Figure 3, with the diameter D of the variable electrode layer 3 being 200 μm and the thickness h of the variable electrode layer 3 being 1.7 μm, the initial pressure P inside the sealed cavity 4 is... i Taking 101 kPa as an example. Within the range of 0-180 kPa, when the depth g of the sealed cavity 4 is 2000 μm, K... P / K m It is 0.14, as shown by the dashed line M in Figure 3. c / K m As shown. When the depth g of the sealed cavity 4 decreases to 50 μm, K P / K m The value is 6.6, as shown by the dotted line M in Figure 3. c / K p As shown. When the depth g of the sealed cavity 4 decreases to 50 μm and the thickness t of the insulating layer 2 is increased, the equivalent distance L between the fixed electrode layer 1 and the variable electrode layer 3 is increased. c When it is 90nm, K P / K m It remains at 6.6, but it is able to maintain a basically linear height, as shown by the dashed line M in Figure 3. c -end / K p As shown.

[0079] In one embodiment, the lower the nonlinearity of the capacitive pressure sensor, the wider its linear measurement range. The formula for calculating the nonlinearity δ of the capacitive pressure sensor is as follows:

[0080] Where, ΔC max C represents the maximum difference between the measured value and the linearly fitted value of the capacitance C. FS This represents the capacitance change at full scale.

[0081] This application embodiment improves K. P / K m And adjust L c The method of simultaneously improving sensitivity and linear measurement range is effective for variable electrode layers of various sizes. With a Poisson's ratio ν of 0.4 and a prestress σ... o The initial pressure P of the conductive film with a pressure of 150 MPa and a Young's modulus E of 100 GPa within the sealed cavity 4. i Taking 101 kPa as an example, the relationship between sensitivity and nonlinearity is shown in Figure 4.

[0082] Example 1:

[0083] The variable electrode layer 3 has a diameter D of 50 μm, a thickness h of 17 nm, and a sealing cavity 4 depth g of 300 nm, which ensures K P / K m >5, and simultaneously the equivalent distance L between the fixed electrode layer 1 and the variable electrode layer 3 is... c Set to 450nm.

[0084] Example 2:

[0085] The variable electrode layer 3 has a diameter D of 85 μm, a thickness h of 80 nm, and a sealing cavity 4 depth g of 200 nm, which ensures K P / K m >5, and simultaneously the equivalent distance L between the fixed electrode layer 1 and the variable electrode layer 3 is... c Set to 300nm.

[0086] Example 3:

[0087] The variable electrode layer 3 has a diameter D of 80 μm, a thickness h of 40 nm, and a sealing cavity 4 depth g of 350 nm, which ensures K P / K m >5, and simultaneously the equivalent distance L between the fixed electrode layer 1 and the variable electrode layer 3 is... c Set to 500nm.

[0088] To realize the basic functions of a capacitive pressure sensor, the capacitive pressure sensor in this embodiment may also include other necessary modules or components, such as a housing, wires, etc. It should be noted that the other necessary modules or components included in the capacitive pressure sensor can be any suitable existing structure. To clearly and concisely illustrate the technical solution provided in this embodiment, the above-mentioned parts will not be repeated here, and the accompanying drawings have also been simplified accordingly. However, it should be understood that the scope of the embodiments of this application is not limited thereto.

[0089] According to an embodiment of this application, another aspect provides a pressure detection device, including a capacitive pressure sensor.

[0090] Because the pressure detection device includes a capacitive pressure sensor, it has the same effect as the capacitive pressure sensor, namely, it can maintain high sensitivity while taking into account high linearity. In other words, it can simultaneously improve the sensitivity and linear measurement range of the capacitive pressure sensor, thereby significantly improving the performance of the capacitive pressure sensor.

[0091] Specifically, after a pressure detection device detects a change in air pressure using a capacitive pressure sensor, it can also determine the device's altitude based on the air pressure value. Therefore, pressure detection devices include, but are not limited to, mobile devices, indoor navigation devices, altitude positioning devices, and industrial air pressure monitoring devices.

[0092] Taking mobile devices as an example, in outdoor sports scenarios, the capacitive pressure sensor inside the wristband can detect the real-time air pressure of the user's environment.

[0093] Taking industrial air pressure monitoring equipment as an example, when industrial production requires air pressure within a specified concentration range, a capacitive pressure sensor can be used to detect the gas concentration applied by the industrial equipment.

[0094] Although embodiments of this application have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of this application, and all such modifications and variations fall within the scope defined by the appended claims.

Claims

A capacitive pressure sensor, characterized in that, include: Fixed electrode layer (1); An insulating layer (2) is disposed at the upper end of the fixed electrode layer (1), and a groove is formed on the upper surface of the insulating layer (2); A variable electrode layer (3) seals the opening of the groove and forms a sealed cavity (4), and the fixed electrode layer (1) and the variable electrode layer (3) form a variable capacitor; The response of the variable electrode layer (3) and the sealed cavity (4) to air pressure is determined based on the unit area sensitivity of the capacitive pressure sensor. The degree of deformation of the variable electrode layer (3) is determined based on the response of the variable electrode layer (3) and the sealed cavity (4) to air pressure. The change in capacitance reading of the capacitive pressure sensor is determined based on the degree of deformation of the variable electrode layer (3). The air pressure value of the capacitive pressure sensor is determined based on the change in capacitance reading. The formula for calculating the sensitivity S per unit area of ​​the capacitive pressure sensor is as follows: Where C is capacitance, P o For external air pressure, ω c Let M be the displacement of the center point of the variable electrode layer (3), A be the area of ​​the variable electrode layer (3), and M be the displacement of the center point of the variable electrode layer (3). C The capacitance C is the resultant of the displacement ω of the center point of the variable electrode layer (3). c Sensitivity per unit area of ​​change, K m K is the equivalent spring constant of the variable electrode layer. P The equivalent spring constant of the sealed cavity; The equivalent spring coefficient K of the sealed cavity P K, which is equivalent to the spring coefficient of the variable electrode layer m The ratio is greater than or equal to the preset value. The capacitive pressure sensor according to claim 1 is characterized in that, The variable electrode layer (3) has a regular shape, which includes one of the following: circle, ellipse, and polygon. The capacitive pressure sensor according to claim 2 is characterized in that, The variable electrode layer (3) is a circular conductive film, and the equivalent spring coefficient K of the variable electrode layer is... m The calculation formula is as follows: Where E is the Young's modulus of the variable electrode layer (3), h is the thickness of the variable electrode layer (3), R is the radius of the variable electrode layer (3), and σ o Prestressing of the variable electrode layer (3) Force, where ν is the Poisson's ratio of the variable electrode layer (3). The capacitive pressure sensor according to claim 3 is characterized in that, The equivalent spring coefficient K of the sealed cavity P The calculation formula is as follows: Where g is the depth of the sealed cavity (4), P i The initial pressure inside the sealed cavity (4) is given. The capacitive pressure sensor according to claim 4 is characterized in that, The preset value is 5. The capacitive pressure sensor according to claim 2 is characterized in that, The variable electrode layer (3) is a square conductive film, and the equivalent spring coefficient K of the variable electrode layer is... m The calculation formula is as follows: Where E is the Young's modulus of the variable electrode layer (3), h is the thickness of the variable electrode layer (3), R is the radius of the variable electrode layer (3), and σ o ν is the prestress of the variable electrode layer (3), B1 and B2 are dimensionless constants, L is the side length of the variable electrode layer (3), and f(ν) is a geometric function. The capacitive pressure sensor according to any one of claims 1 to 6 is characterized in that, The capacitance C is affected by the displacement ω of the center point of the variable electrode layer (3). c Sensitivity to change M C The calculation formula is as follows: Among them, L c ε0 is the equivalent distance between the fixed electrode layer (1) and the variable electrode layer (3), and ε0 is the vacuum dielectric constant. The capacitive pressure sensor according to claim 7 is characterized in that, The equivalent distance L between the fixed electrode layer (1) and the variable electrode layer (3) c The calculation formula is as follows: Where g is the depth of the sealed cavity (4), and t is the insulating layer (2) at the bottom of the sealed cavity (4). The thickness, ε g ε is the relative permittivity of the sealed cavity (4). r is the relative permittivity of the insulating layer (2). The capacitive pressure sensor according to any one of claims 1 to 6 is characterized in that, The formula for calculating the nonlinearity δ of the capacitive pressure sensor is as follows: Where, ΔC max C represents the maximum difference between the measured value and the linearly fitted value of the capacitance C. FS This represents the capacitance change at full scale. A pressure testing device, characterized in that, include: The capacitive pressure sensor according to any one of claims 1 to 9.

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