Capacitive pressure sensor and pressure detection equipment

Abstract

The present invention relates to the technical field of pressure sensors, and discloses a capacitive pressure sensor and a pressure detection device, wherein the capacitive pressure sensor mainly includes: a fixed electrode layer, an insulating layer and a variable electrode layer. The insulating layer is arranged at the upper end of the fixed electrode layer, and a groove is opened on the upper surface of the insulating layer; the variable electrode layer seals the notch of the groove and forms a sealed cavity, and the fixed electrode layer and the variable electrode layer form a variable capacitor; the response of the variable electrode layer and the sealed cavity to the air pressure is determined according to the unit area sensitivity, the deformation degree of the variable electrode layer is determined according to the response of the variable electrode layer and the sealed cavity to the air pressure, the capacitance reading change is determined according to the deformation degree of the variable electrode layer, and the air pressure value is determined according to the capacitance reading change. The capacitive pressure sensor provided by the present invention has a performance dominated by the equivalent spring coefficient of the sealed cavity, which can simultaneously improve the sensitivity and linear measurement range of the capacitive pressure sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure sensors, and in particular to a capacitive pressure sensor and a pressure detection device. Background Art

[0002] A capacitive pressure sensor is a pressure sensor that uses a capacitive sensitive element to convert the measured pressure into an electrical output that is in a certain relationship with it. Generally, the change in air pressure is calculated by measuring the change in capacitance between the variable electrode layer and the fixed electrode layer. The variable electrode layer is usually a metal or silicon-based film. When the film deforms due to pressure, the capacitance formed between the film and the fixed electrode layer changes, and an electrical signal in a certain relationship with the voltage can be output through the measurement circuit.

[0003] Since the capacitance signal of a capacitive pressure sensor is usually dominated by the film's direct response to pressure, if the film's sensitivity is increased, the linear measurement range will be reduced, and if the linear measurement range is increased, the film's sensitivity needs to be reduced. In other words, it is difficult for existing capacitive pressure sensors to balance sensitivity and linear measurement range, resulting in limited performance of capacitive pressure sensors. Summary of the invention

[0004] In view of this, the present invention provides a capacitive pressure sensor and a pressure detection device to solve the problem that the existing capacitive pressure sensor is difficult to balance sensitivity and linear measurement range, resulting in limited performance of the capacitive pressure sensor.

[0005] In a first aspect, the present invention provides a capacitive pressure sensor, comprising:

[0006] Fixed electrode layer;

[0007] An insulating layer, disposed on the upper end of the fixed electrode layer, wherein a groove is formed on the upper surface of the insulating layer;

[0008] A variable electrode layer, sealing the notch of the groove and forming a sealed cavity, wherein the fixed electrode layer and the variable electrode layer form a variable capacitor;

[0009] Determine the response of the variable electrode layer and the sealed cavity to the air pressure according to the unit area sensitivity of the capacitive pressure sensor, determine the deformation degree of the variable electrode layer according to the response of the variable electrode layer and the sealed cavity to the air pressure, determine the change of the capacitance reading of the capacitive pressure sensor according to the deformation degree of the variable electrode layer, and determine the air pressure value of the capacitive pressure sensor according to the change of the capacitance reading;

[0010] The calculation formula of the unit area sensitivity S of the capacitive pressure sensor is as follows:

[0011]

[0012] Where C is the capacitance, P o is the external air pressure, ω c is the displacement of the center point of the variable electrode layer, A is the area of ​​the variable electrode layer, M C is the capacitance C as the center point of the variable electrode layer shifts ω c Sensitivity per unit area of ​​change, K m is the equivalent spring coefficient of the variable electrode layer, K P is the equivalent spring coefficient of the sealing chamber;

[0013] The sealing chamber equivalent spring coefficient K P The variable electrode layer has an equivalent spring coefficient K m The ratio is greater than or equal to the preset value.

[0014] Beneficial effect: The capacitive pressure sensor provided by the present invention forms a variable capacitor with a fixed electrode layer and a variable electrode layer. When the external air pressure changes, the variable electrode layer is deformed by the difference between the external air pressure and the air pressure in the sealed cavity. The response of the variable electrode layer and the sealed cavity to the air pressure is determined according to the unit area sensitivity, the deformation degree of the variable electrode layer is calculated according to the response of the variable electrode layer and the sealed cavity to the air pressure, and then the capacitance reading change is calculated according to the deformation degree of the variable electrode layer. Finally, the pressure value is obtained according to the capacitance reading change. P / K m When the value is greater than the preset value, the performance of the capacitive pressure sensor is determined by the equivalent spring coefficient K of the sealing chamber. P Mainly, the nonlinearity of the capacitance with the deformation of the variable electrode layer and the nonlinearity of the deformation of the variable electrode layer with the change of the external air pressure can offset each other. Therefore, the present invention 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.

[0015] In an optional embodiment, the variable electrode layer is a regular shape, and the regular shape includes one of a circle, an ellipse, and a polygon.

[0016] In an optional embodiment, the variable electrode layer is a circular conductive diaphragm, and the equivalent spring coefficient K of the variable electrode layer is m The calculation formula is as follows:

[0017]

[0018] Wherein, 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, σ o is the prestress of the variable electrode layer, and ν is the Poisson's ratio of the variable electrode layer.

[0019] In an optional embodiment, the sealing chamber equivalent spring coefficient K P The calculation formula is as follows:

[0020]

[0021] Wherein, g is the depth of the sealed cavity, P i is the initial pressure in the sealed cavity.

[0022] In an optional implementation, the preset value is 5.

[0023] In an optional implementation, the variable electrode layer is a square conductive diaphragm, and the equivalent spring coefficient K of the variable electrode layer is m The calculation formula is as follows:

[0024]

[0025] Wherein, 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, σ o is the prestress of the variable electrode layer, ν is the Poisson's ratio of the variable electrode layer, B1 and B2 are dimensionless constants, L is the side length of the variable electrode layer, and f(ν) is a geometric function.

[0026] In an optional embodiment, the capacitance C changes with the displacement ω of the center point of the variable electrode layer. c Sensitivity to change M C The calculation formula is as follows:

[0027]

[0028] Among them, L c is the equivalent distance between the fixed electrode layer and the variable electrode layer, and ε0 is the dielectric constant of vacuum.

[0029] In an optional implementation, the equivalent distance L between the fixed electrode layer and the variable electrode layer is c The calculation formula is as follows:

[0030]

[0031] Wherein, g is the depth of the sealed cavity, t is the thickness of the insulating layer at the bottom of the sealed cavity, ε g is the relative dielectric constant of the sealed cavity, ε r is the relative dielectric constant of the insulating layer.

[0032] In an optional implementation, the nonlinearity of the capacitive pressure sensor is The calculation formula is as follows:

[0033]

[0034] Where, ΔC max is the maximum value of the difference between the measured value of capacitance C and the linear fitting value, C FS is the full-scale capacitance change.

[0035] In a second aspect, the present invention further provides a pressure detection device, comprising: the above-mentioned capacitive pressure sensor.

[0036] Beneficial effect: 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, 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 is a schematic structural diagram of a first capacitive pressure sensor according to an embodiment of the present invention;

[0039] Figure 2 K in the embodiment of the present invention P / K m Corresponding diagram of the relationship between the variable electrode layer diameter-thickness ratio D / h and the sealed cavity depth g;

[0040] Figure 3 This is a sensitivity change trend diagram of an embodiment of the present invention;

[0041] Figure 4 A comparison diagram of the relationship between sensitivity and nonlinearity of an embodiment of the present invention;

[0042] Figure 5 is a schematic structural diagram of a second capacitive pressure sensor according to an embodiment of the present invention;

[0043] Figure 6 is a schematic structural diagram of a third capacitive pressure sensor according to an embodiment of the present invention;

[0044] Figure 7is a schematic structural diagram of a fourth capacitive pressure sensor according to an embodiment of the present invention;

[0045] Figure 8 Schematic diagram of the structure of a fifth capacitive pressure sensor according to an embodiment of the present invention.

[0046] Description of reference numerals:

[0047] 1. Fixed electrode layer; 2. Insulation layer; 3. Variable electrode layer; 4. Sealed cavity; 5. Lead wire. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0049] Combine the following Figures 1 to 8 , describing an embodiment of the present invention.

[0050] According to an embodiment of the present invention, on the one hand, Figure 1 As shown, a capacitive pressure sensor is provided, which mainly includes a fixed electrode layer 1, an insulating layer 2 and a variable electrode layer 3. The insulating layer 2 is arranged at the upper end of the fixed electrode layer 1, and a groove is opened on the upper surface of the insulating layer 2. The variable electrode layer 3 seals the notch 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 the air pressure is determined according to the unit area sensitivity of the capacitive pressure sensor, the deformation degree of the variable electrode layer 3 is determined according to the response of the variable electrode layer 3 and the sealed cavity 4 to the air pressure, the capacitance reading change of the capacitive pressure sensor is determined according to the deformation degree of the variable electrode layer 3, and the air pressure value of the capacitive pressure sensor is determined according to the capacitance reading change.

[0051] According to the definition of unit area sensitivity S, the calculation formula of unit area sensitivity S of capacitive pressure sensor is as follows:

[0052]

[0053] Where C is the capacitance, P o is the external air pressure, ω c is the displacement of the center point of the variable electrode layer 3, A is the area of ​​the variable electrode layer 3, M C The capacitance C is shifted by the center point of the variable electrode layer 3 ω c Sensitivity per unit area of ​​change, K mis the equivalent spring coefficient of the variable electrode layer, K P is the equivalent spring coefficient of the sealing chamber.

[0054] From the above formula, we can see that the unit area sensitivity S is mainly related to M C , K m and K P Related.

[0055] Equivalent spring coefficient of sealing chamber K P K of the equivalent spring constant of the variable electrode layer m The ratio is greater than or equal to the preset value, so that the performance of the capacitive pressure sensor is determined by the equivalent spring coefficient K of the sealing chamber. P leading.

[0056] In the capacitive pressure sensor provided by the embodiment of the present invention, the fixed electrode layer 1 and the variable electrode layer 3 form a variable capacitor. After the external air pressure changes, the variable electrode layer 3 is deformed by the difference between the external air pressure and the air pressure in the sealed cavity 4. The response of the variable electrode layer 3 and the sealed cavity 4 to the air pressure is determined based on the unit area sensitivity, and 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 the air pressure. The change in capacitance reading is then calculated based on the degree of deformation of the variable electrode layer 3, and finally the 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 nonlinear, and the displacement of the variable electrode layer 3 with the change in external air pressure is also nonlinear. In K P / K m When the value is greater than the preset value, the performance of the capacitive pressure sensor is determined by the equivalent spring coefficient K of the sealing chamber. P Mainly, the nonlinearity of the capacitance changing with the displacement of the variable electrode layer 3 and the nonlinearity of the displacement of the variable electrode layer 3 changing with the external air pressure can offset each other. Therefore, the embodiment of the present invention 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.

[0057] The K of conventional capacitive pressure sensors P / K m <0.5, the performance of the capacitive pressure sensor is mainly determined by the variable electrode layer equivalent spring coefficient K m The performance of the capacitive pressure sensor provided by the embodiment of the present invention is mainly determined by the equivalent spring coefficient K of the sealed cavity. P Decide.

[0058] 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 sealing cavity. P Just decide.

[0059] In addition, the embodiment of the present invention does not limit the structures of the fixed electrode layer 1 and the insulating layer 2, and any existing structure can be selected as needed.

[0060] In one embodiment, Figure 1 As shown, the bottom of the insulating layer 2 is arranged 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 through the lead 5 to form a variable capacitor. The lead 5 can be arranged on the top surface of the conductive substrate. The conductive film is parallel to the bottom surface of the groove of the groove and has sealing properties. The actual external air pressure value can be calculated by detecting the change of the variable capacitance. The change of the variable capacitance is determined by the deformation degree of the variable electrode layer 3, and the deformation degree of the variable electrode layer 3 is determined by the response of the variable electrode layer 3 and the sealed cavity 4 to the air pressure. The provision of the insulating layer 2 can avoid the fixed electrode layer 1 and the variable electrode layer 3 being directly connected to form a short circuit.

[0061] In some other embodiments, such as Figure 5 and Figure 6 As shown, the leads 5 of the conductive substrate may also be arranged on the front side, back side or bottom side thereof.

[0062] In one embodiment, Figure 7 As shown, the fixed electrode layer 1 can also be arranged inside the insulating layer 2 and at the lower end of the groove. In this case, the 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 where the fixed electrode layer 1 is installed.

[0063] In one embodiment, Figure 8 As shown, the variable electrode layer 3 can be provided separately, that is, the membrane itself is not conductive, and a layer of conductive material is provided on the membrane. The conductive material can be provided on the upper surface, the lower surface or the inside of the membrane.

[0064] Of course, the structures of the fixed electrode layer 1 and the variable electrode layer 3 may also be in other forms as required, and the embodiments of the present invention will not list them one by one.

[0065] In one embodiment, the variable electrode layer 3 is in a regular shape, and the regular shape includes one of a circle, an ellipse, and a polygon, wherein the polygon includes a triangle, a square, and the like.

[0066] Furthermore, in one embodiment, the variable electrode layer 3 is a circular conductive diaphragm, and correspondingly, the sealed cavity 4 is a cylindrical cavity. Compared with other shapes, the variable electrode layer 3 is set as a disc-shaped conductive diaphragm, which has a larger displacement under the same pressure, and can evenly distribute the pressure of the air pressure difference on the variable electrode layer 3, which is conducive to improving the accuracy and stability of the capacitive pressure sensor.

[0067] Specifically, the variable electrode layer equivalent spring coefficient K m The calculation of K needs to consider the linear and nonlinear segments of the deformation of the variable electrode layer 3, that is, m = K m1 + K m2 , specifically,

[0068]

[0069]

[0070] Therefore, the variable electrode layer equivalent spring coefficient K m The calculation formula is as follows:

[0071]

[0072] Wherein, 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, σ o is the prestress of the variable electrode layer 3, and ν is the Poisson's ratio of the variable electrode layer 3. Due to the Young's modulus E of the variable electrode layer 3 and the prestress σ o And Poisson's ratio ν is a constant, so the variable electrode layer equivalent spring coefficient K m The adjustment can be made by adjusting the radius R of the variable electrode layer 3 and the thickness h of the variable electrode layer 3. 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 .

[0073] Furthermore, in one embodiment, the sealing chamber equivalent spring coefficient K P The calculation formula is as follows:

[0074]

[0075] Where, g is the depth of the sealed cavity 4, P i is the initial pressure in the sealed cavity 4. By adjusting the depth g of the sealed cavity 4 and the initial pressure P in the sealed cavity 4 i , the equivalent spring coefficient K of the sealing chamber can be changed P In order to reduce the use cost, the initial pressure P in the sealed cavity 4 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 .

[0076] According to K m and K P From the calculation formula, it can be known that increasing the radius R of the variable electrode layer 3, reducing the thickness h of the variable electrode layer 3, and reducing the depth g of the sealed cavity 4 can increase K P / Km , thus the sensitivity and linear measurement range of the capacitive pressure sensor are controlled by the variable electrode layer equivalent spring coefficient K m Decide to adjust to the equivalent spring coefficient K of the sealing chamber P Decide.

[0077] For example, Figure 2 As shown in FIG. 1 , the depth g of the sealed cavity 4 is set to 100 nm, 300 nm and 500 nm respectively. It can be seen that the larger the diameter-thickness ratio D / h of the variable electrode layer 3 is, the smaller the depth g of the sealed cavity 4 is, and K P / K m The larger the K P / K m When 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 sealing cavity. P Decide.

[0078] In one embodiment, the variable electrode layer 3 is a square conductive film. In this case, the variable electrode layer equivalent spring coefficient K m The calculation formula is as follows:

[0079]

[0080] Wherein, 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, σ o is the prestress of the variable electrode layer 3, ν is the Poisson's ratio of the variable electrode layer 3, B1 and B2 are dimensionless constants, L is the side length of the variable electrode layer 3, f(ν) is a geometric function related to the Poisson's ratio, and f(ν) can be taken as 0.271×ν.

[0081] It is understandable that the variable electrode layer 3 may also select other regular shapes as required, and the corresponding calculation formula may be calculated based on its specific shape, which will not be listed one by one in the embodiment of the present invention.

[0082] For the convenience of description, the embodiment of the present invention is described by taking the variable electrode layer 3 as a circular conductive film as an example.

[0083] In one embodiment, the capacitance C changes with the displacement ω of the center point of the variable electrode layer 3. c Sensitivity to change M C It is determined by the position change between the fixed electrode layer 1 and the variable electrode layer 3. According to the calculation formula of the capacitance between parallel plates, it can be known that 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:

[0084]

[0085] Among them, L c is the equivalent distance between the fixed electrode layer 1 and the variable electrode layer 3, and ε0 is the dielectric constant of vacuum.

[0086] Furthermore, the equivalent distance L between the fixed electrode layer 1 and the variable electrode layer 3 is c The calculation formula is as follows:

[0087]

[0088] Wherein, 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, ε g is the relative dielectric constant of the sealed cavity 4, ε r is the relative dielectric constant of the insulating layer 2.

[0089] According to M C and L c It can be seen from the calculation formula that in order to further offset the nonlinearity of the capacitance changing with the displacement of the variable electrode layer 3 and the nonlinearity of the displacement of the variable electrode layer 3 changing with the external air pressure, it is also necessary to select a suitable thickness t of the insulating layer 2.

[0090] like Figure 3 As shown, the diameter D of the variable electrode layer 3 is 200 um, the thickness h of the variable electrode layer 3 is 1.7 um, and the initial pressure P in the sealed cavity 4 is i For example, when the depth g of the sealed cavity 4 is 2000um, K P / K m is 0.14, such as Figure 3 The dotted line M c / K m As shown. When the depth g of the sealed cavity 4 decreases to 50 um, K P / K m is 6.6, such as Figure 3 The dotted line M c / K p When the depth g of the sealed cavity 4 is reduced to 50 um 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 c When the K P / K m Still 6.6, but can basically maintain the linear height, such as Figure 3 The dotted line M c -end / K p shown.

[0091] In one embodiment, the lower the nonlinearity of the capacitive pressure sensor, the wider the linear measurement range. The calculation formula of the nonlinearity δ of the capacitive pressure sensor is as follows:

[0092]

[0093] Where, ΔC max is the maximum value of the difference between the measured value of capacitance C and the linear fitting value, C FS is the full-scale capacitance change.

[0094] The embodiment of the present invention improves K P / K m And adjust L c The method of improving sensitivity and linear measurement range simultaneously is effective for variable electrode layers 3 of various sizes. o The conductive film has a Young's modulus E of 150 Mpa and a Young's modulus E of 100 Gpa. The initial pressure P in the sealed cavity 4 is i Take 101 kPa as an example. The corresponding relationship between sensitivity and nonlinearity is as follows: Figure 4 shown.

[0095] Example 1:

[0096] The diameter D of the variable electrode layer 3 is 50 um, the thickness h of the variable electrode layer 3 is 17 nm, and the depth g of the sealed cavity 4 is 300 nm, which can ensure that K P / K m >5, and at the same time, the equivalent distance L between the fixed electrode layer 1 and the variable electrode layer 3 c Set to 450 nm.

[0097] Example 2:

[0098] The diameter D of the variable electrode layer 3 is 85 um, the thickness h of the variable electrode layer 3 is 80 nm, and the depth g of the sealed cavity 4 is 200 nm, which can ensure that K P / K m >5, and at the same time, the equivalent distance L between the fixed electrode layer 1 and the variable electrode layer 3 c Set to 300 nm.

[0099] Example 3:

[0100] The diameter D of the variable electrode layer 3 is 80 um, the thickness h of the variable electrode layer 3 is 40 nm, and the depth g of the sealed cavity 4 is 350 nm, which can ensure that K P / K m >5, and at the same time, the equivalent distance L between the fixed electrode layer 1 and the variable electrode layer 3 cSet to 500 nm.

[0101] In order to realize the basic functions of the capacitive pressure sensor, the capacitive pressure sensor in this embodiment may also include other necessary modules or components, such as a housing, a wire, etc. It should be noted that the other necessary modules or components included in the capacitive pressure sensor may be any suitable existing structure. In order to clearly and briefly explain the technical solution provided by this embodiment, the above-mentioned part will not be described in detail here, and the drawings in the specification are also simplified accordingly. However, it should be understood that the scope of the embodiments of the present invention is not limited by this.

[0102] According to an embodiment of the present invention, on the other hand, a pressure detection device is provided, including: a capacitive pressure sensor.

[0103] 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, 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.

[0104] Specifically, after the pressure detection device detects the air pressure change through the capacitive pressure sensor, the height of the pressure detection device can also be determined according to the air pressure value. Therefore, the pressure detection device includes but is not limited to mobile devices, indoor navigation equipment, height positioning equipment, industrial air pressure monitoring equipment, etc.

[0105] Taking a mobile device such as a wristband as an example, in an outdoor sports scenario, the capacitive pressure sensor in the wristband can detect the real-time air pressure in the user's environment.

[0106] Taking industrial gas pressure monitoring equipment as an example, when industrial production requires the use of gas pressure within a specified concentration range, a capacitive pressure sensor can be used to detect the gas concentration applied by the industrial equipment.

[0107] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A capacitive pressure sensor, characterized in that: include: A fixed electrode layer (1); An insulating layer (2) is arranged on the upper end of the fixed electrode layer (1), and a groove is provided on the upper surface of the insulating layer (2); A variable electrode layer (3) seals the notch 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; Determining the response of the variable electrode layer (3) and the sealed cavity (4) to air pressure according to the unit area sensitivity of the capacitive pressure sensor, determining the degree of deformation of the variable electrode layer (3) according to the response of the variable electrode layer (3) and the sealed cavity (4) to air pressure, determining the change in capacitance reading of the capacitive pressure sensor according to the degree of deformation of the variable electrode layer (3), and determining the air pressure value of the capacitive pressure sensor according to the change in capacitance reading; The calculation formula of the unit area sensitivity S of the capacitive pressure sensor is as follows: Where C is the capacitance, P o is the external air pressure, ω c is the displacement of the center point of the variable electrode layer (3), A is the area of ​​the variable electrode layer (3), M C is the capacitance C as the center point of the variable electrode layer (3) is displaced ω c Sensitivity per unit area of ​​change, K m is the equivalent spring coefficient of the variable electrode layer, K P is the equivalent spring coefficient of the sealing chamber; The sealing chamber equivalent spring coefficient K P The variable electrode layer has an equivalent spring coefficient K m The ratio is greater than or equal to the preset value.

2. The capacitive pressure sensor according to claim 1, characterized in that: The variable electrode layer (3) is in a regular shape, and the regular shape includes one of a circle, an ellipse, and a polygon.

3. The capacitive pressure sensor according to claim 2, characterized in that: The variable electrode layer (3) is a circular conductive diaphragm, and the equivalent spring coefficient K of the variable electrode layer is m The calculation formula is as follows: Wherein, 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), σ o is the prestress of the variable electrode layer (3), and ν is the Poisson's ratio of the variable electrode layer (3).

4. The capacitive pressure sensor according to claim 3, characterized in that: The sealing chamber equivalent spring coefficient K P The calculation formula is as follows: Wherein, g is the depth of the sealed cavity (4), P i is the initial pressure in the sealed chamber (4).

5. The capacitive pressure sensor according to claim 4, characterized in that: The preset value is 5.

6. The capacitive pressure sensor according to claim 2, characterized in that: The variable electrode layer (3) is a square conductive diaphragm, and the equivalent spring coefficient K of the variable electrode layer is m The calculation formula is as follows: Wherein, 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), σ o is the prestress of the variable electrode layer (3), ν is the Poisson's ratio 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.

7. The capacitive pressure sensor according to any one of claims 1 to 6, characterized in that: 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: Among them, L c is the equivalent distance between the fixed electrode layer (1) and the variable electrode layer (3), and ε0 is the vacuum dielectric constant.

8. The capacitive pressure sensor according to claim 7, characterized in that: The equivalent distance L between the fixed electrode layer (1) and the variable electrode layer (3) is c The calculation formula is as follows: Wherein, 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), ε g is the relative dielectric constant of the sealed cavity (4), ε r is the relative dielectric constant of the insulating layer (2).

9. The capacitive pressure sensor according to any one of claims 1 to 6, characterized in that: The calculation formula of the nonlinearity δ of the capacitive pressure sensor is as follows: Where, ΔC max is the maximum value of the difference between the measured value of capacitance C and the linear fitting value, C FS is the full-scale capacitance change.

10. A pressure detection device, characterized in that: include: A capacitive pressure sensor as claimed in any one of claims 1 to 9.

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