WO2023037779A1 - Pressure sensor - Google Patents

Abstract

[Problem] To provide a pressure sensor capable of accurately performing temperature detection or temperature correction. [Solution] A pressure sensor 10 comprises: a membrane 22 which deforms in accordance with pressure; a plurality of sensor resistors R1 to R4 which are formed on the membrane 22 and which constitute a detecting circuit 30; a correction resistor Rc which is formed on the membrane 22, for detecting a temperature; and an external resistor Re which is formed on an external board 18 different from the membrane 22, and which can be electrically connected to one end of the correction resistor Rc.

Description

pressure sensor

The present invention relates to a pressure sensor that detects strain due to deformation of a membrane from changes in resistance of a resistor.

In recent years, various technologies have been proposed for pressure sensors that utilize the piezoresistive effect (piezoresistive effect). For example, Patent Document 1 describes a pressure sensor having a membrane (diaphragm), a plurality of resistors formed on the membrane, and a temperature measuring element formed on the membrane.

A plurality of resistors formed on the membrane form a detection circuit (strain gauge) consisting of a bridge circuit. change the value. By detecting the output signal of the detection circuit at this time, it is possible to measure the change in the resistance values of the plurality of resistors, that is, the pressure applied to the membrane.

The temperature measuring element formed on the membrane consists of a resistance element such as a thermistor, and changes the resistance value according to the temperature change of the pressure fluid. Therefore, by detecting the output signal of the temperature measuring element, the temperature of the pressure fluid can be measured. Based on this temperature information, the error contained in the output signal of the detection circuit (temperature error due to dependency) can be corrected.

By the way, in order to reduce the size of the pressure sensor or improve the accuracy of temperature measurement, it is desirable to form a temperature measuring element in the area where a plurality of resistors are arranged, that is, in the strain-generating area of the membrane. However, in this case, if the membrane receives pressure from the pressurized fluid and generates strain, the resistance change of the temperature measuring element due to the effect of the strain cannot be ignored, and the output signal of the temperature measuring element is There is a risk that the corresponding error will exceed the allowable amount and be superimposed. Therefore, the accuracy of the temperature information obtained from the output signal of the temperature measuring element cannot be ensured, and it is difficult to perform accurate temperature correction on the output signal of the detection circuit.

JP-A-11-094667

The present invention has been made in view of such problems, and its object is to provide a pressure sensor capable of accurately performing temperature detection or temperature correction.

In order to achieve the above object, the pressure sensor according to the present invention comprises:
a membrane that deforms in response to pressure;
a plurality of sensor resistors formed on the membrane and constituting a detection circuit;
a correction resistor formed on the membrane for detecting temperature;
an external resistor formed on an external substrate different from the membrane and electrically connectable to one end of the correction resistor.

For example, in a state where the correction resistor and the external resistor are not electrically connected, by detecting the output signal of the correction resistor (hereinafter, temporary output signal), the temperature of the pressure fluid (hereinafter, temporary temperature) can be measured. However, the temporary output signal may include not only the resistance change of the correction resistor caused by the temperature change of the pressure fluid, but also the resistance change of the correction resistor caused by the distortion of the membrane. be.

Therefore, by detecting the output signal of the correction resistor in a state in which the correction resistor and the external resistor are electrically connected, the change in resistance of the correction resistor caused by the distortion of the membrane can be calculated. can be specified. That is, if the temperature conditions are the same between the position where the correction resistor is arranged and the position where the external resistor is arranged, the resistance change occurs in the correction resistor according to the temperature change of the pressurized fluid. , the resistance change also occurs in the external resistor at the same rate of change. Therefore, by canceling out the resistance change of each resistor according to the temperature change, the output signal of the correction resistor (for example, the correction resistor interposed between the power supply line and the ground and the external Theoretically, the value of the voltage divided between the resistors) is equal to the resistance change of the correction resistor due to the strain of the membrane. Therefore, the true temperature of the pressurized fluid can be obtained by removing the change in the resistance of the correction resistor due to the distortion of the membrane from the detected value of the provisional output signal.

Thus, in the pressure sensor according to the present invention, the temperature of the pressure fluid can be detected with high accuracy, and the error contained in the output signal of the detection circuit (resistance change of each sensor resistor) can be detected based on the temperature information. error due to the temperature dependence of ) can be accurately corrected. Further, as described above, since the change in resistance of the correction resistor caused by the distortion of the membrane can be removed from the detected value of the temporary output signal, the correction resistor can be formed in the distortion generation region of the membrane. There is no problem, and it is possible to favorably reduce the size of the pressure sensor or improve the accuracy of temperature measurement.

The external substrate comprises a plurality of external substrates, the external resistor comprises a plurality of external resistors, and each of the plurality of external resistors is formed on each of the plurality of external substrates. The correction resistor and the plurality of external resistors may form a bridge circuit. With such a configuration, it is possible to obtain the output signal of the correction resistor as a differential output of the bridge circuit. The resistance change of the resistor can be read finely. In addition, by forming each external resistor on each external substrate, it is possible to freely adjust the arrangement of each external resistor by appropriately adjusting the installation position of each external substrate. The degree of freedom of arrangement can be increased.

The external resistor comprises a plurality of external resistors, the external substrate is formed with the plurality of external resistors, and the correction resistor and the plurality of external resistors form a bridge circuit. You may have Even in such a configuration, as described above, the output signal of the correction resistor can be obtained as a differential output of the bridge circuit. It is possible to finely read the resistance change of the correction resistor due to strain. Also, since the external resistors are formed on the same substrate, the temperature conditions at the positions where the external resistors are arranged are the same. Therefore, each external resistor undergoes a similar temperature change, and it is possible to prevent an error caused by a difference in temperature change from being included in the output signal of the correction resistor.

Preferably, the external substrate and the membrane are made of materials having similar thermal properties. With such a configuration, it is possible to make the temperature conditions the same between the position where the correction resistor is arranged and the position where the external resistor is arranged. Therefore, the correction resistor and the external resistor undergo similar temperature changes, preventing the output signal of the correction resistor from including an error caused by the difference in temperature change between the resistors. It is possible to detect the resistance change of the correction resistor due to the distortion of the membrane with high accuracy.

Preferably, it has a releasing portion for releasing the electrical connection between the correction resistor and the external resistor. When measuring the resistance change of the compensating resistor due to the temperature change of the pressurized fluid (when measuring the virtual temperature), disconnect the electrical connection between the compensating resistor and the external resistor By detecting the output signal (provisional output signal) of the correction resistor, interference with the circuit including the external resistor is avoided, and the provisional output signal is prevented from including an error due to the influence of the external resistor. be able to. That is, as described above, the temporary output signal includes not only the resistance change of the correction resistor caused by the temperature change of the pressure fluid, but also the resistance change of the correction resistor caused by the distortion of the membrane. However, it is possible to prevent further inclusion of errors due to the effects of external resistors.

Preferably, the correction resistor further includes a first conductive path and a second conductive path electrically connectable to one end of the correction resistor, and the external resistor is electrically connected to the second conductive path. and the release unit is a switch that switches the electrical connection destination of the correction resistor to either the first conductive path or the second conductive path. By switching the electrical connection destination of the correction resistor to the first conductive path by the switch, a state in which the correction resistor and the external resistor are not electrically connected is formed. Based on the output signal (temporary output signal), a process of measuring the temperature (temporary temperature) of the pressure fluid can be performed. Further, by switching the electrical connection destination of the correction resistor to the second conductive path by the switch, a state in which the correction resistor and the external resistor are electrically connected is formed. Based on the output signal of , a process of detecting the resistance change of the correction resistor caused by the distortion of the membrane can be executed.

Preferably, the device further includes a substrate portion to which the external substrate is fixed, the external substrate is arranged adjacent to the periphery of the membrane, and the external resistor formed on the external substrate is formed on the membrane. is arranged in the vicinity of the correction resistor. With such a configuration, it is possible to make the temperature conditions between the positions where the correction resistors are arranged and the positions where the external resistors are arranged to be the same. The resistance change of the resistor can be detected with high precision.

FIG. 1 is a schematic cross-sectional view of a pressure sensor according to a first embodiment of the invention. 2 is a schematic plan view of the pressure sensor shown in FIG. 1. FIG. 3 is a schematic plan view showing each configuration of the detection circuit, the temperature measurement circuit and the strain measurement circuit shown in FIG. 2. FIG. 4A is a circuit diagram showing a circuit configuration when a voltage dividing resistor is electrically connected to one end of the correction resistor shown in FIG. 3. FIG. 4B is a circuit diagram showing a circuit configuration when an external resistor is electrically connected to one end of the correction resistor shown in FIG. 3; FIG. FIG. 5A is a diagram showing the relationship between the temperature change of the pressure fluid and the voltage value of the output signal of the correction resistor in the circuit shown in FIG. 4B. FIG. 5B is a diagram showing the relationship between the distortion occurring in the membrane and the voltage value of the output signal of the correction resistor in the circuit shown in FIG. 4B. FIG. 6A is a circuit showing a state when a voltage-dividing resistor is electrically connected to one end of a correction resistor in a circuit configured such that the circuit shown in FIG. 4A and the circuit shown in FIG. 4B can be switched by a switch. It is a diagram. FIG. 6B is a circuit diagram showing a state when an external resistor is electrically connected to one end of the correction resistor in the circuit shown in FIG. 6A. FIG. 7 is a schematic plan view showing configurations of a detection circuit, a temperature measurement circuit, and a strain measurement circuit of the pressure sensor according to the second embodiment of the present invention. FIG. 8 is a circuit diagram showing the configuration of a bridge circuit composed of the correction resistor and a plurality of external resistors shown in FIG. FIG. 9A is a circuit diagram showing a state when a voltage dividing resistor is electrically connected to one end of the correction resistor. FIG. 9B is a circuit diagram showing a state when an external resistor is electrically connected to one end of the correction resistor in the circuit shown in FIG. 9A. 10A is a diagram showing the relationship between the temperature change of the pressure fluid and the voltage value of the output signal of the correction resistor in the circuit shown in FIG. 8. FIG. 10B is a diagram showing the relationship between the distortion occurring in the membrane and the voltage value of the output signal of the correction resistor in the circuit shown in FIG. 8. FIG. FIG. 11 is a schematic plan view showing configurations of a detection circuit, a temperature measurement circuit, and a strain measurement circuit of a pressure sensor according to a third embodiment of the present invention.

The present invention will be described below based on the embodiments shown in the drawings.

First Embodiment A pressure sensor 10 according to a first embodiment of the present invention is a pressure sensor that utilizes the piezoresistive effect (piezoresistive effect), and detects strain due to deformation of the membrane from changes in the resistance of a resistor. be. As shown in FIG. 1 , the pressure sensor 10 has a connecting member 12 , a holding member 14 , a substrate portion 16 , an external substrate 18 and a stem 20 .

The connection member 12 is for fixing the pressure sensor 10 to the object to be measured. A thread groove 12 a is formed on the outer peripheral surface of the connecting member 12 . The thread groove 12a has a shape that can be screwed into a thread groove formed in the object to be measured. Inside the connecting member 12, a channel 12b is formed which is used as a channel for pressure fluid. By fixing the pressure sensor 10 to the object to be measured via the thread groove 12a, the flow path 12b can be airtightly communicated with the pressure chamber to be measured.

The holding member 14 is for fixing the stem 20 to the connecting member 12 . The holding member 14 is arranged on the upper surface of the connecting member 12 and has a ring-shaped outer shape. A through hole is formed in the center of the restraining member 14, and the stem 20 can be inserted (arranged) therein. A portion of the stem 20 (a flange portion 21 described later) can be fixed between the holding member 14 and the connecting member 12 .

The stem 20 has a cylindrical outer shape with a bottom (upper base) and is provided at one end of the flow path 12 b in the connection member 12 . The stem 20 is made by machining a metal such as stainless steel or an alloy. The material of the stem 20 is not particularly limited as long as it causes appropriate elastic deformation.

The stem 20 has a flange portion 21, a membrane 22 and a side wall portion 23. The side wall portion 23 has a cylindrical outer shape. One end of the side wall portion 23 is closed with the membrane 22, while the other end of the side wall portion 23 is open. The flange portion 21 is provided on the opening side of the stem 20 and protrudes radially outward from an opening edge formed at the other end of the side wall portion 23 . By fixing the flange portion 21 so as to be sandwiched between the holding member 14 and the connecting member 12, the stem 20 is connected to the connecting member 12 while the opening of the stem 20 is airtightly connected to one end of the flow path 12b of the connecting member 12. It is possible to fix to

The membrane 22 is a portion to which the pressure to be measured is transmitted, and constitutes the upper bottom portion of the stem 20 . The membrane 22 is formed thinner than the other portions (side wall portion 23, etc.) of the stem 20, and generates deformation (distortion) according to the pressure transmitted from the flow path 12b (the pressure received from the pressure fluid). . The membrane 22 has an inner surface 22a that contacts the pressurized fluid and an outer surface 22b opposite to the inner surface 22a. The outer surface 22b of the membrane 22 is provided with a detection circuit 30, a temperature measurement circuit 41, electrodes 51 to 56, etc., which will be described later (see FIG. 3).

The substrate portion 16 is fixed to the upper surface of the holding member 14 and has a ring-shaped outer shape. A through hole is formed in the center of the substrate portion 16, and the stem 20 can be inserted (arranged) therein. Electrode portions 57 to 64 (FIG. 2) are formed on the substrate portion 16, and the electrode portions 57 to 62 of the substrate portion 16 and the electrode portions 51 to 56 on the membrane 22 are connected by wire bonding or the like. They are electrically connected via wiring 80 . Electrode portions 57 to 64 formed on the substrate portion 16 are electrically connected to, for example, a signal line, power supply line, ground, or the like.

The external substrate 18 is configured separately from the substrate portion 16, and is fixed to the upper surface of the substrate portion 16 with a fastener such as a screw 82 or an adhesive. A distortion measuring circuit 42 and electrodes 65 to 66 (FIG. 2) are provided on the upper surface of the external substrate 18, which will be described later. Examples of materials forming the external substrate 18 include stainless steel, copper alloys, aluminum alloys, and steel. Note that the external substrate 18 may be made of the same material as the stem 20 .

The thermal properties of the external substrate 18 are preferably similar (substantially the same) as the thermal properties of the membrane 22 . That is, the external substrate 18 is preferably made of a material having thermal properties similar to those of the membrane 22 . Thermal properties include, but are not limited to, thermal conductivity, specific heat, coefficient of thermal expansion, latent heat and melting temperature.

The external substrate 18 is preferably arranged adjacent to the membrane 22 on the outside (periphery) of the membrane 22 . As will be described later, in this embodiment, the external substrate 18 is provided with an external resistor Re, and the membrane 22 is provided with a correction resistor Rc. The external substrate 18 is located close to the membrane 22 (in particular, the position where the correction resistor Rc of the membrane 22 is provided) so that the temperature conditions (temperature environment) are the same with the position where the resistor Re is arranged. are placed as follows. For example, the external substrate 18 may be arranged along the outer circumference of the membrane 22 .

From the viewpoint of making the temperature conditions the same between the position where the correction resistor Rc is arranged and the position where the external resistor Re is arranged, the position (height) of the surface of the external substrate 18 in the Z-axis direction is preferably substantially equal to the position (height) of the surface of the membrane 22 in the Z-axis direction. From the viewpoint of making the position (height) of the surface of the external substrate 18 approximately equal to the position (height) of the surface of the membrane 22 , the position of the surface of the external substrate 18 in the Z-axis direction corresponds to the Z It is preferably between the axial position and the Z-axis position of the outer surface 22b of the membrane 22 .

As described above, the membrane 22 is provided with the detection circuit 30, the temperature measurement circuit 41, the electrode portions 51 to 56, and the like. These configurations will be described below with reference to FIGS. 2 and 3. FIG. As shown in FIG. 2, the detection circuit 30 has sensor resistors R1 to R4 and is formed in the strain generating region of the membrane 22 .

　In FIG. 3, the top view is a schematic cross-sectional view of the stem 20, and the bottom view is a schematic plan view of the stem 20. As shown in FIG. The strain generating region of the membrane 22 consists of a first strain region 24 that produces strain characteristics in a predetermined direction and a second strain region 26 that produces strain characteristics in the opposite direction to the first strain regions 24 . The first strained region 24 of the membrane 22 receives pressure (positive pressure) from the inner surface 22a and produces a negative strain -ε (compressive strain), while the second strained region 26 of the membrane 22 Upon receiving pressure (positive pressure) from the inner surface 22a, positive strain +ε (tensile strain) is generated. Thus, it is preferable that the distortion characteristics on the first distortion region 24 and the distortion characteristics on the second distortion region 26 are in mutually different directions (they have different signs and cancel each other out).

The first strained region 24 and the second strained region 26 are formed concentrically around the center O of the membrane 22, respectively. The second distorted region 26 is located at a predetermined distance from the center O of the membrane 22 in the radial direction and is formed at the center of the membrane 22 . The first distorted region 24 is formed outside (peripheral side) of the second distorted region 26 and located at a position a predetermined distance away from the second distorted region 26 in the radial direction of the membrane 22 . An outer edge 27 of membrane 22 is connected to side wall 23 of stem 20 .

The sensor resistors R1 to R4 constituting the detection circuit 30 are pressure detection elements, and are configured to generate strain according to the deformation of the membrane 22, and change the resistance value by the piezoresistive effect according to the amount of strain. ing.

The sensor resistors R1 to R4 are produced, for example, by patterning a conductive thin film (semiconductor thin film, metal thin film, etc.) made of a predetermined material into a meander shape, for example. The patterning of the conductive thin film is performed by fine processing or the like using semiconductor processing techniques such as laser processing and screen printing. The conductive thin film is formed on the membrane 22 with an insulating film interposed therebetween by a thin film method such as sputtering or vapor deposition. However, when the membrane 22 is made of an insulating material such as alumina and the outer surface 22b of the membrane 22 has insulating properties, a conductive thin film can be formed directly on the outer surface 22b of the membrane 22 without forming an insulating film. good too. As the conductive thin film, for example, a strain resistance film containing Cr and Al is exemplified.

The sensor resistor R1 and the sensor resistor R3 are formed in the first strain region 24 and arranged to face each other with the center O of the membrane 22 interposed therebetween. The sensor resistor R2 and the sensor resistor R4 are formed in the second strain region 26 and arranged to face each other with the center O of the membrane 22 interposed therebetween. The direction in which the sensor resistor R1 and the sensor resistor R3 face each other is substantially orthogonal to the direction in which the sensor resistor R2 and the sensor resistor R4 face each other. The arrangement of the sensor resistors R1 to R4 is not limited to the arrangement shown in the drawing, and may be changed as appropriate.

The detection circuit 30 is formed on the upper surface of the membrane 22 so as to straddle the first distorted region 24 and the second distorted region 26, and has an annular (elliptical) outer shape. The detection circuit 30 is a bridge circuit, and constitutes a Wheatstone bridge in this embodiment. However, the configuration of the detection circuit 30 is not limited to the illustrated configuration, and the detection circuit 30 may configure another bridge circuit.

In the detection circuit 30, the sensor resistor R1 and the sensor resistor R2 are connected via a connection point 71, the sensor resistor R1 and the sensor resistor R4 are connected via a connection point 72, and the sensor resistor R3 and The sensor resistor R4 is connected via a connection point 73, and the sensor resistor R2 and the sensor resistor R3 are connected via a connection point 74. FIG. That is, the sensor resistors R1-R4 are electrically and physically connected to each other via the connection points 71-74.

The connection point 71 is electrically connected to the electrode portion 51, the connection point 72 is electrically connected to the electrode portion 52, the connection point 73 is electrically connected to the electrode portion 53, and the connection point 74 is electrically connected to the electrode portion 54 .

The electrode portions 51 to 54 are produced by patterning a conductive thin film (semiconductor thin film, metal thin film, etc.) made of a predetermined material into a predetermined shape, for example, by the same method as the sensor resistors R1 to R4. . The same applies to electrode portions 55 and 56, which will be described later. Each of the electrode portions 51 to 54 is formed on the outer edge portion 27 of the membrane 22, but the positions of the electrode portions 51 to 54 are not limited to the illustrated positions. It may be formed at any position between.

Each of the connection points 71 to 74 and each of the electrode portions 51 to 54 are continuously connected by the conductive thin film patterned into the predetermined shape described above. However, each of the connection points 71 to 74 and each of the electrode portions 51 to 54 may be connected by wire bonding or the like.

As shown in FIG. 2, the electrode portion 51 is electrically connected to the electrode portion 57 formed on the substrate portion 16 by wire bonding or the like, and the electrode portion 52 is connected to the electrode portion 58 formed on the substrate portion 16 by wire. The electrode portion 53 is electrically connected to the electrode portion 59 formed on the substrate portion 16 by wire bonding or the like, and the electrode portion 54 is electrically connected to the electrode portion 59 formed on the substrate portion 16 . It is electrically connected to the portion 60 by wire bonding or the like. The electrode portions 57 to 60 are produced on the substrate portion 16 by, for example, the same method as the electrode portion 51 and the like. The same applies to electrode portions 61 to 64, which will be described later.

The electrode section 58 is electrically connected to, for example, a power supply line, and power (bias voltage) is supplied from the power supply line to the detection circuit 30 via the electrode section 58 and the electrode section 52 . The electrode section 60 is electrically connected to the ground, for example.

The electrode section 57 is connected to, for example, a control section (not shown) of the pressure sensor 10, and the voltage (V+) at the connection point 71 is output as a detection signal to the control section via the electrode section 57 and the electrode section 51. be. The electrode section 59 is connected to, for example, a control section (not shown) of the pressure sensor 10, and the voltage (V-) at the connection point 73 is output as a detection signal to the control section via the electrode section 59 and the electrode section 53. be done. Note that the control unit is configured by an IC such as an MCU, FPGA, or ASIC, for example.

The voltage value V+ of the detection signal output from the electrode portion 57 (electrode portion 51) and the voltage value V− of the detection signal output from the electrode portion 59 (electrode portion 53) are combined by a differential amplifier having a gain of A, for example. By utilizing and amplifying, it is possible to acquire the output voltage V from the detection circuit 30 and detect the fluid pressure acting on the membrane 22 based on the output voltage V. FIG.

By the way, since the resistance change of the sensor resistors R1 to R4 formed in the membrane 22 is dependent on temperature, the output signal of the detection circuit 30 (output voltage V described above) includes the resistance of the sensor resistors R1 to R4. Errors due to temperature dependence of changes may be included. That is, the output signal of the detection circuit 30 includes not only the resistance changes of the sensor resistors R1 to R4 caused by the strain of the membrane 22, but also the resistance changes of the sensor resistors R1 to R4 caused by temperature changes of the pressure fluid. may contain errors.

Therefore, the error caused by the temperature dependence of the resistance change of the sensor resistors R1 to R4 (resistance change of the sensor resistors R1 to R4 caused by the temperature change of the pressure fluid) is measured, and based on the value In order to perform temperature correction on the output signal of the detection circuit 30, the pressure sensor 10 is provided with a temperature measurement circuit 41, as shown in FIG. The configuration of the temperature measurement circuit 41 will be described below.

The temperature measurement circuit 41 is formed on the membrane 22 and has a correction resistor Rc. The correction resistor Rc is a resistor for detecting temperature, and changes the resistance value according to the temperature change of the pressurized fluid, for example. The correction resistor Rc is formed independently (not electrically connected) to the detection circuit 30, and is formed in the outer edge portion 27 of the membrane 22, which is relatively less susceptible to distortion of the membrane 22. preferably. This is to prevent the correction resistor Rc from changing its resistance value according to the distortion of the membrane.

However, at least part of the correction resistor Rc may be formed in the strain generation region of the membrane 22 that is relatively susceptible to the strain of the membrane 22 . As will be described later, in this embodiment, a circuit (distortion measuring circuit 42) capable of measuring the resistance change of the correction resistor Rc caused by the distortion of the membrane 22 is provided. This is because, even when the correction resistor Rc is arranged at a certain position, the resistance change of the correction resistor Rc caused by the temperature change of the pressure fluid can be specified accurately.

For example, at least part of the correction resistor Rc may be formed at an arbitrary position between the first strain region 24 and the outer edge portion 27. Alternatively, part of the correction resistor Rc may be formed at an arbitrary position between the first strain region 24 and the second strain region 26 .

The correction resistor Rc is fabricated by patterning a conductive thin film (semiconductor thin film, metal thin film, etc.) made of a predetermined material into a predetermined shape, for example, in the same manner as the sensor resistors R1 to R4. .

The extending direction of the correction resistor Rc is, when viewed as a whole, substantially aligned with, for example, the circumferential direction of the membrane 22 (the correction resistor Rc extends along the circumferential direction of the membrane 22 in a meandering shape). ). However, the extending direction of the correction resistor Rc is not limited to this, and the correction resistor Rc may extend radially along the radial direction of the membrane 22, for example.

As shown in FIG. 2 , one end of the correction resistor Rc is electrically and physically connected to the electrode section 55 formed on the membrane 22 , and the other end of the correction resistor Rc is connected to the membrane 22 . It is electrically and physically connected to the electrode portion 56 formed thereon. The electrode portion 56 is electrically connected to the electrode portion 62 formed on the substrate portion 16 by wire bonding or the like, and is electrically connected to the ground, for example.

The electrode portion 55 is electrically connected to the electrode portion 61 formed on the substrate portion 16 by wire bonding or the like. The electrode section 61 is electrically connected to, for example, a control section (not shown) of the pressure sensor 10, and the voltage (Vo) at the connection point 75 is converted into an output signal ( It is possible to output to the control section as a signal indicating the resistance change of the correction resistor Rc.

The connection point 75 can be electrically connected to a power supply line (not shown) via the first conductive path 75a. A voltage dividing resistor Rt (see FIG. 6A) is interposed between the power supply line and the connection point 75, and a bias voltage Vdd1 (FIG. 3) is applied to the temperature measuring circuit 41 (correction resistor Rc). supplied. The voltage dividing resistor Rt may be provided in a control unit such as an ASIC.

The connection point 75 can be electrically connected to the external resistor Re via the second conductive path 75b. An electrode portion 63 and an electrode portion 65 are provided between the external resistor Re and the connection point 75 .

At the position of the connection point 75, it is preferable to provide a releasing portion for releasing the electrical connection between one end of the correction resistor Rc and the external resistor Re. For example, as shown in FIGS. 6A and 6B, a switch 83 may be provided at the connection point 75 as a release portion. In this case, the switch 83 can switch the electrical connection destination of one end of the correction resistor Rc to the first conductive path 75a or the second conductive path 75b. Switching control of the switch 83 is performed by, for example, a control unit (not shown) of the pressure sensor 10 or the like.

As described above, when performing temperature correction on the output signal of the detection circuit 30, the output signal of the correction resistor Rc is output to the control section via the electrode section 61 (FIG. 2). At this time, the electrical connection between one end of the correction resistor Rc and the external resistor Re is released, and one end of the correction resistor Rc is electrically connected to the voltage dividing resistor Rt as shown in FIG. 6A. , the output signal of the correction resistor Rc is detected by the control unit to avoid interference with the external resistor Re (distortion measurement circuit 42), and the output signal of the correction resistor Rc is It is possible to prevent an error from being included due to the influence of the external resistor Re.

Note that the first conductive path 75 a and the second conductive path 75 b may be physically and electrically connected at the connection point 75 without installing the release portion described above at the connection point 75 . However, in this case, it is preferable to provide means for preventing interference between the circuit on the side of the first conductive path 75a and the circuit on the side of the second conductive path 75b.

When one end of the correction resistor Rc is electrically connected to the first conductive path 75a of the first conductive path 75a and the second conductive path 75b, the correction resistor Rc and the voltage dividing resistor Rt are electrically connected. are directly connected to form the circuit shown in FIG. 4A or FIG. 6A. In this circuit, the output voltage Vo at node 76 (corresponding to electrode portion 61 shown in FIG. 2) is equal to the voltage at node 75 shown in FIG. . The output voltage Vo is obtained by dividing the bias voltage Vdd1 supplied through the first conductive path 75a by the voltage dividing resistor Rt and the correcting resistor Rc.

With one end of the correction resistor Rc electrically connected to the first conductive path 75a, the output signal of the correction resistor Rc (the output voltage Vo of the electrode section 61) is transmitted through the electrode section 61 (FIG. 2). ), it is possible to measure resistance changes (pressure fluid temperature) of the sensor resistors R1 to R4 caused by temperature changes of the pressure fluid, based on the detected values. Therefore, temperature correction can be performed on the output signal of the detection circuit 30 based on this measured value. In this way, measuring the resistance change (temperature of the pressure fluid) of the sensor resistors R1 to R4 caused by the temperature change of the pressure fluid based on the detected value of the output signal of the correction resistor Rc is called “temperature measurement. called a mode.

By the way, as shown in FIG. 2, since the correction resistor Rc is formed on the membrane 22, the resistance change of the correction resistor Rc is affected by the distortion of the membrane 22 to some extent. That is, when the membrane 22 receives pressure from the pressurized fluid and is distorted, the correction resistor Rc changes its resistance value due to the influence of the distortion. Therefore, the output signal (the output voltage Vo shown in FIG. 4A or FIG. 6A) of the correction resistor Rc detected in the temperature measurement mode includes not only the resistance change caused by the temperature change of the pressure fluid, but also the distortion of the membrane 22. The error may include the resistance change due to Therefore, the output signal of the correction resistor Rc detected in the temperature measurement mode may not accurately reflect the resistance change (temperature of the pressure fluid) of the sensor resistors R1 to R4 caused by the temperature change of the pressure fluid. Therefore, even if temperature correction is performed on the output signal of the detection circuit 30 based on this output signal, there is a possibility that the accuracy of the temperature correction cannot be ensured.

In order to accurately obtain the resistance change of the correction resistor Rc (temperature of the pressure fluid) caused by the temperature change of the pressure fluid, the resistance change of the correction resistor Rc caused by the strain of the membrane 22 is measured, and the temperature It is necessary to remove the resistance change of the correction resistor Rc caused by the distortion of the membrane 22 from the output signal of the correction resistor Rc detected in the measurement mode. Therefore, in the present embodiment, the pressure sensor 10 is provided with the strain measuring circuit 42 in order to measure the resistance change of the correction resistor Rc caused by the strain of the membrane 22 . The configuration of the distortion measuring circuit 42 will be described below.

The strain measurement circuit 42 is formed on the external substrate 18 and has an external resistor Re. The external resistor Re is fabricated by patterning a conductive thin film (semiconductor thin film, metal thin film, etc.) made of a predetermined material into a predetermined shape, for example, in the same manner as the correction resistor Rc. Unlike the correction resistor Rc, the external resistor Re is not formed on the membrane 22, and thus is not affected by distortion. Therefore, the external resistor Re does not substantially change in resistance due to strain, but only changes in resistance due to temperature.

One end of the external resistor Re is electrically and physically connected to an electrode portion 65 formed on the external substrate 18 . The electrode portion 65 is electrically connected to the electrode portion 63 formed on the substrate portion 16 by wire bonding or the like. The electrode portion 63 is electrically connected to the second conductive path 75b. For example, as shown in FIG. 6B, the switch 83 switches the electrical connection destination of one end of the correction resistor Rc to the second conductive path 75b, thereby connecting the external resistor Re to one end of the correction resistor Rc. electrically connected.

As shown in FIG. 2, the other end of the external resistor Re is electrically and physically connected to an electrode portion 66 formed on the external substrate 18. The electrode portion 66 is electrically connected to the electrode portion 64 formed on the substrate portion 16 by wire bonding or the like. The electrode section 66 is electrically connected to, for example, a power supply line, and a bias voltage Vdd2 (FIG. 3) is supplied from the power supply line to the distortion measuring circuit 42 via the electrode sections 64 and 66. be done.

When one end of the correction resistor Rc is electrically connected to the second conductive path 75b of the first conductive path 75a and the second conductive path 75b, the correction resistor Rc and the external resistor Re are electrically connected. are directly connected to form the circuit shown in FIG. 4B or FIG. 6B. In the circuit shown in FIG. 6B, the switch 83 can switch the electrical connection destination of one end of the correction resistor Rc from the first conductive path 75a to the second conductive path 75b.

In this circuit, the output voltage Vo at node 76 (corresponding to electrode portion 61 shown in FIG. 2) is equal to the voltage at node 75 shown in FIG. . The output voltage Vo is obtained by dividing the bias voltage Vdd2 supplied through the second conductive path 75b by the external resistor Re and the correction resistor Rc, and is expressed by the following formula (1).

Here, when a temperature change ΔT occurs in the correction resistor Rc due to a temperature change in the pressure fluid, and a temperature change ΔT also occurs in the external resistor Re, the correction resistor Rc after the temperature change The output voltage Vo' is represented by the following formula (2). In equation (2), TCR is the temperature resistance coefficient of the correction resistor Rc and the external resistor Re.

As shown in Equation (2), when the temperature of the correction resistor Rc changes by ΔT, the resistance of the correction resistor Rc changes by ΔRc (ΔRc=Rc·TCR·ΔT). Further, when the temperature of the external resistor Re changes by ΔT, the resistance of the external resistor Re changes by ΔRe (ΔRe=Re·TCR·ΔT). However, when resistance changes ΔRc and ΔRe occur in both the correction resistor Rc and the external resistor Re, as shown in Equation (2), the resistance change rate (1+TCR·ΔT) of the correction resistor Rc and Since the resistance change rate (1+TCR·ΔT) of the composite resistor composed of the correction resistor Rc and the external resistor Re is equal, these are canceled out, and as a result, the output voltage Vo′ after the temperature change is is expressed by the same formula as the output voltage Vo of . In other words, as shown in FIG. 5A, the output voltage Vo does not change with changes in temperature and is always a constant value.

On the other hand, when strain ε occurs in the correction resistor Rc due to the strain of the membrane 22, the output voltage Vo′ of the correction resistor Rc after the occurrence of the strain is represented by the following equation (3). . In equation (3), k is the sensitivity of the correction resistor Rc.

As shown in Equation (3), when the strain applied to the correction resistor Rc changes by ε, the correction resistor Rc changes resistance by ΔRc (ΔRc=k·ε·Rc). As is clear from Equation (3), the output voltage Vo' is a function with the magnitude of distortion ε as a variable. Therefore, as shown in FIG. 5B, the output voltage Vo' changes by an amount corresponding to the magnitude of ε.

That is, in the state where the correction resistor Rc and the external resistor Re are electrically connected (the state where the circuit shown in FIG. 4B is formed), the resistance of the correction resistor Rc caused by the temperature change of the pressure fluid The change does not appear as a change in the output voltage Vo (see FIG. 5A), and the change in the output voltage Vo of the correction resistor Rc always represents the resistance change of the correction resistor Rc caused by the strain of the membrane 22. becomes. Therefore, by detecting the output voltage Vo, the resistance change of the correction resistor Rc caused by the strain of the membrane 22 can be measured. Thus, measuring the resistance change of the correction resistor Rc caused by the strain of the membrane 22 based on the detected value of the output signal of the correction resistor Rc is called "distortion measurement mode".

As described above, the output signal of the correction resistor Rc detected in the temperature measurement mode includes the correction due to the distortion of the membrane 22 in addition to the resistance change of the correction resistor Rc caused by the temperature change of the pressure fluid. In some cases, the resistance change of the resistor Rc is included. On the other hand, the output signal of the correction resistor Rc detected in the strain measurement mode theoretically contains only the resistance change of the correction resistor Rc caused by the strain of the membrane 22 . Therefore, by taking the difference between the detected value of the output signal of the correction resistor Rc detected in the temperature measurement mode and the detected value of the output signal of the correction resistor Rc detected in the strain measurement mode, the former output signal The resistance change (error) due to the strain of the membrane 22 can be removed from the detected value of .

As a result, from the output signal of the correction resistor Rc detected in the temperature measurement mode, only the resistance change of the correction resistor Rc caused by the temperature change of the pressure fluid can be accurately specified (that is, the true value of the pressure fluid). temperature), and an accurate temperature correction can be made to the output signal of the detection circuit 30 .

Here, in order for the formula (2) to hold, the resistance change rate (1+TCR·ΔT) of the correction resistor Rc and the resistance change rate ( 1+TCR·ΔT) are substantially equal, that is, the TCR of the correction resistor Rc and the TCR of the external resistor Re are substantially equal, and the temperature change ΔT of the correction resistor Rc and the temperature change ΔT of the external resistor Re are substantially equal. It is assumed that the temperature change ΔT is substantially equal.

Therefore, in order to satisfy the above premise, the material constituting the external resistor Re should be the same material as the material constituting the correction resistor Rc, or a material having temperature characteristics (temperature coefficient of resistance, etc.) similar to that of the correction resistor Rc. is preferred. For example, the difference between the TCR of the external resistor Re and the TCR of the correction resistor Rc is preferably ±100 ppm or less.

Also, as shown in FIG. 2, the external resistor Re formed on the external substrate 18 is preferably arranged in the vicinity of the correction resistor Rc formed on the membrane 22 . In this case, it is possible to make the same temperature condition between the position where the external resistor Re is arranged and the position where the correction resistor Rc is arranged. Therefore, the temperature change ΔT of the correction resistor Rc and the temperature change ΔT of the external resistor Re become substantially equal, and the resistance change of the correction resistor Rc caused by the strain of the membrane 22 can be detected with high accuracy. .

In addition, by forming the external substrate 18 and the membrane 22 from materials having similar thermal characteristics, the temperature condition between the position where the external resistor Re is arranged and the position where the correction resistor Rc is arranged will vary. can be made the same. Therefore, the external resistor Re and the correction resistor Rc undergo similar temperature changes, and the output signal of the correction resistor Rc contains an error due to the difference in temperature change between the resistors. can be prevented, and the resistance change of the correction resistor Rc caused by the distortion of the membrane 22 can be detected with high accuracy.

As described above, the pressure sensor 10 according to the present embodiment can accurately detect the temperature of the pressure fluid, and based on the temperature information, the error contained in the output signal of the detection circuit 30 (each error caused by the temperature dependence of the resistance change of the sensor resistors R1 to R4) can be accurately corrected. In addition, since the resistance change of the correction resistor Rc caused by the distortion of the membrane 22 can be removed from the detected value of the output signal detected in the temperature measurement mode, the correction resistor Rc is placed in the distortion generation region of the membrane 22. There is no problem even if it is formed, and it is possible to favorably reduce the size of the pressure sensor 10 or improve the accuracy of temperature measurement.

Second Embodiment Next, the construction of a pressure sensor 10A according to a second embodiment of the present invention will be described. In the drawings, components common to the pressure sensor 10 of the first embodiment are denoted by common reference numerals, and descriptions thereof are omitted.

As shown in FIG. 7, the pressure sensor 10A has three external substrates 18_1-18_3 and three external resistors Re1-Re3. An external resistor Re1 is formed on the external substrate 18_1, an external resistor Re2 is formed on the external substrate 18_2, and an external resistor Re3 is formed on the external substrate 18_3.

The three external substrates 18_1 to 18_3 are configured separately and are arranged at predetermined intervals from each other. The external substrates 18_1 to 18_3 are preferably arranged close to each other from the viewpoint of making the temperature conditions (temperature environments) of the external resistors Re1 to Re3 the same.

The three external substrates 18_1 to 18_3 are provided with the membrane 22 (particularly, the membrane 22 (especially, the membrane 22) is preferably arranged close to the position where the correction resistor Rc is provided. For example, the external substrates 18_1 to 18_3 may be arranged along the outer circumference of the membrane 22 .

From the viewpoint of making these thermal characteristics similar, the external substrates 18_1 to 18_3 are preferably made of substrates made of materials having similar thermal characteristics. In addition, from the viewpoint of making the thermal characteristics of these external substrates 18_1 to 18_3 the same, it is preferable that the external substrates 18_1 to 18_3 be formed of substrates having the same shape, size, or height. The positions (heights) of the surfaces of the external substrates 18_1 to 18_3 are preferably substantially equal to each other, and preferably substantially equal to the position (height) of the surface of the membrane 22 . That is, the Z-axis direction positions of the surfaces of the external substrates 18_1 to 18_3 are between the Z-axis direction positions of the inner surface 22a (FIG. 1) of the membrane 22 and the Z-axis direction positions of the outer surface 22b of the membrane 22. is preferred.

The external resistors Re1 to Re3 may be resistors similar to the external resistor Re in the first embodiment. Alternatively, the external resistors Re1 to Re3 may be resistors having a shape, size or resistance value different from that of the external resistor Re in the first embodiment. Also, the external resistors Re1 to Re3 may be resistors having the same shape, size or resistance value. Alternatively, at least one of the external resistors Re1 to Re3 may be a resistor having a shape, size or resistance value different from that of the other resistors.

From the viewpoint of making the temperature characteristics of the external resistors Re1 to Re3 similar, it is preferable that the materials constituting the external resistors Re1 to Re3 be the same material or materials with similar temperature characteristics. In this case, for example, when the temperature environment of the external resistors Re1 to Re3 changes according to the temperature change of the pressure fluid, it is possible to cause the same temperature change ΔT to occur in the external resistors Re1 to Re3. becomes.

The external resistors Re1 to Re3 are electrically connected by wire bonding or wiring on the substrate portion 16 via electrodes formed on the external substrates 18_1 to 18_3 and the substrate portion 16 (FIG. 2).

More specifically, the electrode portion 65 electrically connected to one end of the external resistor Re1 is electrically connected to the connection point 75, and the electrode portion 65 electrically connected to the other end of the external resistor Re1. The portion 66 is electrically connected to an electrode portion 68 electrically connected to the other end of the external resistor Re2. The electrode portion 67 electrically connected to one end of the external resistor Re2 is electrically connected to the electrode portion 70 electrically connected to the other end of the external resistor Re3. The electrode portion 69 electrically connected to one end of the external resistor Re3 is electrically connected to the connection point 79 . The connection point 79 is electrically connected to the electrode portion 56 formed at the other end of the correction resistor Rc.

A connection point 77 electrically connected to the electrode portion 66 and the electrode portion 68 is electrically connected to a power supply line, and a connection point 79 electrically connected to the electrode portion 56 and the electrode portion 69. is electrically connected to ground. A connection point 76 electrically connected to the electrode section 65 and the electrode section 55 is connected to a control section (not shown) of the pressure sensor 10A, and the voltage V ₊ at the connection point 76 (an external intermediate potential between the resistor Re1 and the correction resistor Rc) is output to the control section as a detection signal. A connection point 78 electrically connected to the electrode section 67 and the electrode section 70 is connected to a control section (not shown) of the pressure sensor 10A, and the voltage V ₋ at the connection point 78 (an external intermediate potential between the resistor Re2 and the external resistor Re3) is output to the controller as a detection signal.

As shown in FIG. 8, the correction resistor Rc and the plurality of external resistors Re1 _to Re3 form a bridge circuit. _- is the output voltage Vo2 (Vo2=V ₊ -V _- ) of the output signal of the correction resistor Rc.

As shown in FIGS. 9A and 9B, a switch 83 (release section) may be provided at the position of the connection point 75 . As shown in FIG. 9A, when the switch 83 is electrically connected to the first conductive path 75a, the temperature measurement mode is entered, and a series circuit is formed by the voltage dividing resistor Rt and the correction resistor Rc. The output voltage Vo1 at the connection point 76 is output to the control section (not shown) of the pressure sensor 10A as the output signal of the correction resistor Rc. The detected value of the output voltage Vo1 mainly indicates the resistance change of the correction resistor Rc caused by the temperature change of the pressure fluid (the output voltage Vo1 includes the correction resistor Rc (including the change in resistance).

As shown in FIG. 9B, when the switch 83 is electrically connected to the second conductive path 75b, the strain measurement mode is entered, and a bridge circuit is formed by the correction resistor Rc and the external resistors Re1 to Re3. , the output voltage V ₊ at the connection point 76 and the output voltage V _- at the connection point 78 are output to the control section (not shown) of the pressure sensor 10A as the output signal of the correction resistor Rc (bridge circuit). The controller calculates the difference between the output voltage V ₊ and the output voltage V _- as the output voltage (differential output) Vo2. The detected value of the output voltage Vo2 indicates the resistance change of the correction resistor Rc caused by the strain of the membrane 22, and is a function with the magnitude of strain ε as a variable, as shown in FIG. 10B. In addition, as shown in FIG. 10A, the output voltage Vo2 does not change with respect to the temperature change (ΔT), and is always a constant value.

Therefore, by removing the output signal value (output voltage Vo2) detected in the strain measurement mode from the output signal value (output voltage Vo1) detected in the temperature measurement mode, the output signal detected in the temperature measurement mode is It is possible to remove the resistance change of the correction resistor Rc caused by the distortion of the membrane 22 from the detected value. As a result, it is possible to accurately detect the temperature of the pressure fluid, and based on the temperature information, the error contained in the output signal of the detection circuit 30 (the temperature dependence of the resistance change of each sensor resistor R1 to R4) resulting error) can be accurately corrected.

Thus, the same effects as in the first embodiment can be obtained in this embodiment as well. Further, since the output signal of the correction resistor Rc can be obtained as a differential output of the bridge circuit, it is possible to remove the bias voltage from the output signal (output voltage) as shown in FIG. 10B. The resistance change of the correction resistor Rc caused by the distortion of the membrane 22 can be read in detail. Moreover, the influence of noise superimposed on the output signal of the correction resistor Rc can be reduced.

In addition, in this embodiment, by forming the external resistors Re1 to Re3 on the external substrates 18_1 to 18_3, respectively, by appropriately adjusting the installation positions of the external substrates 18_1 to 18_3, the arrangement of the external resistors Re1 to Re3 can be achieved. can be freely adjusted, and the degree of freedom in arranging the external resistors Re1 to Re3 can be increased.

Third Embodiment Next, the construction of a pressure sensor 10B according to a third embodiment of the present invention will be described. In the drawings, components common to the pressure sensor 10A of the second embodiment are denoted by common reference numerals, and descriptions thereof are omitted.

As shown in FIG. 11, the pressure sensor 10B of the present embodiment differs from the pressure sensor 10A of the second embodiment in that all of the external resistors Re1 to Re3 are formed on a single external substrate 18. different. The external resistors Re1 to Re3 may be formed on the external substrate 18 in an arrangement as shown. Alternatively, they may be formed on the external substrate 18 so as to be arranged in a line. Although detailed illustration is omitted, a release portion such as a switch 83 (FIGS. 9A and 9B) may be provided at the position of the connection point 75 .

Also in this embodiment, the same effects as in the second embodiment can be obtained. In addition, in this embodiment, since the external resistors Re1 to Re3 are formed on the same substrate, the temperature conditions at the positions where the external resistors Re1 to Re3 are arranged are the same. Therefore, the external resistors Re1 to Re3 undergo similar temperature changes, and the output signal of the correction resistor Rc contains an error caused by the difference in temperature change among the external resistors Re1 to Re3. can be prevented.

It should be noted that the present invention is not limited to the above-described embodiments, and can be modified in various ways within the scope of the present invention.

In each of the above embodiments, the voltage dividing resistor Rt shown in FIG. 4A is not essential and may be omitted. In this case, in the temperature measurement mode, the output signal of the correction resistor Rc is obtained by connecting one end of the correction resistor Rc to a current source and supplying a current to the correction resistor Rc through the current source. You may

In the first embodiment, the position of the external substrate 18 is not limited to the position shown in FIG. 1, and may be changed as appropriate. For example, the external substrate 18 may be positioned adjacent to the membrane 22 .

In the above second embodiment, the number of external substrates may be two. In this case, one of the external resistors Re1 to Re3 may be formed on one external substrate, and the remaining two external resistors may be formed on the other external substrate.

DESCRIPTION OF SYMBOLS 10, 10A, 10B... Pressure sensor 12... Connection member 12a... Thread groove 12b... Flow path 14... Control member 16... Substrate part 18, 18_1 to 18_3... External substrate 20... Stem 21... Flange part 22... Membrane 22a... Inner surface 22b Outer surface 23 Side wall portion 24 First strain region 26 Second strain region 30 Detection circuit 41 Temperature measurement circuit 42 Strain measurement circuit 51 to 70 Electrode portion 71 to 79 Connection point 80 Connection wiring 82...Screw R1 to R4...Sensor resistor Rc...Correction resistor Re, Re1 to Re3...External resistor

Claims (7)

1. a membrane that deforms in response to pressure;
   a plurality of sensor resistors formed on the membrane and constituting a detection circuit;
   a correction resistor formed on the membrane for detecting temperature;
   an external resistor formed on an external substrate different from the membrane and electrically connectable to one end of the correction resistor.
2. The external substrate is composed of a plurality of external substrates,
   The external resistor consists of a plurality of external resistors,
   Each of the plurality of external substrates is formed with each of the plurality of external resistors,
   2. The pressure sensor according to claim 1, wherein said correction resistor and said plurality of external resistors form a bridge circuit.
3. The external resistor consists of a plurality of external resistors,
   A plurality of the external resistors are formed on the external substrate,
   2. The pressure sensor according to claim 1, wherein said correction resistor and said plurality of external resistors form a bridge circuit.
4. The pressure sensor according to any one of claims 1 to 3, wherein the external substrate and the membrane are made of materials having similar thermal properties.
5. The pressure sensor according to any one of claims 1 to 4, further comprising a releasing portion for releasing electrical connection between the correction resistor and the external resistor.
6. further comprising a first conductive path and a second conductive path electrically connectable to one end of the correction resistor;
   The external resistor is electrically connected to the second conductive path,
   6. The pressure sensor according to claim 5, wherein the releasing portion comprises a switch that switches the electrical connection destination of the correction resistor to either the first conductive path or the second conductive path.
7. further comprising a board portion to which the external board is fixed;
   The external substrate is arranged adjacent to the periphery of the membrane,
   7. The pressure sensor according to claim 1, wherein said external resistor formed on said external substrate is arranged near said correction resistor formed on said membrane.

Images