CN114689221A - Absolute pressure type piezoresistive sensing system and self-testing method thereof - Google Patents
Absolute pressure type piezoresistive sensing system and self-testing method thereof Download PDFInfo
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- CN114689221A CN114689221A CN202011616563.5A CN202011616563A CN114689221A CN 114689221 A CN114689221 A CN 114689221A CN 202011616563 A CN202011616563 A CN 202011616563A CN 114689221 A CN114689221 A CN 114689221A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L25/00—Testing or calibrating of apparatus for measuring force, torque, work, mechanical power, or mechanical efficiency
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L27/00—Testing or calibrating of apparatus for measuring fluid pressure
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
Abstract
The invention relates to the technical field of piezoresistive sensors, in particular to an absolute pressure type piezoresistive sensing system and a self-testing method thereof. In this sensing system, the piezoresistive sensing module includes: the protective layer, the thin film layer, the silicon substrate layer and the glass layer are stacked; a cavity structure is arranged in the silicon substrate layer; one side of the film layer close to the protective layer is provided with a pressure resistance strip; a metal electrode is arranged on one side of the protective layer away from the thin film layer; the metal electrode is electrically connected with the piezoresistive strips; the metal plate is arranged on one side of the protective layer far away from the thin film layer; the alternating magnetic field generating device is arranged on one side of the glass layer far away from the silicon substrate layer; the signal input end of the signal processing circuit is connected with the signal output end of the piezoresistive sensing module; the signal processing circuit is respectively connected with the alternating magnetic field generating device and the piezoresistive sensing module in a power supply mode. The invention provides the pressure self-testing function of the absolute pressure type piezoresistive sensing system, saves the processes of building off-chip testing equipment and repeatedly disassembling and testing, and improves the detection efficiency of the absolute pressure type piezoresistive sensing system.
Description
Technical Field
The invention relates to the technical field of piezoresistive sensors, in particular to an absolute pressure type piezoresistive sensing system and a self-testing method thereof.
Background
The MEMS (Micro Electro Mechanical System) technology is developed by combining with other processing technologies on the basis of the microelectronic manufacturing process, and is frequently applied to the high-tech field requiring small size, high precision, high reliability and low power consumption.
The absolute pressure type piezoresistive sensing system belongs to a piezoresistive sensor, can realize measurement of external air pressure, strain and pressure and the like by utilizing the piezoresistive effect of a semiconductor material, converts the external pressure value into an electric signal to be output, and is widely applied to control systems in the fields of water conservancy and hydropower, railway traffic, aerospace, petrochemical industry, electric power, ship industry and the like.
The absolute pressure type piezoresistive sensing system needs to be used and detected regularly, complex physical excitation is carried out on the absolute pressure type piezoresistive sensing system by high-precision off-chip testing equipment generally, but the existing off-chip testing equipment is large and expensive testing equipment generally, so that the cost of the whole testing process is high, time and labor are wasted, and the efficiency is not high.
Therefore, how to improve the detection efficiency of the absolute pressure type piezoresistive sensing system is a technical problem which needs to be solved urgently at present.
Disclosure of Invention
The invention aims to provide an absolute pressure type piezoresistive sensing system and a self-testing method thereof, so that the detection efficiency of the absolute pressure type piezoresistive sensing system is improved.
In order to achieve the above object, the embodiments of the present invention provide the following solutions:
in a first aspect, an embodiment of the present invention provides an absolute pressure type piezoresistive sensing system, including: the piezoresistive sensing module comprises a metal plate, a piezoresistive sensing module, an alternating magnetic field generating device and a signal processing circuit;
the piezoresistive sensing module comprises: the protective layer, the thin film layer, the silicon substrate layer and the glass layer are stacked; a cavity structure is arranged in the silicon substrate layer; one side of the thin film layer, which is close to the protective layer, is provided with a piezoresistive strip; a metal electrode is arranged on one side of the protective layer, which is far away from the thin film layer; the metal electrode is electrically connected with the piezoresistive strip;
the metal plate is arranged on one side of the protective layer, which is far away from the thin film layer;
the alternating magnetic field generating device is arranged on one side of the glass layer far away from the silicon substrate layer;
the signal input end of the signal processing circuit is connected with the signal output end of the piezoresistive sensing module; and the signal processing circuit is respectively connected with the alternating magnetic field generating device and the piezoresistive sensing module in a power supply manner.
In a possible embodiment, the metal plate is a metal disc made of aluminum, gold or silver.
In one possible embodiment, the metal plate is of an equal thickness disc-like structure.
In one possible embodiment, the protective layer is a silicon nitride layer or a silicon dioxide layer.
In one possible embodiment, the alternating magnetic field generating device comprises a fixed frame and a solenoid coil; the solenoid coil is arranged in the fixing frame.
In a possible embodiment, the solenoid is located in the center of the side of the glass layer facing away from the silicon substrate layer.
In one possible embodiment, the solenoid is a copper wire solenoid.
In one possible embodiment, the signal processing circuit comprises a processor, a controllable switch, a digital-to-analog converter, an analog-to-digital converter, a temperature compensation circuit, and a differential amplifier;
the power supply output end of the processor is connected with the first switch input end of the controllable switch through the digital-to-analog converter; the control end of the processor is connected with the switch control end of the controllable switch;
the first switch output end of the controllable switch is grounded through the solenoid coil;
the second switch output end of the controllable switch is connected with the first bridge input end of the Wheatstone bridge; a second bridge input terminal of the Wheatstone bridge is grounded; a first bridge output end of the Wheatstone bridge is connected with a first input end of the differential amplifier through the temperature compensation circuit; a second bridge output end of the Wheatstone bridge is connected with a second input end of the differential amplifier; the output end of the differential amplifier is connected with the signal input end of the processor through the analog-to-digital converter; wherein the Wheatstone bridge is formed by connecting the piezoresistive strips.
In one possible embodiment, the temperature compensation circuit comprises a thermistor and a non-thermistor with a temperature coefficient less than a set threshold; the thermistor and the non-thermistor are connected in parallel.
In a second aspect, an embodiment of the present invention provides a self-test method for an absolute pressure type piezoresistive sensing system according to any one of the first aspects, where the method includes:
supplying power to the metal plate by using alternating current with a set frequency so as to enable the metal plate to generate eddy current electromagnetic force towards the piezoresistive sensing module;
acquiring a pressure sensing signal output by the piezoresistive sensing module under the action of the eddy current electromagnetic force; the pressure sensing signal is a voltage value representing the resistance variation of the piezoresistive sensing module;
and obtaining the dynamic characteristic of the piezoresistive sensing module according to the pressure sensing signal.
Compared with the prior art, the invention has the following advantages and beneficial effects:
in the invention, a metal plate is arranged on one side of a piezoresistive sensing module, an alternating magnetic field generating device is arranged on the other side of the piezoresistive sensing module, because the alternating magnetic field generating device can form the alternating magnetic field near the piezoresistive sensing module at one side close to the glass layer, because of the eddy current effect, the metal plate can generate eddy current electromagnetic force with the direction changing alternately in the alternating magnetic field, so that the absolute pressure type piezoresistive sensing system can carry out pressure self-test according to the eddy current electromagnetic force, the processes of building off-chip test equipment and repeatedly disassembling and testing are omitted, the detection efficiency of the absolute pressure type piezoresistive sensing system is improved, the sensor can realize the self-test of the function without depending on the traditional test equipment, and simultaneously after the sensor is put into use for a period of time, on the basis of not needing to dismantle the sensor, still can realize the test to sensor performance.
Drawings
In order to more clearly illustrate the embodiments of the present specification or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present specification, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an absolute pressure type piezoresistive sensing system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an alternating dynamic magnetic field distribution provided by an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a metal plate according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a connection of a signal processing circuit according to an embodiment of the present invention;
FIG. 5 is a flow chart of a method for self-testing an absolute pressure piezoresistive sensing system according to an embodiment of the present invention.
Description of reference numerals: the piezoresistive sensor module comprises a metal plate 1, a piezoresistive sensing module 2, a protective layer 21, a thin film layer 22, a piezoresistive strip 221, a metal electrode 222, a silicon substrate layer 23, a cavity structure 231, a glass layer 24, an alternating magnetic field generating device 3, a signal processing circuit 4, a processor 41, a controllable switch 42, a digital-to-analog converter 43, an analog-to-digital converter 44, a temperature compensating circuit 45 and a differential amplifier 46.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments, and all other embodiments obtained by those skilled in the art based on the embodiments of the present invention belong to the scope of protection of the embodiments of the present invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of an embodiment of the structure, which specifically includes: the piezoresistive pressure sensing sensor comprises a metal plate 1, a piezoresistive pressure sensing module 2, an alternating magnetic field generating device 3 and a signal processing circuit 4.
Specifically, a silicon nitride material or a silicon dioxide material may be used to make the protective layer 21, and the thin film layer 22 and the silicon substrate layer 23 may be made of silicon wafers of the same material, or of course, a deep silicon etching process may be adopted to form the cavity structure 231 on one side of the silicon substrate material, and the thin film layer 22 is correspondingly formed on the other side of the silicon substrate material. The glass layer 24 and the silicon substrate layer 23 can be connected by a bonding process.
The movable thin film layer 22 is arranged on the cavity structure 231 in the absolute pressure type piezoresistive sensing system, the surface of the thin film layer 22 forms the piezoresistive strips 221 through an ion implantation technology, then the bottom of the silicon substrate layer 23 is bonded with glass to form a vacuum closed cavity, when the top end of the thin film is subjected to external applied pressure, due to ion implantation, the piezoresistive effect of the piezoresistive strips 221 on the surface of the thin film layer 22 is amplified, the resistivity of the piezoresistive strips 221 changes, the four piezoresistive strips 221 communicated with the surface of the thin film form a Wheatstone bridge, the pressure value borne by the surface of the thin film can be calculated by measuring the output voltage value of the bridge, and the purpose of measuring absolute pressure is achieved.
The process of calculating the pressure-sensitive signal of the pressure-insulated piezoresistive sensing system in the following embodiment will be briefly described. The piezoresistive sensing module 2 in this embodiment is mainly used for pressure detection based on the piezoresistive effect of the material. The piezoresistive effect is a physical effect that, for a metal or a semiconductor material, if pressure or tension is applied along a certain crystal plane of the metal or the semiconductor material, the volume of the semiconductor changes, the inside of a crystal lattice of the semiconductor is distorted, an energy band changes, the mobility and the concentration of majority carriers in a conduction band change, and the resistivity changes significantly.
The change in resistivity (Δ ρ/ρ) can be expressed as the product of the piezoresistive coefficient and the stress experienced, and is given by the formula:
wherein, pilIs the longitudinal piezoresistive coefficient, pitIs the transverse piezoresistive coefficient, σlFor longitudinal stress, σtIs a transverse stress.
Piezoresistive material (i.e. piezoresistive strips 221) placed along axis <100>, with specific piezoresistive coefficients:
πl,＜100＞＝π11,πt,＜100＞＝π12。
the piezoresistive material (i.e., piezoresistive strip 221) is placed along axis <110> with specific piezoresistive coefficients:
and the change amount (dR/R) of the resistance value of the material is as follows:
wherein the content of the first and second substances,
the resistance value of the piezoresistive material is changed due to the size change factor,
is the resistance value change of the piezoresistive material caused by piezoresistive effect.
Because the temperature change is not large and the size change of the piezoresistive material is very weak in the process of the resistance value change of the piezoresistive material caused by the piezoresistive effect, the resistance value change of the material caused by the piezoresistive effect is much larger than the resistance value change caused by the geometric size change, and therefore, if the size change factor of the material is not considered, the resistance change quantity can be expressed by the following formula:
after the resistance variable quantity is obtained, the external pressure can be represented, and absolute pressure detection is realized.
The alternating magnetic field generating device 3 is arranged on the side of the glass layer 24 far away from the silicon substrate layer 23.
Specifically, the direction of the magnetic induction line that can be generated by the alternating magnetic field generating device 3 at the center position near one side of the glass layer 24 is perpendicular to the glass layer 24, as shown in fig. 2, which is a schematic diagram of the distribution of the alternating dynamic magnetic field provided in this embodiment.
Specifically, the alternating magnetic field generating device 3 comprises a fixed frame and a solenoid coil; the solenoid is arranged in the holder in a central position on the side of the glass layer 24 remote from the silicon substrate layer 23. The coil may be a metal wire coil such as a copper wire coil.
The metal plate 1 is arranged on the side of the protective layer 21 far away from the film layer 22, and when alternating current which is harmonious and alternating passes through the solenoid coil, an alternating magnetic field is generated around the piezoresistive sensing module 2, the alternating magnetic field acts on the metal disc above the sensitive film, and eddy current induced in the metal disc generates eddy current electromagnetic force in the magnetic field due to electromagnetic induction. The eddy current electromagnetic force also varies up and down due to the alternating magnetic field. Since the eddy current electromagnetic force is related to the frequency of the alternating current, the present embodiment can apply a controllable alternating pressure to the piezoresistive sensing module 2 through the metal plate 1 to perform a pressure self-test of the absolute pressure type piezoresistive sensing system.
Specifically, the metal plate 1 may be an aluminum metal plate, a gold metal plate, or a silver metal plate.
In order to enable the eddy current electromagnetic force generated by the metal plate 1 to act on the piezoresistive sensing module 2 uniformly, the present embodiment further provides a structure of the metal plate 1, as shown in fig. 3, the metal plate 1 is disposed in the middle of a wheatstone bridge composed of 4 piezoresistive strips 221, and is in an equal-thickness disk-shaped structure.
The signal processing circuit 4 comprises a processor 41, a controllable switch 42, a digital-to-analog converter 43, an analog-to-digital converter 44, a temperature compensation circuit 45 and a differential amplifier 46.
As shown in fig. 4, which is a connection schematic diagram of the signal processing circuit 4 provided in this embodiment, specifically, a power supply output end of the processor 41 is connected to a first switch input end of the controllable switch 42 through the digital-to-analog converter 43; the control end of the processor 41 is connected with the switch control end of the controllable switch 42; the first switch output of the controllable switch 42 is grounded through a solenoid; a second switch output of the controllable switch 42 is connected to a first bridge input of the wheatstone bridge; the second bridge input end of the Wheatstone bridge is grounded; a first bridge output of the wheatstone bridge is connected to a first input of a differential amplifier 46 via a temperature compensation circuit 45; a second bridge output of the wheatstone bridge is connected to a second input of the differential amplifier 46; the output end of the differential amplifier 46 is connected with the signal input end of the processor 41 through the analog-to-digital converter 44; wherein the wheatstone bridge is formed by connecting piezoresistive strips 221.
Specifically, the processor 41 may be a single chip, an MCU chip, or the like, and the temperature compensation circuit 45 may be a parallel circuit of a thermistor and a non-thermistor with a small temperature coefficient (smaller than a set threshold), which is not limited herein.
Because the signal processing circuit 4 uses fewer elements and the number of switches is reduced by using the one-in-one-out controllable switch 42, the signal processing circuit 4 can be manufactured into a small-sized PCB, so that the metal plate 1, the piezoresistive sensing module 2, the alternating magnetic field generating device 3 and the signal processing circuit 4 can be tightly packaged to form an isolated piezoresistive sensing system with a pressure self-testing function.
The working principle of the embodiment is as follows:
in the embodiment, a metal plate 1 is additionally arranged on a sensitive film of a piezoresistive sensing module 2 through an MEMS (micro-electromechanical systems) processing technology. When the whole piezoresistive sensing module 2 is in an alternating magnetic field, an eddy current electromagnetic force which is alternating up and down is generated on the metal plate 1 due to an eddy current effect, a sensitive film of the piezoresistive sensing module 2 is deformed due to the eddy current electromagnetic force, so that the resistance value of the piezoresistor is changed, the piezoresistive sensing module 2 outputs an alternating time harmonic voltage signal representing the resistance variation through a Wheatstone bridge, the alternating time harmonic voltage signal is transmitted to the processor 41 after temperature compensation and differential amplification, and finally the resistance variation, which is output by the processor 41 and represents the deformation of the film of the piezoresistive sensing module 2 due to the eddy current electromagnetic force, so that the pressure self-test of the absolute pressure type piezoresistive sensing system is realized.
Fig. 5 is a flowchart of a self-testing method of an absolute pressure type piezoresistive sensing system according to an embodiment of the present invention, where the method is applied to any one of the absolute pressure type piezoresistive sensing systems, and specifically includes:
and 11, supplying power to the metal plate by using alternating current with a set frequency so as to enable the metal plate to generate eddy current electromagnetic force towards the piezoresistive sensing module.
And step 12, acquiring a pressure sensing signal output by the piezoresistive sensing module under the action of the eddy current electromagnetic force.
The pressure sensing signal is a voltage value representing the resistance variation of the piezoresistive sensing module.
In this embodiment, the solenoid coil is energized with an alternating current of a predetermined frequency to generate an alternating magnetic field, and the metal plate is used as a self-test structure to generate an eddy electromagnetic force under the action of the alternating magnetic field, so as to drive the thin film layer of the piezoresistive sensing module to deform, thereby changing the resistance value of the piezoresistive strip, wherein the variation of the resistance value is directly related to the deformation of the thin film layer.
And step 13, obtaining the dynamic characteristics of the piezoresistive sensing module according to the pressure sensing signals.
In order to realize built-in self test of the absolute pressure type piezoresistive sensing system, the test voltage excitation signal on the chip is used as input in the embodiment, so that the sensitive film of the piezoresistive sensing module can also deform under the condition of not receiving external applied force. The controllable switch is used for controlling the working mode of the absolute pressure type piezoresistive sensing system and accessing a power supply voltage signal required by the absolute pressure type piezoresistive sensing system during self-testing. In the self-test mode, a control signal of the controllable switch is generated by the processor, and the control signal provides alternating power supply voltage for the solenoid coil through the I/O interface and the digital-to-analog converter, so that the solenoid coil generates an alternating magnetic field, and the metal plate can generate an eddy current electromagnetic force which is alternating up and down in the magnetic field. And then, corresponding temperature compensation is carried out on the output voltage of the piezoresistive sensing module by combining a temperature compensation circuit, and when alternating currents with different frequencies or different magnitudes are conducted in the solenoid coil below the piezoresistive sensing module, the electromagnetic force generated in the metal plate structure on the sensitive film is different in magnitude. The piezoresistive sensing module expresses the deformation condition of the sensitive film by outputting the change value of the piezoresistor, so that the test of the absolute pressure type piezoresistive sensor self-test circuit on the process defects and various dynamic characteristics of the piezoresistive sensing module is completed.
The embodiment realizes the diagnosis and test of the process defects and various dynamic characteristics of the MEMS piezoresistive sensor by utilizing on-chip electric excitation without an additional standard test signal source. The impact of the external environment on the output signal is avoided, the use cost of piezoresistive sensor testing equipment is saved, and the piezoresistive sensor testing equipment has the characteristics of simple structure, convenience in operation, low cost and the like. Meanwhile, after the sensing system is put into use for a period of time, self-testing on various dynamic characteristics of the sensing system can still be realized, so that the accuracy of data acquired by the piezoresistive sensing system is ensured.
The technical scheme provided by the embodiment of the invention at least has the following technical effects or advantages:
in the embodiment of the invention, a metal plate is arranged on one side of the piezoresistive sensing module, an alternating magnetic field generating device is arranged on the other side of the piezoresistive sensing module, because the alternating magnetic field generating device can form the alternating magnetic field near the piezoresistive sensing module at one side close to the glass layer, because of the eddy current effect, the metal plate can generate eddy current electromagnetic force with the direction changing alternately in the alternating magnetic field, so that the absolute pressure type piezoresistive sensing system can carry out pressure self-test according to the eddy current electromagnetic force, the processes of building off-chip test equipment and repeatedly disassembling and testing are omitted, the detection efficiency of the absolute pressure type piezoresistive sensing system is improved, the sensor can realize the self-test of the function without depending on the traditional test equipment, and simultaneously after the sensor is put into use for a period of time, on the basis of not needing to dismantle the sensor, still can realize the test to sensor performance.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. An absolute pressure piezoresistive sensing system, comprising: the piezoresistive sensing module comprises a metal plate, a piezoresistive sensing module, an alternating magnetic field generating device and a signal processing circuit;
the piezoresistive sensing module comprises: the protective layer, the thin film layer, the silicon substrate layer and the glass layer are stacked; a cavity structure is arranged in the silicon substrate layer; one side of the thin film layer, which is close to the protective layer, is provided with a piezoresistive strip; a metal electrode is arranged on one side of the protective layer, which is far away from the thin film layer; the metal electrode is electrically connected with the piezoresistive strip;
the metal plate is arranged on one side of the protective layer, which is far away from the thin film layer;
the alternating magnetic field generating device is arranged on one side of the glass layer far away from the silicon substrate layer;
the signal input end of the signal processing circuit is connected with the signal output end of the piezoresistive sensing module; and the signal processing circuit is respectively connected with the alternating magnetic field generating device and the piezoresistive sensing module in a power supply manner.
2. The absolute pressure piezoresistive sensing system according to claim 1, wherein said metal plate is an aluminum metal disk, a gold metal disk or a silver metal disk.
3. The absolute pressure piezoresistive sensing system according to claim 2, wherein the metal plate is an equal thickness disk-like structure.
4. The absolute pressure piezoresistive sensing system according to claim 1, wherein the protection layer is a silicon nitride layer or a silicon dioxide layer.
5. The absolute pressure piezoresistive sensing system according to claim 1, wherein the alternating magnetic field generating device comprises a fixed frame and a solenoid; the solenoid coil is arranged in the fixing frame.
6. The absolute pressure piezoresistive sensing system according to claim 5, wherein said solenoid is located centrally on a side of said glass layer remote from said silicon substrate layer.
7. The absolute pressure piezoresistive sensing system according to claim 6, wherein said solenoid is a copper wire solenoid.
8. The absolute pressure piezoresistive sensing system according to claim 5, wherein the signal processing circuitry comprises a processor, a controllable switch, a digital-to-analog converter, an analog-to-digital converter, a temperature compensation circuit, and a differential amplifier;
the power supply output end of the processor is connected with the first switch input end of the controllable switch through the digital-to-analog converter; the control end of the processor is connected with the switch control end of the controllable switch;
the first switch output end of the controllable switch is grounded through the solenoid coil;
the second switch output end of the controllable switch is connected with the first bridge input end of the Wheatstone bridge; a second bridge input terminal of the Wheatstone bridge is grounded; a first bridge output end of the Wheatstone bridge is connected with a first input end of the differential amplifier through the temperature compensation circuit; a second bridge output end of the Wheatstone bridge is connected with a second input end of the differential amplifier; the output end of the differential amplifier is connected with the signal input end of the processor through the analog-to-digital converter; wherein the Wheatstone bridge is formed by connecting the piezoresistive strips.
9. The absolute pressure piezoresistive sensing system according to claim 8, wherein the temperature compensation circuit comprises a thermistor and a non-thermistor with a temperature coefficient less than a set threshold; the thermistor and the non-thermistor are connected in parallel.
10. A method for self-testing of an absolute pressure piezoresistive sensing system according to any of claims 1 to 9, the method comprising:
supplying power to the metal plate by using alternating current with a set frequency so as to enable the metal plate to generate eddy current electromagnetic force towards the piezoresistive sensing module;
acquiring a pressure sensing signal output by the piezoresistive sensing module under the action of the eddy current electromagnetic force; the pressure sensing signal is a voltage value representing the resistance variation of the piezoresistive sensing module;
and obtaining the dynamic characteristic of the piezoresistive sensing module according to the pressure sensing signal.
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