CN117928811A - Dual-mode resonant pressure sensor - Google Patents

Abstract

The present invention provides a dual-mode resonant pressure sensor, which enables the same MEMS sensitive chip to achieve full-range pressure measurement from medium and low vacuum to atmospheric pressure by simply switching the working mode. In the pressure section greater than the low vacuum, the measurement is achieved by a resonant pressure sensor composed of multiple (2 or more) single resonators or a single resonator with a thermal sensitive component. The sensor will have high-precision output characteristics in this part and can work stably in a wide temperature range. In the medium and low vacuum pressure section, multiple single resonators (no less than 2) are coupled together, and the coupling stiffness is adjusted to make the coupling system work in a weak coupling state. At this time, the sensor produces a modal localization phenomenon, thereby obtaining high sensitivity characteristics and realizing high-sensitivity measurement of low vacuum pressure.

Description

A dual-mode resonant pressure sensor

Technical Field

The invention belongs to the field of MEMS pressure sensor design, and in particular relates to a dual-mode resonant pressure sensor.

Background technique

The traditional resonant pressure sensor is only suitable for pressure measurement above the low vacuum range (greater than 0.5kPa) due to its strain mechanism. Although it has ultra-high precision, it cannot measure the pressure in the low and medium vacuum range. The existing full-range pressure sensors, that is, measuring the pressure from atmospheric pressure to medium and low vacuum or high vacuum range, are generally based on the principle of thermal viscous damping or combined with thin film and ionization vacuum gauges to form a composite vacuum gauge to achieve this goal. The accuracy is usually low (no better than 10% reading accuracy), and the composite vacuum gauge is complex. At present, there is little research on high-sensitivity low-pressure pressure measurement and high-precision normal pressure measurement based on a sensor chip.

Xiao Dingbang et al. first proposed to measure atmospheric pressure to high vacuum pressure through a sensor chip in the cited patent 202010525596 "A full-range vacuum gauge and its test method". It uses the multi-order modes of the resonator and combines multiple resonator excitation-response relationships to measure different pressure levels. In the low and medium vacuum range, it simply relies on the damping-related quantity-quality factor to characterize the ambient pressure. Many studies have shown that this working mode is complex to test, has low linearity and low accuracy, and can only be measured through open-loop excitation, which is not conducive to the miniaturization and stable operation of the device.

Existing full-scale vacuum pressure measurement solutions mostly use two separate sensors for measurement and display through instrument integration, which increases the complexity of the system and is not conducive to system integration. At present, the measurement of low vacuum pressure range mostly uses piezoresistive or damping sensor components, so the accuracy is low and the sensitivity is limited. In addition, the existing solutions can only work around 25°C, and there is no research or invention that can adapt to lower temperatures (below 5°C) and higher temperatures (above 50°C), which limits the application of sensors to a certain extent.

Summary of the invention

The present invention utilizes the same MEMS sensitive chip to achieve measurement of medium and low vacuum to atmospheric pressure by simply switching the working mode. In the pressure section above medium and low vacuum, it is realized by a resonant pressure sensor composed of multiple (2 or more) single resonators or a single resonator with a thermal sensitive component. The sensor will have high-precision output characteristics in this part and can work stably in the above-mentioned wide temperature range. In the medium and low vacuum pressure section, multiple resonators (no less than 2) are coupled together, and the coupling stiffness is adjusted to make the coupling system work in a weak coupling state. At this time, the sensor produces a modal localization phenomenon. Studies have shown that high sensitivity (or high resolution) characteristics can be obtained by this, and high-sensitivity measurement of low vacuum pressure can be achieved.

The present invention provides a dual-mode resonant pressure sensor, the dual-mode resonant pressure sensor comprises a resonator group, the resonator group comprises at least two single resonators, wherein:

In the pressure range above low vacuum, that is, P≥P ₀ , the monomer resonators of the resonator group are not coupled, and the monomer resonators will be sensitive to pressure respectively, and each will generate a resonant frequency output. By simultaneously solving the resonant frequency of some monomer resonators or solving the frequency of one of the monomer resonators and the output value of the heat-sensitive component, the pressure value to be measured at this temperature is obtained;

In the low to medium vacuum range, ie, P<P ₀ , the monomer resonators of the resonator group are weakly coupled, causing the resonator group to produce modal localization. At this time, the measured value of the pressure to be measured at this temperature is obtained by solving the amplitude information of each monomer resonator and the output value of the thermal sensitive component.

Furthermore, the resonator group is a two-degree-of-freedom coupled resonator based on electrostatic coupling achieved by electrostatic force; two single resonators are fixed on the pressure diaphragm of the pressure sensor through anchor points, and their respective excitation and vibration pickup are achieved through electrodes during operation. The coupling structure based on electrostatic force achieves a soft connection with the two single resonators through two coupling electrodes, and the sensitivity of the sensor is adjusted by adjusting the strength of the electrostatic force and the number and position of the coupling structure anchor points. At this time, the structure and size of the two single resonators are exactly the same.

Further, in the low to medium vacuum range, that is, P<P ₀ , when the resonator group works in a weak coupling state, the measured value P of the pressure to be measured at temperature T is obtained by using the amplitude information R ₁ and R ₂ of at least two monomer resonators and the output value V of the thermosensitive component:

P(T)＝ _g2 ( _g1 ( _R1 , _R2 ),V)

Wherein, g ₁ (·) represents the preprocessing function of the amplitude information R ₁ and R ₂ , g ₂ (·) represents the functional relationship between the pressure P to be measured and the temperature T with the amplitude related information g ₁ (R ₁ , R ₂ ) and V as independent variables;

In the pressure range above low vacuum (P≥P ₀ ), by simultaneously solving the resonant frequencies f ₁ and f ₂ of at least two monomer resonators or solving the frequency _{fi of} one of the monomer resonators and the output value V of the heat-sensitive component, the pressure value P to be measured at temperature T can be obtained as:

P(T) = _h1 ( _f1 , _f2 ) or P(T) = _h2 ( _f1 , V)

Wherein, h ₁ (·) and h ₂ (·) represent the functional relationship between the pressure P to be measured and the temperature T with the frequency fi and V as independent variables.

The present invention has the following beneficial technical effects:

The sensors in the low and medium vacuum pressure section work in weak coupling mode and have high sensitivity. The sensors in the pressure section above low vacuum work in traditional resonant mode and have high precision. They can work in the range of lower temperature (less than 5°C) to higher temperature (greater than 50°C). Through a sensitive chip, a wide range of pressure measurement from low and medium vacuum pressure to atmospheric pressure can be achieved, and the sensors in the low and medium vacuum pressure section have ultra-high sensitivity. The sensors in the pressure section above low vacuum can measure pressure with high precision, and their performance is comparable to that of traditional resonant pressure sensors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a cross-sectional view of a pressure sensor chip;

FIG2 is a two-degree-of-freedom coupled resonator based on mechanical coupling realized by a mechanical structure;

FIG3 is a two-degree-of-freedom coupled resonator based on electrostatic coupling achieved by electrostatic force;

FIG4 is a flowchart of a solution for calculating temperature based on a single resonator and a temperature measuring component when the sensor P ≥ P ₀ ;

FIG5 is a flowchart of a solution for calculating temperature based on multiple (at least 2) single resonators when sensor P≥P ₀ .

Detailed ways

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

As shown in FIG1 , a cross-sectional view of a dual-mode resonant pressure sensor chip used in the example is shown. The dual-mode resonant pressure sensor chip has a total of four layers: a cover layer 101, a resonator layer 102, a substrate layer 103, and an isolation layer 104. Several electrode lead holes 101.1 are distributed on the cover layer 101, which are used to lead out the signal of the resonator group 102.1. The cover layer 101 has a thermal sensitive component 101.2, which is used to measure the ambient temperature to assist in solving the pressure measurement value at any temperature, so as to realize the wide temperature range operation of the sensor. The resonator group 102.1 is located in the resonator layer 102, and is connected to the pressure diaphragm 103.1 of the substrate layer 103 via an anchor point. The resonator group 102.1 includes at least two single resonators (such as a double-end fixed-beam resonator), and the sensitivity of each single resonator to pressure must be ensured to be different. There is a vent 104.1 on the isolation layer 104 for introducing the pressure to be measured into the pressure diaphragm 103.1.

FIG2 is a two-degree-of-freedom coupled resonator based on mechanical coupling realized by a mechanical structure, which is a specific implementation of the resonator group 102.1 in FIG1 . The coupled resonator is composed of two monomer resonators 201.1 and 201.2 of the same structure and a coupling structure 205. The monomer resonators 201.1 and 201.2 are fixed on the pressure diaphragm 103.1 through anchor points 208, and each monomer resonator 201.1 and 201.2 has tuning electrodes 202 and 206, respectively. When working, the electrodes 203 and 207 are used to realize respective excitation and vibration pickup. When the resonant frequencies of the two monomer resonators 201.1 and 201.2 are consistent, the two will be coupled through the coupling structure 205. In order to make the sensor work in a weak coupling mode within a set pressure range, it is necessary to adjust the position or number of the fixed anchor points 205.1 so that the bending stiffness of the coupling structure 205 is much smaller than the stiffness of the monomer resonator 201.1 and the monomer resonator 201.2. When the frequencies of the two are inconsistent, they will no longer work in a coupled mode, but will be equivalent to two separate resonators. Here, the lengths or widths of resonators 201.1 and 201.2 are slightly different, so that the resonant frequencies of the two at pressure P ₀ have a frequency difference of not less than 50 Hz.

In the low to medium vacuum range (P<P ₀ ), if the resonance frequencies of the two monomer resonators 201.1 and 201.2 are inconsistent and cannot be coupled, the electrostatic force can be applied by tuning electrodes 202 and 206 to achieve weak coupling between the two. At this time, the sensitivity of the sensor is inversely proportional to the coupling stiffness of the coupling structure 205. By reducing the coupling stiffness of the coupling structure 205, that is, weak coupling, the sensor will have the ability to sense pressure with high sensitivity. At this time, the amplitude information R ₁ and R ₂ of the resonators 201.1 and 201.2 and the output value V of the heat-sensitive component 101.2 are solved by the following formula to obtain the measured value P of the pressure to be measured at temperature T:

P(T)＝ _g2 ( _g1 ( _R1 , _R2 ),V)

Wherein, g ₁ (·) represents a preprocessing function of the amplitude information R ₁ and R ₂ , and g ₂ (·) represents a functional relationship between the pressure P to be measured and the temperature T with the amplitude-related information g ₁ (R ₁ , R ₂ ) and V as independent variables, and its specific form depends on the specific sensor.

In the pressure range above low vacuum (P≥P ₀ ), the voltage of the suspended harmonic electrodes 202 and 206 is such that the two monomer resonators 201.1 and 201.2 will never be coupled within the measuring range due to the inconsistency of the fundamental frequency and sensitivity. The monomer resonators will respectively generate frequency outputs of the sensitive pressures, which is consistent with the working state of the traditional resonant pressure sensor. By simultaneously solving the resonant frequencies f ₁ and f ₂ of the two monomer resonators or solving the frequency _fi of one of the monomer resonators and the output value V of the heat-sensitive component 101.2, the pressure value P to be measured at the temperature T can be obtained as:

P(T)＝h ₁ (f ₁ ,f ₂ )

or

P(T)＝ _h2 ( _fi ,V)

Wherein, h ₁ (·) and h ₂ (·) represent the functional relationship between the pressure P to be measured and the temperature T with the frequency fi and V as independent variables. The specific form depends on the specific sensor, and thus a high-precision output of the pressure value in a wide temperature range (the lower limit of the temperature is lower than 5°C and the upper limit is higher than 50°C) can be achieved.

FIG3 is a two-degree-of-freedom coupled resonator based on electrostatic coupling realized by electrostatic force. This is an equivalent solution of FIG2 , which is another specific implementation of the resonator 102.1 in FIG1 . The monomer resonators 301.1 and 301.2 are fixed on the pressure diaphragm 103.1 through the anchor point 308, and the electrodes 303 and 307 are used to realize their respective excitation and vibration pickup during operation. The coupling structure 305 is softly connected to the monomer resonators 301.1 and 301.2 through two coupling electrodes 305.2. At this time, the structure and size of the monomer resonators 301.1 and 301.2 are exactly the same. When measuring low and medium vacuum pressure (P<P ₀ ), a voltage is applied to the coupling electrode 305.2 so that the two monomer resonators are softly connected to the coupling structure 305 through electrostatic force. The strength of the soft connection can be controlled by this voltage or the position and number of the anchor points 305.1. Then, by adjusting the voltages of the tuning electrodes 302 and 306, the weak coupling of the two monomer resonators can be achieved. The electrode 304 is a suspended electrode, which is only used to form a symmetrical structure with the coupling electrode 305.2 and works in a high sensitivity mode induced by modal localization. When measuring the pressure range above low vacuum (P≥P ₀ ), the voltage of the coupling electrode 305.2 is adjusted so that the potential difference between the coupling electrode 305.2 and the two monomer resonators is zero. At this time, the two monomer resonators will work in the traditional resonant pressure sensor mode.

FIG4 is a flowchart of a solution for calculating temperature based on a single resonator and a temperature measuring component when the sensor P≥P _0. After startup, the sensor works in a conventional resonant pressure sensor state and measures the temperature through the temperature measuring component to generate an output V. If the pressure value P≥P ₀ , the sensor continues to work in a conventional resonant sensitive mode and outputs a pressure value P; if the pressure value P<P ₀ , the voltage of the tuning electrode 202 or 206 and the tuning electrode 302 or 306 in FIG2 and FIG3 is automatically adjusted to make the sensor work in a weak coupling resonant mode and calculate the pressure P to be measured at the temperature T based on the amplitude information R ₁ , R ₂ and the temperature information V and output the pressure value P. This reciprocating cycle realizes the pressure measurement of the sensor within the full range of pressure.

FIG5 is a flowchart of the solution for calculating the temperature based on multiple (at least 2) single resonators when the sensor _P≥P0 . After the sensor is turned on, it works in the traditional resonant pressure sensor state. If the pressure value _P≥P0 , the sensor continues to work in the traditional resonant sensitive mode, and calculates the ambient temperature T and the pressure P to be measured through the frequency information fusion of multiple single resonators and outputs the pressure value P; if the pressure value P< _P0 , the voltage of the tuning electrode 202 or 206 and the tuning electrode 302 or 306 in FIG2 and FIG3 is automatically adjusted to make the sensor work in the weak coupling resonance mode and calculate the pressure P to be measured at the temperature T based on the amplitude information _R1 , _R2 and the temperature information V and output the pressure value P. This reciprocating cycle realizes the pressure measurement of the sensor within the full range of pressure.

It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims (3)

1. A dual mode resonant pressure sensor, characterized in that the dual mode resonant pressure sensor comprises a resonator group comprising at least 2 individual resonators, wherein,

In the pressure section above the low vacuum, namely P is more than or equal to P ₀, the single resonators of the resonator group are not coupled, the single resonators are respectively sensitive to pressure and respectively generate resonant frequency output quantities, and the pressure value to be measured at the temperature is obtained by simultaneously calculating the resonant frequency of some single resonators or calculating the frequency of one single resonator and the output value of a thermosensitive component;

In the middle and low vacuum range, namely P < P ₀, the single resonators of the resonator group are weakly coupled, so that the resonator group generates a mode localization phenomenon, and at the moment, the amplitude information of each single resonator and the output value of the thermosensitive component are solved to obtain the measured value of the pressure to be measured at the temperature.

2. The sensor of claim 1, wherein the resonator group is a 2-degree-of-freedom coupled resonator based on electrostatic coupling achieved by electrostatic forces; the two single resonators are fixed on the pressure membrane of the pressure sensor through anchor points, respective excitation and vibration pickup are realized through electrodes during operation, the coupling structure based on electrostatic force is in soft connection with the two single resonators through the two coupling electrodes, and the sensitivity of the sensor is adjusted by adjusting the strength of the electrostatic force and the number and the position of the anchor points of the coupling structure, so that the structures and the sizes of the two single resonators are identical.

3. The sensor of claim 1, wherein the measured value P of the pressure to be measured at the temperature T is calculated by the at least two individual resonator amplitude information R ₁ and R ₂ and the thermosensitive member output value V in the medium and low vacuum range, i.e., P < P ₀, weak coupling:

P(T)＝g₂(g₁(R₁,R₂),V)

Wherein g ₁ (·) represents a preprocessing function for the amplitude information R ₁ and R ₂, g ₂ (·) is a functional relationship in which the amplitude related information g ₁(R₁,R₂) and V are independent variables to represent the pressure P and the temperature T to be measured;

In the pressure section (P is more than or equal to P ₀) above the low vacuum, the resonant frequencies f ₁ and f ₂ of at least two single resonators in the resonator group are solved simultaneously, or the frequency fi of one single resonator and the output value V of the thermosensitive component are solved, so that the pressure value P to be measured at the temperature T is obtained as follows:

P (T) =h ₁(f₁,f₂) or P (T) =h ₂(f_i, V

Wherein, h ₁ (·) and h ₂ (·) represent the function relationship of the measured pressure P and the temperature T with the frequencies f ₁、f₂ and V as independent variables.