Resonant pressure sensor open-loop test circuit capable of improving signal-to-noise ratio

Abstract

The utility model discloses a resonant pressure sensor open-loop test circuit capable of improving signal-to-noise ratio, which comprises a movable pole plate, the upper end of the movable pole plate is connected with a first driving pole plate, a first detection pole plate and a second detection pole plate, the first driving pole plate is connected between the first detection pole plate and the second detection pole plate, and the second driving pole plate is connected between the first detection pole plate and the second detection pole plate. The lower end of the movable polar plate is connected with a second driving polar plate, a third detection polar plate and a fourth detection polar plate, the second driving polar plate is connected between the third detection polar plate and the fourth detection polar plate, and a capacitor C1 is connected between the first detection polar plate and the movable polar plate. According to the resonant pressure sensor open-loop test circuit capable of improving the signal-to-noise ratio, an interface circuit with low cost and a simple structure is provided for open-loop test of a resonant capacitive sensor, co-frequency interference is avoided through specific connection and driving voltage selection, and the signal-to-noise ratio of the open-loop test is improved.

Description

Technical Field

[0001] The utility model relates to the field of pressure sensor signal processing, in particular to a resonant pressure sensor open-loop test circuit capable of improving the signal-to-noise ratio. Background Art

[0002] The resonant pressure sensor open-loop test circuit is a signal processing circuit used in resonant pressure sensors. Resonant pressure sensors are characterized by high precision, strong noise immunity, and high stability. Resonant pressure sensors have complex sensing structures and demanding process requirements. They also require an interface circuit to form a closed-loop circuit for pressure measurement. To determine the sensor's resonant frequency and quality factor, an open-loop test is generally required.

[0003] Among these sensors, resonant pressure sensors, which utilize electrostatic excitation and capacitive detection, offer advantages such as simple manufacturing and compact size. However, during resonance, the capacitor plates vibrate with a small amplitude, resulting in low sensitivity. Furthermore, because the drive signal contains an AC component and there is significant parasitic capacitance between the plates, this AC component of the drive signal is coupled to the detection terminal via the parasitic capacitance. This signal is significantly larger than the resonant signal and has the same frequency, generating co-channel interference. In open-loop testing, this co-channel interference is the primary source of reduced signal-to-noise ratio (SNR) in the output signal.

[0004] Co-frequency interference is usually eliminated through corresponding interface circuits. For example, by applying a carrier signal to the movable plate, cooperating with relevant demodulation circuits and low-pass and high-pass filters, the resonant signal and the interference signal are separated. However, the circuit is relatively complex and costly, and the circuit is composed of multiple stages. Each stage will introduce excess noise, thereby reducing the effect. To this end, we propose an open-loop test circuit for a resonant pressure sensor that can improve the signal-to-noise ratio. Utility Model Content

[0005] Technical problem solved: In response to the shortcomings of the existing technology, the utility model provides an open-loop test circuit for a resonant pressure sensor that can improve the signal-to-noise ratio, and provides a low-cost, simple-structure interface circuit for the open-loop test of a resonant capacitance sensor. Through specific connection methods and drive voltage selection, it avoids co-frequency interference, improves the signal-to-noise ratio of the open-loop test, and can effectively solve the problems in the background technology.

[0006] Technical solution: In order to achieve the above-mentioned purpose, the technical solution adopted by the utility model is: a resonant pressure sensor open-loop test circuit that can improve the signal-to-noise ratio, including a movable electrode plate, the upper end position of the movable electrode plate is connected to a first driving electrode plate, a first detection electrode plate and a second detection electrode plate, the first driving electrode plate is connected between the first detection electrode plate and the second detection electrode plate, the lower end position of the movable electrode plate is connected to the second driving electrode plate, a third detection electrode plate and a fourth detection electrode plate, and the second driving electrode plate is connected between the third detection electrode plate and the fourth detection electrode plate.

[0007] Preferably, a capacitor C1 is connected between the first detection plate and the movable plate, a capacitor C3 is connected between the second detection plate and the movable plate, a capacitor C2 is connected between the first drive plate and the movable plate, and a parasitic capacitor C is connected between the first drive plate and the first detection plate. p1 A parasitic capacitor C is connected between the first driving plate and the second detecting plate. p2 .

[0008] Preferably, a capacitor C4 is connected between the third detection plate and the movable plate, a capacitor C5 is connected between the fourth detection plate and the movable plate, a capacitor C6 is connected between the second drive plate and the movable plate, and a parasitic capacitor C is connected between the second drive plate and the third detection plate. p3 A parasitic capacitor C is connected between the second driving plate and the fourth detecting plate. p4 .

[0009] Preferably, the parasitic capacitance C p1 Connected with drive circuit C s1 , the parasitic capacitance C p2 Connected with drive circuit C s2 , the parasitic capacitance C p1 and parasitic capacitance C p2 They are all connected to the feedback capacitor C, the resonant capacitor C' and the circuit output V0.

[0010] Preferably, the parasitic capacitance C p1 , parasitic capacitance C p2 , drive circuit C s1 , drive circuit C s2 , feedback capacitor C, resonant capacitor C' and circuit output V0 constitute the interface circuit.

[0011] Preferably, the interface circuit is isolated from direct current through a coupling capacitor at the output end, so that the output signal is proportional to the capacitance change and there is no co-frequency interference signal.

[0012] Beneficial effects: Compared with the prior art, the utility model provides an open-loop test circuit for a resonant pressure sensor that can improve the signal-to-noise ratio, and has the following beneficial effects: This open-loop test circuit for a resonant pressure sensor that can improve the signal-to-noise ratio provides a low-cost, simple-structure interface circuit for the open-loop test of a resonant capacitance sensor. Through a specific connection method and drive voltage selection, co-frequency interference is avoided, and the signal-to-noise ratio of the open-loop test is improved. The entire open-loop test circuit for the resonant pressure sensor has a simple structure, is easy to operate, and has a better effect than the traditional method. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The utility model is a schematic diagram of the overall structure of an open-loop test circuit of a resonant pressure sensor capable of improving the signal-to-noise ratio.

[0014] Figure 2 The utility model is a schematic diagram of an interface circuit in an open-loop test circuit of a resonant pressure sensor capable of improving the signal-to-noise ratio.

[0015] In the figure: 1, first driving plate; 2, first detection plate; 3, second detection plate; 4, movable plate; 5, third detection plate; 6, fourth detection plate; 7, second driving plate. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but those skilled in the art will understand that the embodiments described below are part of the embodiments of the present invention, rather than all of the embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0017] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating positions or relationships, are based on the positions or relationships shown in the accompanying drawings and are intended solely to facilitate the description of this utility model and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0018] In the description of this utility model, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0019] like Figure 1 、 2 As shown, a resonant pressure sensor open-loop test circuit capable of improving the signal-to-noise ratio includes a movable electrode 4, the upper end of the movable electrode 4 is connected to a first driving electrode 1, a first detection electrode 2, and a second detection electrode 3, the first driving electrode 1 is connected between the first detection electrode 2 and the second detection electrode 3, the lower end of the movable electrode 4 is connected to a second driving electrode 7, a third detection electrode 5, and a fourth detection electrode 6, the second driving electrode 7 is connected between the third detection electrode 5 and the fourth detection electrode 6, providing a low-cost, simple-structure interface circuit for the open-loop test of the resonant capacitive sensor, avoiding co-frequency interference through specific connection methods and drive voltage selection, and improving the signal-to-noise ratio of the open-loop test.

[0020] Furthermore, a capacitor C1 is connected between the first detection plate 2 and the movable plate 4, a capacitor C3 is connected between the second detection plate 3 and the movable plate 4, a capacitor C2 is connected between the first drive plate 1 and the movable plate 4, and a parasitic capacitor C is connected between the first drive plate 1 and the first detection plate 2. p1 A parasitic capacitor C is connected between the first driving plate 1 and the second detecting plate 3. p2 .

[0021] Furthermore, a capacitor C4 is connected between the third detection plate 5 and the movable plate 4, a capacitor C5 is connected between the fourth detection plate 6 and the movable plate 4, a capacitor C6 is connected between the second drive plate 7 and the movable plate 4, and a parasitic capacitor C is connected between the second drive plate 7 and the third detection plate 5. p3 A parasitic capacitor C is connected between the second driving electrode plate 7 and the fourth detecting electrode plate 6. p4 .

[0022] Furthermore, the parasitic capacitance C p1 Connected with drive circuit C s1 , parasitic capacitance C p2 Connected with drive circuit C s2 , parasitic capacitance C p1 and parasitic capacitance C p2 They are all connected to the feedback capacitor C, the resonant capacitor C' and the circuit output V0.

[0023] Furthermore, the parasitic capacitance C p1 , parasitic capacitance C p2 , drive circuit C s1 , drive circuit C s2 , feedback capacitor C, resonant capacitor C' and circuit output V0 constitute the interface circuit.

[0024] Furthermore, the interface circuit isolates direct current through a coupling capacitor at the output end, so that the output signal is proportional to the capacitance change and there is no co-frequency interference signal.

[0025] Working principle: The utility model includes a first driving plate 1, a first detection plate 2, a second detection plate 3, a movable plate 4, a third detection plate 5, a fourth detection plate 6, and a second driving plate 7, which provides a low-cost, simple-structure interface circuit for open-loop testing of resonant capacitive sensors. Through specific connection methods and drive voltage selection, co-frequency interference is avoided and the signal-to-noise ratio of the open-loop test is improved.

[0026] Figure 1 The following is a schematic diagram of the sensor structure. The same-frequency interference can be eliminated by the following method:

[0027] 1. Apply V to driving electrode 1 and driving electrode 2 respectively. DC +V m sinWt, -V DC -V m sinWt,V DC is the driving DC voltage, V m sinWt is the driving AC voltage. DC ×V m The value can meet the resonant vibration amplitude requirement.

[0028] 2. Ground potential of movable plate;

[0029] 3. Connect the detection electrode to DC voltage n1 is the number of comb tooth pairs of a single driving electrode, and n2 is the sum of the numbers of comb tooth pairs of two adjacent detection electrodes.

[0030] At this time, the attraction force F1 exerted by the driving electrode pair 1 on the movable plate is:

[0031] F1=k·n1(V DC +V m sinWt) 2

[0032] =k·n1(V DC 2 +(V m sinWt) 2 +2V DC ·V msinWt)

[0033] The attraction F2 of the detection plate 1 and the detection plate 2 to the movable plate is:

[0034]

[0035] Then the net force on the upper part of the movable plate is F1-F2:

[0036] F1-F2=k·n1((V m sinWt) 2 +2V DC ·V m sinWt)

[0037] Similarly, the attraction force F3 exerted by the driving electrode 2 on the movable plate is:

[0038] F3=k·n1(-V DC -V m sinWt) 2

[0039] =k·n1(V DC 2 +(V m sinWt) 2 +2V DC ·V m sinWt)

[0040] The net force on the lower part of the movable plate is k·n1((V m sinWt) 2 +2V DC ·V m sinWt), the forces on the upper and lower parts of the movable plate are equal and in opposite directions, satisfying the vibration condition.

[0041] Figure 2 For the interface circuit, C s1 、C s2 、C p1 、C p2 and C' are respectively the driving capacitance of the capacitance between the driving electrode plate 1 and the movable electrode plate, the driving capacitance of the capacitance between the driving electrode plate 2 and the movable electrode plate, the sum of the parasitic capacitance between the driving electrode plate 1 and the detection electrodes 1 and 2, the sum of the parasitic capacitance between the driving electrode plate 2 and the detection electrodes 3 and 4, and the sum of the resonant capacitance between all the detection electrodes and the movable electrode plate. Figure 2 China needs to ensure

[0042] W0 is the theoretical resonant frequency of the sensor. s1 =C s2 =C s , C p1=C p2 =C p . C · =C0+ΔC, where C0 is the static capacitance and ΔC is the capacitance change caused by the sensor resonating.

[0043] Figure 2 Interface circuit output V O for:

[0044]

[0045] By using a coupling capacitor at the output end to isolate DC, the output signal is proportional to the change in capacitance and there is no co-frequency interference signal.

[0046] It should be noted that, in this article, relational terms such as first and second (number one, number two), etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also includes elements that are inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including a..." do not exclude the presence of other identical elements in the process, method, article or device that includes the elements.

[0047] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and improvements shall fall within the scope of the present invention as claimed.

Claims

1. A resonant pressure sensor open-loop test circuit capable of improving the signal-to-noise ratio, comprising a movable plate (4), characterized in that: The upper end of the movable electrode plate (4) is connected to a first driving electrode plate (1), a first detection electrode plate (2) and a second detection electrode plate (3); the first driving electrode plate (1) is connected between the first detection electrode plate (2) and the second detection electrode plate (3); the lower end of the movable electrode plate (4) is connected to a second driving electrode plate (7), a third detection electrode plate (5) and a fourth detection electrode plate (6); the second driving electrode plate (7) is connected between the third detection electrode plate (5) and the fourth detection electrode plate (6).

2. The resonant pressure sensor open-loop test circuit capable of improving the signal-to-noise ratio according to claim 1, characterized in that: A capacitor C1 is connected between the first detection plate (2) and the movable plate (4), a capacitor C3 is connected between the second detection plate (3) and the movable plate (4), a capacitor C2 is connected between the first drive plate (1) and the movable plate (4), and a parasitic capacitor C is connected between the first drive plate (1) and the first detection plate (2). p1 A parasitic capacitor C is connected between the first driving plate (1) and the second detecting plate (3). p2 .

3. The resonant pressure sensor open-loop test circuit capable of improving the signal-to-noise ratio according to claim 1, characterized in that: A capacitor C4 is connected between the third detection plate (5) and the movable plate (4), a capacitor C5 is connected between the fourth detection plate (6) and the movable plate (4), a capacitor C6 is connected between the second drive plate (7) and the movable plate (4), and a parasitic capacitor C is connected between the second drive plate (7) and the third detection plate (5). p3 A parasitic capacitor C is connected between the second driving plate (7) and the fourth detecting plate (6). p4 .

4. The resonant pressure sensor open-loop test circuit capable of improving the signal-to-noise ratio according to claim 2, characterized in that: The parasitic capacitance C p1 Connected with drive circuit C s1 , the parasitic capacitance C p2 Connected with drive circuit C s2 , the parasitic capacitance C p1 and parasitic capacitance C p2 They are all connected to the feedback capacitor C, the resonant capacitor C' and the circuit output V0.

5. The resonant pressure sensor open-loop test circuit capable of improving the signal-to-noise ratio according to claim 4, characterized in that: The parasitic capacitance C p1 , parasitic capacitance C p2 , drive circuit C s1 , drive circuit C s2 , feedback capacitor C, resonant capacitor C' and circuit output V0 constitute the interface circuit.

6. The resonant pressure sensor open-loop test circuit capable of improving the signal-to-noise ratio according to claim 5, characterized in that: The interface circuit is isolated from direct current through a coupling capacitor at the output end, so that the output signal is proportional to the capacitance change and there is no co-frequency interference signal.

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