CN110319971B - Measuring circuit for measuring pressure in bipolar capacitance type vacuum gauge - Google Patents
Measuring circuit for measuring pressure in bipolar capacitance type vacuum gauge Download PDFInfo
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- 230000006698 induction Effects 0.000 claims description 6
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- 239000012528 membrane Substances 0.000 abstract description 11
- 238000000034 method Methods 0.000 abstract description 4
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- 239000003990 capacitor Substances 0.000 description 6
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- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
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- 230000005669 field effect Effects 0.000 description 2
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- SLXKOJJOQWFEFD-UHFFFAOYSA-N 6-aminohexanoic acid Chemical compound NCCCCCC(O)=O SLXKOJJOQWFEFD-UHFFFAOYSA-N 0.000 description 1
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- 239000000956 alloy Substances 0.000 description 1
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- 238000009530 blood pressure measurement Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L21/00—Vacuum gauges
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Abstract
The invention relates to the field of vacuum gauge measurement, in particular to a measuring circuit for measuring the pressure in a bipolar capacitance type vacuum gauge, which comprises a shell, a diaphragm, a fixed substrate and a fixed electrode, wherein the fixed electrode is arranged on the shell; the diaphragm is fixedly arranged in the shell, the diaphragm divides the shell into two parts, one side is a vacuum cavity, and the other side is a detection cavity; the fixed substrate is fixedly arranged in the vacuum cavity, the fixed electrode is arranged on the fixed substrate, when the membrane is stressed to deform, the capacitance on the fixed electrode can change, and the pressure in the detection cavity can be obtained by detecting the change of the capacitance; the fixed electrode comprises an annular electrode and a circular electrode, the circular electrode is positioned in the annular electrode, and a space is reserved between the circular electrode and the annular electrode, so that the fixed electrode is divided into the annular electrode and the circular electrode, and the accuracy of the vacuum gauge can be effectively improved; the measuring circuit detects and processes the capacitance changes on the annular electrode and the circular electrode and then outputs a sine wave, and the pressure can be obtained by measuring the sine wave.
Description
Technical Field
The invention relates to the field of vacuum gauge metering, in particular to a measuring circuit for measuring pressure in a bipolar capacitance type vacuum gauge.
Background
The metal film vacuum gauge is a vacuum instrument which can be used as a working pair standard of low vacuum measurement (0.01-100 Pa), and is also a vacuum degree gauge with legal metering calibration test rules in China (calibration reference rules: Q/WHJ46-1998 standard type capacitance film vacuum gauge calibration rules). The metal capacitance film vacuum gauge is a vacuum gauge for absolute pressure and full pressure measurement, and is manufactured according to the principle that an elastic detection diaphragm generates strain under the action of pressure difference to cause capacitance change. The measurement of the vacuum gauge directly reflects the variation value of the vacuum pressure, is only related to the pressure and is irrelevant to the gas composition, so that the metal film vacuum gauge is a direct measurement type full-pressure vacuum gauge.
The difficulty of vacuum measurement is the small range and high accuracy. Under the existing process conditions, the single-capacitance metal film vacuum gauge can achieve the full range of 10Torr and the accuracy of 0.25% of the reading value, but the single-capacitance metal film vacuum gauge is difficult to achieve under the existing process of the single-capacitance metal film vacuum gauge when the range is continuously reduced, for example, the range is reduced to 0.1Torr and the accuracy value is still 0.25% of the reading value. Therefore, under the existing material and processing conditions, the problem of how to improve the precision needs to be solved.
Disclosure of Invention
First, the technical problem to be solved
The invention provides a bipolar capacitance type vacuum gauge and a corresponding measuring circuit thereof, and aims to solve the problem of low vacuum gauge precision in the prior art.
(II) technical scheme
In order to solve the problems, the bipolar capacitance type vacuum gauge comprises a shell, a diaphragm, a fixed substrate and a fixed electrode;
The diaphragm is fixedly arranged in the shell, the diaphragm divides the shell into two parts, one side is a vacuum cavity, and the other side is a detection cavity;
The fixed substrate is fixedly arranged in the vacuum cavity, and the fixed electrode is arranged on the fixed substrate;
The fixed electrode comprises a ring electrode and a circular electrode, wherein the circular electrode is positioned in the ring electrode, and a space is reserved between the circular electrode and the ring electrode.
Preferably, a detection hole for detecting pressure is formed in the detection cavity.
Preferably, the circular electrode and the ring electrode are disposed at a side of the fixed substrate facing the diaphragm, and an insulating layer is disposed at a space between the circular electrode and the ring electrode.
Preferably, when the diaphragm is deformed under the force, the distance change amount relative to the annular electrode is Δd Outer part , and the distance change amount relative to the circular electrode is Δd Inner part ;
The area ratio of the circular electrode to the annular electrode is equal to the ratio of Δd Inner part to Δd Outer part .
Preferably, the area ratio of the circular electrode to the annular electrode is 1:1 to 1.5:1.
Preferably, the diaphragm is a circular diaphragm, and the ratio of the outer diameter of the annular electrode to the diameter of the diaphragm is 0.7:1 to 1:1.
Preferably, the membrane is parallel to the fixed substrate when not stressed.
Preferably, a measuring circuit for measuring the pressure in the detection cavity in a bipolar capacitance type vacuum gauge comprises a common-substrate bridge detection circuit and an oscillating circuit;
the common-substrate bridge detection circuit is connected with the circular electrode and the annular electrode, and outputs induction voltage according to capacitance variation on the circular electrode and the annular electrode;
The common-substrate bridge detection circuit is connected with the oscillation circuit, the oscillation circuit outputs sine waves corresponding to the induction voltage according to the induction voltage, the amplitude of the sine waves corresponds to the magnitude of the induction voltage, and the frequency of the sine waves corresponds to the frequency of the induction voltage.
Preferably, the common-substrate bridge detection circuit comprises a first diode, a second diode, a third diode and a fourth diode, and the first diode, the second diode, the third diode and the fourth diode are sequentially connected end to form a closed loop;
The common-substrate bridge detection circuit comprises a first input end and a second input end, wherein the first input end is positioned at the joint of the first diode and the second diode, and the second input end is positioned at the joint of the third diode and the fourth diode;
The common-substrate bridge detection circuit further comprises a first output end and a second output end, wherein the first output end is positioned at the joint of the second diode and the third diode, and the second output end is positioned at the joint of the fourth diode and the first diode.
Preferably, the first input end is connected with the ring electrode through a wire, the second input end is connected with the circular electrode, and the first output end and the second output end are connected with the oscillating circuit.
(III) beneficial effects
According to the invention, the fixed electrode is added and is arranged as the circular electrode and the annular electrode, when the diaphragm is deformed, the zero capacitance of the circular electrode pole plate and the zero capacitance of the annular electrode pole plate are changed, and the corresponding external measuring circuit is matched, so that the change amount of the capacitance and the deformation of the measuring diaphragm are close to a linear relation, and compared with a single-electrode capacitance type film vacuum gauge, the precision of the vacuum gauge is improved by nearly twice, and the precision of the vacuum gauge with a small measuring range can be accurately improved.
Drawings
FIG. 1 is a schematic diagram of a bipolar capacitance type vacuum gauge;
FIG. 2 is a schematic illustration of a bipolar capacitance vacuum gauge with a diaphragm under force flexed;
FIG. 3 is a top view of a circular electrode and a ring electrode in a bipolar capacitance vacuum gauge;
FIG. 4 is a schematic diagram of a measurement circuit of a bipolar capacitance vacuum gauge;
fig. 5 is a specific circuit diagram of a measurement circuit of the bipolar capacitance type vacuum gauge.
[ Reference numerals description ]
1: A housing; 11: a vacuum chamber; 12: a detection chamber; 13: a detection hole; 2: a membrane; 3: fixing the substrate; 31: an insulating layer; 4: a ring electrode; 5: a circular electrode; 6: a common-substrate bridge detection circuit; 7: an oscillating circuit; 71: an oscillation control circuit; 72: a bridge oscillating circuit; 73: an RC filter circuit; m1: a first diode; m2: a second diode; m3: a third diode; m4: and a fourth diode.
Detailed Description
The invention will be better explained by the following detailed description of the embodiments with reference to the drawings.
It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.
Furthermore, descriptions such as those referred to as "first," "second," and the like, are provided for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implying an order of magnitude of the indicated technical features in the present disclosure. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
In the present invention, unless specifically stated and limited otherwise, the terms "connected," "affixed," and the like are to be construed broadly, and for example, "affixed" may be a fixed connection, a removable connection, or an integral body; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
The invention provides a bipolar capacitance type vacuum gauge (shown in figures 1 to 3), which comprises a shell 1, a diaphragm 2, a fixed substrate 3 and a fixed electrode;
The diaphragm 2 is fixedly installed in the housing 1, in a preferred embodiment, the diaphragm 2 is installed in the housing 1 by adopting a welding installation mode, the diaphragm 2 divides the housing 1 into two parts, one side is a vacuum cavity 11, the other side is a detection cavity 12, the vacuum cavity 11 and the detection cavity 12 are two mutually independent cavities, and it should be noted that the diaphragm 2 can also adopt other installation modes as long as the interior of the housing 1 can be divided into two mutually independent cavities.
The fixed substrate 3 is fixedly arranged in the vacuum cavity 11, and a fixed electrode is arranged on the fixed substrate 3; the fixed electrode and the diaphragm 2 form two pole plates of a variable capacitor, the diaphragm 2 generates elastic deformation after being subjected to the pressure in the detection cavity 12, so that the distance between the diaphragm 2 and the fixed electrode changes, the capacitance on the fixed electrode also changes after the distance between the variable capacitor and the two pole plates changes, and the pressure in the detection cavity 12 can be calculated by measuring the change of the capacitance on the fixed electrode. The pressure measuring mode is only related to the pressure, is irrelevant to the composition of gas, and has higher measuring precision.
The fixed electrode comprises a ring electrode 4 and a circular electrode 5, the circular electrode 5 is positioned in the ring electrode 4, and a space is reserved between the circular electrode 5 and the ring electrode 4, in a preferred scheme, as shown in fig. 2 and 3, the circular electrode 5 and the ring electrode 4 are arranged on one side of the fixed substrate facing the membrane 2, an insulating layer 31 is arranged at the space between the circular electrode 5 and the ring electrode 4, the insulating layer 31 between the circular electrode 5 and the ring electrode 4 can be a ceramic insulating layer, and the ceramic insulating layer has a good insulating effect, so that mutual transfer of electrons between the circular electrode 5 and the ring electrode 4 is avoided.
As shown in fig. 2, when the pressure P 1>Pb is measured, the diaphragm 2 deforms due to the pressure difference (P 1-Pb) in the pressure gauge, causing a change in capacitance (C Inner part ) on the circular electrode and zero capacitance (C Outer part ) of the circular plate. From the capacitance formula c=k epsilon S/d:
Wherein:
p 1: measuring the pressure;
p b: the pressure of the reference pressure chamber of the high vacuum system (P b<10-3 Pa), i.e., the reference pressure;
c Inner part : capacitance on the circular electrode 5 when the diaphragm 2 is not stressed;
C Outer part : when the diaphragm 2 is not stressed, the capacitance on the annular electrode 4;
Epsilon: dielectric constant;
s: the effective area between the two polar plates of the flat capacitor;
K: an electrostatic force constant;
d: the distance between the two polar plates.
Then, as for the capacitance on the circular electrode 5, the distance change amount Δd Inner part ＝d0-d11 thereof under the measured pressure, the effective area of the circular electrode 5 with respect to the diaphragm 2 is S Round circle ;
The capacitance on the ring electrode 4 has a distance change Δd Outer part ＝d0-d21 under the measured pressure, and the effective area of the circular electrode 5 with respect to the diaphragm 2 is S Circular ring ;
d 0: the diaphragm 2 is a distance between the annular electrode 4 and the circular electrode 5 when being deformed;
d 11: when the membrane 2 is stressed and deformed, a gap between the membrane 2 and the circular electrode 5 is formed;
d 21: when the membrane 2 is stressed and deformed, a gap is formed between the membrane 2 and the annular electrode 4.
When the displacement of the diaphragm 2 changes: when the displacement of the diaphragm 2 relative to the circular electrode 5 is Δd Inner part , a gap d 11＝d0-Δd Inner part between the diaphragm 2 and the circular electrode 5; when the displacement of the diaphragm 2 relative to the annular electrode 4 is Δd Outer part , a gap d 21＝d0-Δd Outer part between the diaphragm 2 and the circular electrode 4; at this time, the corresponding capacitance of the circular electrode isThe corresponding capacitance of the circular ring plate at the moment is/>
Then:
the relative amounts of change in capacitance values on the circular electrode 5 and the ring electrode 4 are respectively:
When Δd Inner part /d0 < <1, Δc Inner part /C Inner part ≈Δd Inner part d0;
Similarly when Δd Outer part /d0 < <1, Δc Outer part /C Outer part ≈Δd Outer part /d0;
Then deltac Inner part /C Inner part and deltad Inner part /d0、ΔC Inner part /C Inner part and deltad Inner part /d0 are approximately linear.
The invention provides the precision of a bipolar capacitance type vacuum gauge:
And the precision K Single sheet ＝Δd/d0 of the single electrode film vacuum gauge.
Compared with the precision K Single sheet of the single-electrode film vacuum gauge, the precision K Double-piece of the double-electrode capacitance vacuum gauge provided by the invention is improved by nearly two times.
Considering the linear term and the cubic term in ΔC/C 0, the relative linear error r is approximated as:
When/> Time of day
Considering the linear term and quadratic term in ΔC/C 0, then:
The relative nonlinear error of the bipolar capacitance gauge:
relative nonlinear error of monopole capacitance type vacuum gauge in prior art
R Single sheet ＞r Double-piece , the measurement of the bipolar capacitance type vacuum gauge is more accurate.
The detection cavity 12 is provided with a detection hole 13 for detecting pressure, the detection hole 13 is communicated with the detection cavity 12, the detection hole 13 is set to be in an open state, and the diaphragm 2 can detect the pressure in the detection cavity 12; the detection hole 13 is communicated with the outside and the detection cavity 12, is convenient for detection operation, and has a simple structure.
When the diaphragm 2 is deformed under force, the distance change amount relative to the annular electrode 4 is Δd Outer part , the distance change amount relative to the circular electrode 5 is Δd Inner part , and when the materials of the diaphragm 2 are different and the mounting modes of the diaphragm 2 are different, the distance change of the diaphragm 2 relative to the circular electrode 5 and the annular electrode 4 is also different when the diaphragm 2 is deformed under force, but the influence of null shift on a measuring circuit can be effectively reduced by setting the ratio of the area S Round circle of the circular electrode 5 to the area S Circular ring of the annular electrode 4 to be equal to the ratio of Δd Inner part to the Δd Outer part .
In a preferred embodiment, the ratio of the area S Round circle of the circular electrode 5 to the area S Circular ring of the ring electrode 4 is set to 1:1 to 1.5:1, the influence of zero drift on a measuring circuit can be effectively reduced. This is because during the forced deflection of the membrane 2When (1):
because the diaphragm 2 is mounted in the housing 1, the mounting process can be welding, riveting, etc., stress concentration and uneven deformation due to stress can be generated at the mounting position of the diaphragm 2 and the housing 1, thereby generating edge effect, and the ratio of the area S Round circle of the circular electrode 5 to the area S Circular ring of the annular electrode 4 is equal to The problem of consistency of the ratio of the internal capacitance to the external capacitance variation is solved structurally, the edge effect is eliminated, and the problem of zero drift stability is solved.
Meanwhile, the diaphragm 2 was a circular diaphragm, and the ratio of the outer diameter of the ring electrode 4 to the diameter of the diaphragm 2 was 0.7:1 to 1:1, the outer diameter of the annular electrode 4 and the diaphragm 2 are parallel to the fixed substrate 3 when no stress is applied, so that the measuring range of the bipolar capacitance type vacuum gauge is enlarged.
The membrane 2 is preferably made of a nickel-based alloy film, so that the membrane 2 has better corrosion resistance and can be applied to complex environments.
As shown in fig. 4, a measuring circuit for measuring the pressure in the detection chamber 12 in the bipolar capacitance type vacuum gauge includes a common-base bridge detection circuit 6 and an oscillation circuit 7.
The common-substrate bridge detection circuit 6 is connected to the circular electrode 5 and the ring electrode 4, and the common-substrate bridge detection circuit 6 outputs an induced voltage according to the capacitance variation amounts on the circular electrode 5 and the ring electrode 4.
The common-substrate bridge detection circuit 6 is connected with the oscillation circuit 7, the oscillation circuit 7 outputs a sine wave corresponding to the induced voltage according to the induced voltage, the amplitude of the sine wave corresponds to the magnitude of the induced voltage, and the frequency of the sine wave corresponds to the frequency of the induced voltage.
The common-substrate bridge detection circuit 6 comprises a first diode M1, a second diode M2, a third diode M3 and a fourth diode M4, wherein the first diode M1, the second diode M2, the third diode M3 and the fourth diode M4 are sequentially connected end to form a closed loop;
in a preferred embodiment, four diodes of the common base bridge detector circuit 6 are integrated on a common monolithic substrate, with six diodes being used independently and the sixth diode sharing a common terminal (referred to as the common ground in this circuit).
The common-substrate bridge detection circuit 6 comprises a first input end Vin1 and a second input end Vin2, wherein the first input end Vin1 is positioned at the joint of the first diode M1 and the second diode M2, and the second input end Vin2 is positioned at the joint of the third diode M3 and the fourth diode M4;
The common-substrate bridge detection circuit 6 further includes a first output terminal Vout1 and a second output terminal Vout2, where the first output terminal Vout1 is located at a junction between the second diode M2 and the third diode M3, and the second output terminal Vout2 is located at a junction between the fourth diode M4 and the first diode M1.
The first input terminal Vin1 is connected to the ring electrode 4, the second input terminal Vin2 is connected to the circular electrode 5, and the first output terminal Vout1 and the second output terminal Vout2 are connected to the oscillating circuit 7.
For an external measurement circuit, the circuit of the design is the same as a single-stage capacitance type vacuum gauge in the prior art, and a voltage signal is required to be in direct proportion to delta C; but unlike the bipolar capacitance vacuum gauge of the present invention, the voltage signal is proportional to (Δc Inner part +ΔC Outer part ). To achieve the design objective, the relative amount of change in the capacitance value that is acquired is required. The invention designs a common-substrate bridge detection circuit 6 which is a circuit invented specially for a bipolar electric vacuum gauge to acquire capacitance variation (delta C Inner part +ΔC Outer part ) signals on a circular polar plate 5 and a ring polar plate 4.
The oscillating circuit 7 includes an oscillating control circuit 71 and a bridge oscillating circuit 72, as shown in fig. 4, the first output terminal Vout1 and the second output terminal Vout2 are combined into one total output terminal Vout3, the induced voltages flow to the bridge oscillating circuit 72 and the oscillating control circuit 71, respectively, and the bridge oscillating circuit 72 and the oscillating control circuit 71 generate two waves of the same frequency according to the induced voltages.
The oscillation control circuit 71 rectifies, filters, amplifies, and oscillates the induced voltage to generate an alternating voltage, the alternating voltage generated by the oscillation control circuit 71 is a sine wave with a certain amplitude and frequency, and the alternating voltage generated by the oscillation control circuit 71 flows to the bridge oscillation circuit 72. The bridge oscillation circuit 72 outputs a specific sinusoidal alternating voltage at point P based on the frequency of the induced voltage and the alternating voltage generated by the oscillation control circuit 71, the amplitude of the sinusoidal alternating voltage corresponding to the amplitude of the alternating voltage generated by the oscillation control circuit 71. The pressure in the vacuum gauge can be obtained by measuring the sine alternating voltage.
As shown in fig. 5, in a specific measurement circuit of the present invention, the oscillation control circuit 71 includes an operational amplifier LM308, a field effect device J232, and a plurality of resistors and capacitors; the bridge oscillating circuit 72 includes an operational amplifier NE5534 and a plurality of resistors and capacitors, and the operational amplifier NE5534 and the RC are connected in series and parallel to form an RC bridge oscillator; the total output terminal Vout3 of the common-substrate bridge detection circuit 6 is connected to the inverting input terminal of the operational amplifier LM308, and the operational amplifier LM308 amplifies the induced voltage input from the inverting input terminal of the operational amplifier LM 308. The total output end Vout3 of the common base bridge detection circuit 6 is also connected with the forward input end of the operational amplifier NE5534 through a frequency-selective network consisting of a resistor and a capacitor, the output end Vout4 of the operational amplifier LM308 is connected with the reverse input end of the operational amplifier NE5534 through a field effect device J232, the output end Vout5 of the operational amplifier NE5534 is connected with an RC filter circuit 73, and an output point P in the RC filter circuit 73 is the output end of the oscillating circuit 7. The voltage measured at point P is:
U＝UP*{(ΔC Inner part /C3)+(ΔC Outer part /C)2}；
Taking C 2＝C3, then u=u P*ΔC/C2;
Wherein U P is the input sine wave amplitude; Δc=Δc Inner part +ΔC Outer part ;
As shown in fig. 5, the initial values on C Inner part and C Outer part can also be accurately determined by adjusting the value of C1 in the present circuit.
Table 1 shows a comparison of the bipolar capacitance type vacuum gauge made according to the design of the present invention with the prior art single electrode capacitance type vacuum gauge in measuring data. Under the same environment, two vacuum gauges with the same measuring range measure the measured data when the actual values are zero position, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and full position of the measuring range and the zero drift condition of the vacuum gauge at the normal temperature of 27 ℃ after zeroing; and the precision grades of the two vacuum gauges are calculated.
TABLE 1
The percentages in Table 1 refer to the percentage of full scale, 0Pa to 1333.2Pa being the scale (scale range 0-10 Torr), 0Pa representing zero position, 1333.2Pa representing full scale, i.e. full position.
As can be seen from Table 1, the bipolar capacitance type vacuum gauge provided by the invention has the advantages that compared with the single-electrode capacitance type vacuum gauge in the prior art, the accuracy is greatly improved, and the influence of null shift is less.
It should be understood that the above description of the specific embodiments of the present invention is only for illustrating the technical route and features of the present invention, and is for enabling those skilled in the art to understand the present invention and implement it accordingly, but the present invention is not limited to the above-described specific embodiments. All changes or modifications that come within the scope of the appended claims are intended to be embraced therein.
Claims (7)
1. A measurement circuit for measuring pressure in a bipolar capacitance vacuum gauge, comprising:
the bipolar capacitance type vacuum gauge comprises a shell, a diaphragm, a fixed substrate and a fixed electrode;
The diaphragm is fixedly arranged in the shell, the diaphragm divides the shell into two parts, one side is a vacuum cavity, and the other side is a detection cavity;
The fixed substrate is fixedly arranged in the vacuum cavity, and the fixed electrode is arranged on the fixed substrate;
The fixed electrode comprises an annular electrode and a circular electrode, the circular electrode is positioned in the annular electrode, and a space is reserved between the circular electrode and the annular electrode;
the measuring circuit comprises a common-substrate bridge detection circuit and an oscillating circuit;
the common-substrate bridge detection circuit is connected with the circular electrode and the annular electrode, and outputs induction voltage according to capacitance variation on the circular electrode and the annular electrode;
The common-substrate bridge detection circuit is connected with the oscillation circuit, the oscillation circuit comprises an oscillation control circuit and a bridge oscillation circuit, the first output end and the second output end are combined into a total output end, and induced voltages respectively flow to the bridge oscillation circuit and the oscillation control circuit; the oscillation control circuit rectifies, filters, amplifies and oscillates the induced voltage to generate an alternating voltage, the alternating voltage generated by the oscillation control circuit is sine wave with certain amplitude and frequency, and the alternating voltage generated by the oscillation control circuit flows to the bridge type oscillation circuit; the bridge type oscillation circuit outputs sinusoidal alternating voltage according to the frequency of the induced voltage and the alternating voltage generated by the oscillation control circuit, and the pressure in the vacuum gauge can be obtained by measuring the sinusoidal alternating voltage;
the common-substrate bridge detection circuit comprises a first diode, a second diode, a third diode and a fourth diode, wherein the first diode, the second diode, the third diode and the fourth diode are sequentially connected end to form a closed loop;
The common-substrate bridge detection circuit comprises a first input end and a second input end, wherein the first input end is positioned at the joint of the first diode and the second diode, and the second input end is positioned at the joint of the third diode and the fourth diode;
The common-substrate bridge detection circuit further comprises a first output end and a second output end, wherein the first output end is positioned at the joint of the second diode and the third diode, and the second output end is positioned at the joint of the fourth diode and the first diode;
the first input end is connected with the annular electrode through a wire, the second input end is connected with the circular electrode, and the first output end and the second output end are connected with the oscillating circuit.
2. The measurement circuit of claim 1 wherein the sensing chamber is provided with a sensing aperture for sensing pressure.
3. The measurement circuit of claim 1, wherein the circular electrode and the ring electrode are provided on a side of the fixed substrate facing the diaphragm, and an insulating layer is provided at a space between the circular electrode and the ring electrode.
4. The measurement circuit of claim 1 wherein the diaphragm changes distance from the annular electrode by Δd Outer part and from the circular electrode by Δd Inner part when deformed by a force;
The area ratio of the circular electrode to the annular electrode is equal to the ratio of Δd Inner part to Δd Outer part .
5. The measurement circuit of claim 4 wherein the area ratio of the circular electrode to the annular electrode is 1:1 to 1.5:1.
6. The measurement circuit of any one of claims 1-5, wherein the diaphragm is a circular diaphragm and the ratio of the outer diameter of the ring electrode to the diameter of the diaphragm is 0.7:1 to 1:1.
7. The measurement circuit of any one of claims 1-5 wherein the diaphragm is parallel to the fixed substrate when unstressed.
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| CN113899494B (en) * | 2021-12-09 | 2022-03-18 | 北京晨晶电子有限公司 | Detection circuit of capacitance type film vacuum gauge, vacuum gauge and vacuum degree detection method |
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