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CN114111965A - Liquid level measuring sensor based on interdigital capacitor and liquid level measuring method - Google Patents

Liquid level measuring sensor based on interdigital capacitor and liquid level measuring method Download PDF

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Publication number
CN114111965A
CN114111965A CN202111593662.0A CN202111593662A CN114111965A CN 114111965 A CN114111965 A CN 114111965A CN 202111593662 A CN202111593662 A CN 202111593662A CN 114111965 A CN114111965 A CN 114111965A
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capacitor
value
capacitance
liquid level
interdigital
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Inventor
王冬雪
吴新文
高立亮
常文伟
刘冠宇
柴泽峰
苑飞
谭志军
郭倩倩
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Shandong Shengli Tonghai Group Dongying Tianlan Energy Saving Technology Co ltd
University of Jinan
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Shandong Shengli Tonghai Group Dongying Tianlan Energy Saving Technology Co ltd
University of Jinan
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Priority to CN202111593662.0A priority Critical patent/CN114111965A/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/26—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields
    • G01F23/263—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors

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  • Electromagnetism (AREA)
  • Thermal Sciences (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)

Abstract

The invention discloses a liquid level measuring sensor based on interdigital capacitors and a liquid level measuring method. The round tube insulating shell is very beneficial to sealing, the sealing cost of the sensor is greatly reduced, and the reliability of the sensor is improved. And the FPC is adopted to process the interdigital capacitor, and the FPC interdigital capacitor is tightly attached to the inner wall of the circular tube insulating shell by means of the elasticity of the FPC. And the FPC interdigital capacitor measures the dielectric constant of a medium outside the pipe through the insulating circular pipe, and calculates the interface of the liquid according to the dielectric constant. The FPC interdigital capacitor can be processed in batch, has better consistency, can improve the consistency of products, and has lower cost.

Description

Liquid level measuring sensor based on interdigital capacitor and liquid level measuring method
Technical Field
The invention relates to the technical field of liquid level (solid material level) and water content measurement, in particular to a liquid level measurement sensor and a liquid level measurement method based on interdigital capacitors.
Background
The capacitance type liquid level sensor is a variable medium type capacitor which utilizes the capacitance change caused by the change of the measured medium surface. Such sensors are typically mounted vertically within the container under test. The capacitance type liquid level sensor has the advantages of large dynamic range, high response speed, small zero drift, simple structure, strong adaptability and the like.
Capacitive sensor liquid level sensors typically have both parallel plate and coaxial capacitive types. The structure of the sensor is shown in fig. 1, and comprises a parallel plate type and a coaxial capacitance type, as shown in fig. 1a and 1b, wherein the most common sensor is a coaxial capacitance sensor, two coaxial inner and outer metal tubes with different diameters are generally adopted to form two polar plates of a capacitor, a certain gap is kept between the two metal tubes, the change of a liquid level interface causes the linear change of a capacitance value, and the liquid level of the liquid level can be calculated according to the capacitance value.
The measurement at a multiphase interface is limited because a single capacitor cannot resolve the multiphase interface. For example, the oil produced from an oil field is a three-phase mixture of oil, gas and water, and the production process is accompanied by the existence of silt. Usually, crude oil, oil-water emulsion, water and sludge blanket are arranged from the top to the bottom of the tank. In the petroleum exploitation link, the transfer tank, the settling tank, the crude oil dehydrator, the electric dehydrator, the buffer tank, the storage and transportation tank and other links need multi-phase liquid level measurement, so that oil-water separation control is facilitated, and data are provided for mastering the water content of crude oil and the yield of crude oil in the exploitation process.
The method mainly adopts a sectional type capacitance sensor aiming at the measurement of the multiphase interface, and the sectional type capacitance sensor can distinguish that each capacitor is positioned in a certain layer according to the numerical value of each capacitor, so as to calculate and distinguish the multiphase interface. The segmented capacitance sensor has high measurement precision, low cost and the most extensive research.
There are mainly 3 common arrangements of the segmented capacitive electrodes, as shown in fig. 2. Fig. 2a shows a symmetrical bipolar plate segmented capacitor structure, where both plates of each capacitor are symmetrical and have the same parameters. Fig. 2b shows a segmented capacitor structure with a common electrode. Fig. 2c shows a unipolar segmented capacitor structure, which uses the container wall as the common electrode of the segmented capacitor, and can only be used for metal containers.
For some longer containers, more segment capacitance is often required. For example, the height of some tanks in the crude oil gathering and transportation process is usually over 10 meters, and in order to improve the liquid level measurement accuracy as much as possible, a measurement scheme of sectional capacitance measurement is adopted, and the number of capacitors is usually dozens, and even possibly hundreds. Currently, the main problems faced by several segmented capacitance measurement schemes based on fig. 2 are as follows:
the capacitance measuring circuit is typically located outside the tank. A large number of lead wires are led out to the measuring circuit, which brings difficulty to the installation and maintenance of the measuring system. The capacitance lead is longer, the parasitic capacitance value is larger, and different capacitance lead lengths bring great inconvenience to measurement and data processing.
The sensors in fig. 2a) and 2b) have a great difficulty in sealing and processing the sensors because of the large number of electrodes and leads.
Fig. 2c) is easy to seal because of adopting a single-pole scheme, but the container wall is required to be used as an electrode of the capacitor, the measurement accuracy is poor, and the method can only be used for a metal container. This type of sensor has two drawbacks:
firstly, the shape of the tank body and the position of the sensor can influence the parameters of the sensor, so the parameters of the sensor with the structure need to be calibrated on site, and inconvenience is brought to installation and debugging.
Secondly, because the storage tank diameter is great, adopt the jar body as the electrode, the precision of sensor receives the influence, if jar internal wall is non-metallic material especially can't realize accurate measurement.
The dielectric constant of the liquid and the medium in the capacitance sensor is easily influenced by the change of the internal temperature of the container, so that larger temperature drift is caused, and the measurement precision is influenced.
In the measurement process of crude oil and other comparatively dirty liquids, if polytetrafluoroethylene materials are not adopted, oil is easily hung on the surface of the segmented capacitance sensor, so that the capacitance value gradually deviates, and the measurement precision is influenced. The polytetrafluoroethylene has good anti-adhesion performance, and can better solve the problem of oil hanging when being used as an insulating material. However, almost all glues cannot firmly adhere to the teflon during adhesion, which brings sealing difficulty to the segmented capacitive sensor based on the teflon material.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the liquid level measuring sensor based on the interdigital capacitor and the liquid level measuring method, which have the advantages of convenient wiring, favorable sealing, improved product consistency and reduced cost.
In order to solve the technical problem, the technical scheme adopted by the invention is as follows: the utility model provides a liquid level measurement sensor based on interdigital electric capacity, includes insulating housing, sets up interdigital electric capacity and the electric capacity detection circuitry in insulating housing respectively, and the quantity of interdigital electric capacity is a plurality of, and a plurality of interdigital electric capacities distribute at insulating housing internal sectional type, and a plurality of interdigital electric capacities are connected to electric capacity detection circuitry through interdigital electric capacity lead wire, and electric capacity detection circuitry draws forth to the sensor outside through power and communication bus, and insulating housing both ends are sealed.
Furthermore, the insulating shell is an insulating circular tube, two electrodes of the interdigital capacitor are processed by adopting a flexible circuit board, and the interdigital capacitor is tightly attached to the inner wall of the insulating circular tube.
Furthermore, the insulating shell is made of polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkylvinylether copolymer, perfluoroethylene propylene copolymer or ethylene-tetrafluoroethylene copolymer.
Furthermore, the thickness of the flexible circuit board is more than 0.1 mm.
Furthermore, when the number of the interdigital capacitors is larger than a set value, a plurality of capacitor detection circuits are needed, and the plurality of capacitor detection circuits are cascaded together and connected to the same power supply and the same communication bus.
Furthermore, two ends of the insulating shell are sealed through insulating joints, or one end of the insulating shell is sealed through the insulating joints, and the other end of the insulating shell is sealed through welding.
The invention also discloses a liquid level measuring method, which is based on the liquid level measuring sensor and comprises the following steps:
s01), vertically placing the liquid level measurement sensor in a measured liquid level container, setting the number of interdigital capacitors in the liquid level measurement sensor to be n, wherein n is not less than 3, and numbering the capacitors from the top to the bottom in sequence as C1, C2, … … and Cn; c1 is ensured to be always in the air as reference environment capacitance and Cn is always in the liquid as reference liquid capacitance in the measurement process;
s02), before starting the measurement, measuring the value of each capacitor in the air respectively, and respectively recording as: ca1, Ca2, … …, Can; the value of each capacitance in the liquid is measured and recorded as: cl1, Cl2, … …, Cln;
s03), in the measuring process, firstly measuring the value of a reference capacitor C1, namely Cm1, wherein C1 is always in the air, and then measuring the value of a reference capacitor Cn, namely Cn1, wherein Cn is always in the liquid;
s04), correcting the value of each capacitor in the air caused by the environmental change according to the actually measured Cm1, and calculating the variation amount RATIOx of each capacitor, x being 1,2, … …, n according to the following formula:
Figure BDA0003428697310000021
wherein Cmx is a measured value of the x-th capacitor when the x-th capacitor works in the container, Cax is a calibrated value of the x-th capacitor in air, Clx is a calibrated value of the x-th capacitor in pure liquid, and Cmn is a measured value of the n-th capacitor in an actual working environment.
Figure BDA0003428697310000022
The value of the x-th capacitor in the air is subjected to parameter correction according to the calibration value Ca1 and the measured value Cm1 of C1,
Figure BDA0003428697310000031
the value of the x-th capacitor in the liquid is subjected to parameter correction according to the calibration value Cln and the measured value Cmn of the Cn;
s05), analyzing the capacitance positions of the liquid and air interfaces according to RATIOx, and analyzing the liquid interfaces in a mode of setting a threshold;
s06), analyzing the interface of two liquids with different dielectric constants of water and oil by setting a threshold value.
Further, in step S05), the threshold th1 and the threshold th2 are set, the value range of th1 is (0, 0.1), the value range of th2 is [0.9, 1],
1) when RATIOx < th1, the capacitor is considered to be in air;
2) when RATIOx > th2, the capacitor is considered to be in liquid;
3) when th1< RATIOx < th2, the capacitance is considered to be the interface between liquid and air.
Further, in step S06), the relative permittivity of water is set to εwaterThe relative dielectric constant of the oil is epsilonoilThe relative dielectric constant of air is epsilonairIt is known that the relative dielectric constant of water is much greater than that of oil at normal temperature, the dielectric constant of water is 20 times or more that of oil, the relative dielectric constant of air is about 1, epsilonwater>εoil>εair，
Introducing a marker position alpha, an acquisition formula of alpha is shown in (2),
Figure BDA0003428697310000032
cmx is the x-th capacitanceThe measured value of the capacitor in the container during working, Cax is the calibrated value of the x-th capacitor in the air, Cwx is the calibrated value of the x-th capacitor in the pure water, Cox is the calibrated value of the x-th capacitor in the pure oil, and the calibrated value alphaxwater＝Cwx-Cax；αxoil＝Cox-Cax；αxairEasy-to-get α per capacitance is calibrated at room temperature as 0xwa>αxoil>αxai，
Setting the value ranges of the threshold th1 and the thresholds th2 and th1 as (0, 0.1), the value range of th2 as [0.9, 1],
when RATIOx < th1, the capacitor is considered to be in air;
when RATIOx is used>th2, the alpha at that time is obtained, and
Figure BDA0003428697310000033
or
Figure BDA0003428697310000034
If it is
Figure BDA0003428697310000035
Or
Figure BDA0003428697310000036
A>0.05,1<B<20, the capacitor is considered to be in water, otherwise the capacitor is in oil;
when th1<RATIOx<th2, the alpha at that time is obtained, and
Figure BDA0003428697310000037
if it is
Figure BDA0003428697310000038
The capacitance is considered to be the interface of oil and water; otherwise, it is an oil and gas interface.
The invention has the beneficial effects that: the invention adopts a sectional type sensor structure, two electrodes of each capacitor are sealed in the same insulating shell, and the capacitor detection circuit is also arranged in the insulating shell, so that the interdigital capacitor and the capacitor detection circuit are convenient to wire. The round tube insulating shell is very beneficial to sealing, the sealing cost of the sensor is greatly reduced, and the reliability of the sensor is improved. And the FPC is adopted to process the interdigital capacitor, and the FPC interdigital capacitor is tightly attached to the inner wall of the circular tube insulating shell by means of the elasticity of the FPC. And the FPC interdigital capacitor measures the dielectric constant of a medium outside the pipe through the insulating circular pipe, and calculates the interface of the liquid according to the dielectric constant. The FPC interdigital capacitor can be processed in batch, has better consistency, can improve the consistency of products, and has lower cost.
Drawings
FIG. 1 is a schematic structural diagram of a conventional capacitive sensor;
FIG. 2 is a schematic structural diagram of a conventional segmented capacitive liquid level sensor;
FIG. 3 is a schematic structural diagram of an interdigital capacitor;
FIG. 4 is a schematic structural view of a liquid level measuring sensor according to embodiment 1;
FIG. 5 is a schematic top view of the level sensor of embodiment 1;
in the figure: 1. the device comprises a power supply and communication bus, 2, an upper sealing joint, 3, an insulating circular tube, 4, an interdigital capacitor, 5, a lower sealing joint, 6, an interdigital electrode, 7, a capacitor detection circuit, 8 and an interdigital capacitor electrode lead.
Detailed Description
The invention is further described with reference to the following figures and specific embodiments.
Example 1
This embodiment discloses a liquid level measuring sensor based on an interdigital capacitor, wherein the interdigital capacitor is manufactured by using a Flexible Printed Circuit (FPC), the basic structure of the interdigital capacitor is shown in fig. 3, a plurality of interdigital electrodes form two electrodes of the capacitor through conducting wires, because different substances have different dielectric constants, the change of the substance (generally liquid or solid powder) on the surface of the interdigital electrode causes the change of the capacitance value of the interdigital capacitor, the moisture content of sand, cement or other solid or liquid can be calculated according to the change of the capacitance value, the moisture content of the solid powder or liquid can also be calculated, the insulating shell is generally manufactured by using Polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), perfluoroethylene propylene copolymer (FEP) or ethylene-tetrafluoroethylene copolymer (ETFE), other insulating materials may also be used. The FPC interdigital capacitor can cling to the inner wall of the insulating circular tube by means of elasticity of the FPC interdigital capacitor. The FPC interdigital capacitor measures the dielectric constant of a medium outside the pipe through the insulating circular pipe, and calculates the interface of the liquid according to the dielectric constant.
As shown in fig. 4 and 5, the liquid level measurement sensor in this embodiment includes an insulating housing, a plurality of interdigital capacitors 4 and a capacitor detection circuit 7, which are respectively disposed in the insulating housing, where the number of the interdigital capacitors 4 is plural, the plurality of interdigital capacitors 4 are distributed in the insulating housing in a segmented manner, the plurality of interdigital capacitors 4 are connected to the capacitor detection circuit 7 through an interdigital capacitor electrode lead 8, the capacitor detection circuit 7 is led out to the outside of the sensor through a power supply and a communication bus 1, and two ends of the insulating housing are sealed.
In this embodiment, the insulating housing is an insulating circular tube 3, two electrodes of the interdigital capacitor 4 are processed by using a flexible circuit board, and the interdigital capacitor 4 is tightly attached to the inner wall of the insulating circular tube 3.
In order to ensure sufficient elasticity, the thickness of the flexible circuit board is more than 0.1 mm.
If the container of the measured liquid level is higher (or longer), more segmented capacitors are needed, and the number of the interdigital capacitors is larger than a set value, a plurality of capacitor detection circuits 7 are needed, and the plurality of capacitor detection circuits 7 are cascaded together and connected to the same power supply and the communication bus 1.
In the present embodiment, both ends of the insulating circular tube 3 are sealed by the upper insulating joint 2 and the lower insulating joint 5, respectively, and in other embodiments, if the material allows, one end of the insulating circular tube 3 is sealed by the insulating joint and the other end is sealed by welding.
Example 2
The embodiment discloses a liquid level measuring method, which is based on the liquid level measuring sensor and comprises the following steps:
s01), vertically placing the liquid level measurement sensor in a measured liquid level container, setting the number of interdigital capacitors in the liquid level measurement sensor to be n, wherein n is not less than 3, and numbering the capacitors from the top to the bottom in sequence as C1, C2, … … and Cn; c1 is ensured to be always in the air as reference environment capacitance and Cn is always in the liquid as reference liquid capacitance in the measurement process;
s02), before starting the measurement, measuring the value of each capacitor in the air respectively, and respectively recording as: ca1, Ca2, … …, Can; the value of each capacitance in the liquid is measured and recorded as: cl1, Cl2, … …, Cln;
s03), in the measuring process, firstly measuring the value of a reference capacitor C1, namely Cm1, wherein C1 is always in the air, and then measuring the value of a reference capacitor Cn, namely Cn1, wherein Cn is always in the liquid;
s04), correcting the value of each capacitor in the air caused by the environmental change according to the actually measured Cm1, and calculating the variation amount RATIOx of each capacitor, x being 1,2, … …, n according to the following formula:
Figure BDA0003428697310000051
wherein Cmx is a measured value of the x-th capacitor when the x-th capacitor works in the container, Cax is a calibrated value of the x-th capacitor in air, Clx is a calibrated value of the x-th capacitor in pure liquid, Cmn is a measured value of the n-th capacitor in an actual working environment,
Figure BDA0003428697310000052
the value of the x-th capacitor in the air is subjected to parameter correction according to the calibration value Ca1 and the measured value Cm1 of C1,
Figure BDA0003428697310000053
the value of the x-th capacitor in the liquid is subjected to parameter correction according to the calibration value Cln and the measured value Cmn of the Cn;
s05), analyzing the capacitance positions of the liquid and air interfaces according to RATIOx, and analyzing the liquid interfaces in a mode of setting a threshold;
s06), analyzing the interface of two liquids with different dielectric constants of water and oil by setting a threshold value.
In step S05) of this embodiment, the threshold th1 and the threshold th2 are set, the value range of th1 is (0, 0.1), the value range of th2 is [0.9, 1],
when RATIOx < th1, the capacitor is considered to be in air;
when RATIOx > th2, the capacitor is considered to be in liquid;
when th1< RATIOx < th2, the capacitance is considered to be the interface between liquid and air.
In this example, step S06), the relative permittivity of water is assumed to be ∈waterThe relative dielectric constant of the oil is epsilonoilThe relative dielectric constant of air is epsilonairIt is known that the relative dielectric constant of water is much greater than that of oil at normal temperature, the dielectric constant of water is 20 times or more that of oil, the relative dielectric constant of air is about 1, epsilonwater>εoil>εair，
Introducing a marker position alpha, an acquisition formula of alpha is shown in (2),
Figure BDA0003428697310000054
cmx is the measured value of the x-th capacitor when working in the container, Cax is the calibrated value of the x-th capacitor in the air, Cwx is the calibrated value of the x-th capacitor in the pure water, Cox is the calibrated value of the x-th capacitor in the pure oil, and the calibrated value alphaxwater＝Cwx-Cax；αxoil＝Cox-Cax；αxairEasy-to-get α per capacitance is calibrated at room temperature as 0xwa>αxoil>αxair，
Setting the value ranges of the threshold th1 and the thresholds th2 and th1 as (0, 0.1), the value range of th2 as [0.9, 1],
when RATIOx < th1, the capacitor is considered to be in air;
when RATIOx is used>th2, the alpha at that time is obtained, and
Figure BDA0003428697310000055
or
Figure BDA0003428697310000056
If it is
Figure BDA0003428697310000057
Or
Figure BDA0003428697310000058
A>0.05,1<B<20, the capacitor is considered to be in water, otherwise the capacitor is in oil;
when th1<RATIOx<th2, the alpha at that time is obtained, and
Figure BDA0003428697310000059
if it is
Figure BDA00034286973100000510
The capacitance is considered to be the interface of oil and water; otherwise, it is an oil and gas interface.
The foregoing description is only for the basic principle and the preferred embodiments of the present invention, and modifications and substitutions by those skilled in the art are included in the scope of the present invention.

Claims (9)

1.一种基于叉指电容的液位测量传感器，其特征在于：包括绝缘壳体、分别设置于绝缘壳体内的叉指电容和电容检测电路，叉指电容的数量为多个，多个叉指电容在绝缘壳体内分段式分布，多个叉指电容通过叉指电容引线连接至电容检测电路，电容检测电路通过电源及通信总线引出至传感器外部，绝缘壳体两端密封。1. a liquid level measuring sensor based on interdigital capacitance, it is characterized in that: comprise insulating housing, the interdigital capacitance and capacitance detection circuit that are respectively arranged in the insulating housing, the quantity of interdigital capacitance is a plurality of, a plurality of forks The finger capacitors are distributed in sections in the insulating shell. Multiple interdigital capacitors are connected to the capacitance detection circuit through the interdigitated capacitor leads. The capacitance detection circuit is led out of the sensor through the power supply and the communication bus. Both ends of the insulating shell are sealed. 2.根据权利要求1所述的基于叉指电容的液位测量传感器，其特征在于：绝缘壳体为绝缘圆形管，叉指电容的两个电极采用柔性电路板加工，叉指电容紧贴在绝缘圆形管的内壁。2. The liquid level measuring sensor based on interdigital capacitance according to claim 1, characterized in that: the insulating shell is an insulating circular tube, the two electrodes of the interdigital capacitor are processed by a flexible circuit board, and the interdigital capacitor is closely attached on the inner wall of the insulated circular tube. 3.根据权利要求1所述的基于叉指电容的液位测量传感器，其特征在于：绝缘壳体的材质为聚四氟乙烯、四氟乙烯—全氟烷氧基乙烯基醚共聚物、全氟乙烯丙烯共聚物或者乙烯-四氟乙烯共聚物。3. The liquid level measuring sensor based on interdigital capacitance according to claim 1, wherein the insulating shell is made of polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, Fluoroethylene propylene copolymer or ethylene-tetrafluoroethylene copolymer. 4.根据权利要求2所述的基于叉指电容的液位测量传感器，其特征在于：柔性电路板的厚度在0.1mm以上。4 . The liquid level measurement sensor based on interdigital capacitance according to claim 2 , wherein the thickness of the flexible circuit board is more than 0.1 mm. 5 . 5.根据权利要求1所述的基于叉指电容的液位测量传感器，其特征在于：叉指电容数量大于设定值时，需要多个电容检测电路，多个电容检测电路级联在一起，并连接到同一个电源和通信总线上。5. The liquid level measuring sensor based on interdigital capacitance according to claim 1, characterized in that: when the number of interdigital capacitances is greater than the set value, a plurality of capacitance detection circuits are required, and a plurality of capacitance detection circuits are cascaded together, and connected to the same power and communication bus. 6.根据权利要求1所述的基于叉指电容的液位测量传感器，其特征在于：绝缘壳体两端通过绝缘接头密封，或者绝缘壳体一端通过绝缘接头密封，另一端通过焊接密封。6 . The liquid level measuring sensor based on interdigital capacitance according to claim 1 , wherein both ends of the insulating housing are sealed by insulating joints, or one end of the insulating housing is sealed by insulating joints, and the other end is sealed by welding. 7 . 7.一种液位测量方法，其特征在于：本方法基于权利要求1所述的液位测量传感器，包括以下步骤：7. A liquid level measurement method, characterized in that: the method is based on the liquid level measurement sensor of claim 1, comprising the following steps: S01)、将液位测量传感器垂直放置在被测液位容器内，设液位测量传感器内的叉指电容数量为n，n≧3，自最上端到最底部，电容的编号依次为C1，C2，……，Cn；测量过程中保证C1始终在空气中，作为参考环境电容，Cn始终在液体中，作为参考液体电容；S01), place the liquid level measurement sensor vertically in the liquid level container to be measured, and set the number of interdigital capacitors in the liquid level measurement sensor to be n, n≧3, from the top to the bottom, the capacitors are serially numbered C1, C2, ..., Cn; during the measurement process, ensure that C1 is always in the air, as the reference ambient capacitance, Cn is always in the liquid, as the reference liquid capacitance; S02)、在开始测量之前，分别测量每个电容在空气中的数值，分别记为：Ca1，Ca2，……，Can；分别测量每个电容在液体中的数值，分别记为：Cl1，Cl2，……，Cln；S02), before starting the measurement, measure the value of each capacitor in the air, respectively: Ca1, Ca2, ..., Can; respectively measure the value of each capacitor in the liquid, respectively: Cl1, Cl2 , ..., Cln; S03)、在测量过程中首先测量参考电容C1的数值，记为Cm1，C1始终在空气中，再测量参考电容Cn的数值，记为Cn1，Cn始终在液体中；S03), in the measurement process, first measure the value of the reference capacitor C1, denoted as Cm1, C1 is always in the air, and then measure the value of the reference capacitor Cn, denoted as Cn1, Cn is always in the liquid; S04)、根据实际测量的Cm1来修正环境参数变化引起的每个电容数值变化，根据下面公式分别计算每个电容的变化量RATIOx，x＝1,2,……,n：S04), correct the change of each capacitance value caused by the change of environmental parameters according to the actual measured Cm1, and calculate the change amount of each capacitance RATIOx according to the following formula, x=1,2,...,n:
Figure FDA0003428697300000011
Figure FDA0003428697300000011
 其中Cmx为第x个电容在容器内工作时的测量值，Cax为第x个电容在空气中的标定值，Clx为第x个电容在纯液体中的标定值，Cmn为第n个电容在实际工作环境中的测量值；Where Cmx is the measured value of the xth capacitor working in the container, Cax is the calibration value of the xth capacitor in air, Clx is the calibration value of the xth capacitor in pure liquid, Cmn is the nth capacitor in the measured values in the actual working environment;
Figure FDA0003428697300000012
是根据C1的标定值Ca1和测量值Cm1对第x个电容在空气中的数值进行参数修正，
Figure FDA0003428697300000013
是根据Cn的标定值Cln和测量值Cmn对第x个电容在液体中的数值进行参数修正；
Figure FDA0003428697300000012
It is to correct the value of the xth capacitor in air according to the calibration value Ca1 of C1 and the measured value Cm1,
Figure FDA0003428697300000013
It is to correct the value of the xth capacitor in the liquid according to the calibration value Cln of Cn and the measured value Cmn; S05)、根据RATIOx分析液体和空气界面所在电容位置，可采用设置阈值的方式分析液体界面；S05), according to the RATIOx analysis liquid and air interface capacitance position, can adopt the mode of setting threshold to analyze liquid interface; S06)、通过设置阈值的方式分析水和油两种不同介电常数的液体的界面。S06), analyzing the interface of two liquids with different dielectric constants, water and oil, by setting a threshold value. 8.根据权利要求7所述的液位测量方法，其特征在于：步骤S05)中，设置阈值th1和阈值th2，th1的取值范围为(0,0.1]，th2的取值范围为[0.9,1)，8. The liquid level measurement method according to claim 7, characterized in that: in step S05), a threshold value th1 and a threshold value th2 are set, the value range of th1 is (0, 0.1], and the value range of th2 is [0.9 ,1), 当RATIOx<th1时，认为该电容处在空气中；When RATIOx<th1, the capacitor is considered to be in the air; 当RATIOx>th2时，认为该电容处在液体中；When RATIOx>th2, the capacitor is considered to be in liquid; 当th1<RATIOx<th2时，认为该电容为液体和空气的分界面。When th1<RATIOx<th2, the capacitance is considered to be the interface between liquid and air. 9.根据权利要求7所述的液位测量方法，其特征在于：步骤S06)中，设水的相对介电常数为εwater，油的相对介电常数为εoil，空气的相对介电常数为εair，已知常温下水的相对介电常数远大于油的介电常数，水的介电常数是油的介电常数的20倍以上，空气的相对介电常数约为1，εwater>εoil>εair，9. liquid level measuring method according to claim 7, is characterized in that: in step S06), set the relative permittivity of water to be ε water , the relative permittivity of oil to be ε oil , and the relative permittivity of air is ε air , it is known that the relative permittivity of water at room temperature is much larger than that of oil, the permittivity of water is more than 20 times that of oil, the relative permittivity of air is about 1, and ε water > ε oil >ε air , 引入一个标志位α，α的求取见式(2)，A flag bit α is introduced, and the calculation of α is shown in formula (2),
Figure FDA0003428697300000021
Figure FDA0003428697300000021
 Cmx为第x个电容在容器内工作时测量值，Cax为第x个电容在空气中的标定值，Cwx为第x个电容在纯水中的标定值，Cox为第x个电容在纯油中的标定值，标定值αxwater＝Cwx-Cax；αxoil＝Cox-Cax；αxair＝0，在室温下，标定好每个电容的易得αxwate>αxoil>αxair，Cmx is the measured value of the xth capacitor working in the container, Cax is the calibration value of the xth capacitor in air, Cwx is the calibration value of the xth capacitor in pure water, Cox is the xth capacitor in pure oil The calibration value in , the calibration value α xwater =Cwx-Cax; α xoil =Cox-Cax; α xair =0, at room temperature, the easy-to-obtain α xwate >α xoil >α xair of each capacitor is calibrated, 设置阈值th1和阈值th2，th1的取值范围为(0,0.1]，th2的取值范围为[0.9,1)，Set the threshold th1 and threshold th2, the value range of th1 is (0, 0.1], the value range of th2 is [0.9, 1), 当RATIOx<th1时，认为该电容处在空气中；When RATIOx<th1, the capacitor is considered to be in the air; 当RATIOx>th2时，求取此时的α，求取
Figure FDA0003428697300000022
或
Figure FDA0003428697300000023
若
Figure FDA0003428697300000024
或
Figure FDA0003428697300000025
A>0.05,1<B<20，认为该电容处在水中，否则该电容在油中；When RATIOx>th2, find the α at this time, find
Figure FDA0003428697300000022
or
Figure FDA0003428697300000023
like
Figure FDA0003428697300000024
or
Figure FDA0003428697300000025
A>0.05, 1<B<20, it is considered that the capacitor is in water, otherwise the capacitor is in oil; 当th1<RATIOx<th2时，求取此时的α，求取
Figure FDA0003428697300000026
若
Figure FDA0003428697300000027
认为该电容为油和水的分界面；否则为油和气的分界面。When th1<RATIOx<th2, find the α at this time, find
Figure FDA0003428697300000026
like
Figure FDA0003428697300000027
The capacitance is considered to be the interface between oil and water; otherwise, it is the interface between oil and gas.
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