CN103017864A

CN103017864A - Tubular three-electrode capacitive liquid level detection sensor and detection method

Info

Publication number: CN103017864A
Application number: CN2012105512990A
Authority: CN
Inventors: 陆贵荣; 韩红芳; 陈树越
Original assignee: Changzhou University
Current assignee: Changzhou University
Priority date: 2012-12-18
Filing date: 2012-12-18
Publication date: 2013-04-03

Abstract

The invention discloses a tubular three-electrode capacitive liquid level detection sensor and a detection method, belonging to the technical field of detection. The invention has a capacitance three-parameter detection method, and the liquid level detection is completed by the fusion of a combined capacitive sensor composed of three electrode plates. When the container is in a static state, the three capacitive sensors can measure the liquid level in the container independently, and can also compare their measured values to comprehensively evaluate the liquid level in the container, which improves the redundancy, reliability and robustness of measurement information; When the container is in a moving state, since the sensor has a 3-electrode structure, its 3 measurement output capacitances provide sufficient information redundancy including the tilt of the container, etc., and the output capacitance values of the 3 sensors can be fused to evaluate the liquid level in the container. high and low. The invention has the advantages of simple structure, low manufacturing cost, high information redundancy, good reliability and robustness, and high precision.

Description

A tubular three-electrode capacitive liquid level detection sensor and detection method

技术领域technical field

本发明属于检测技术领域，更准确地说是涉及一种采用电场技术的液位检测传感器及方法，用于对动态容器中液位的评价。The invention belongs to the technical field of detection, and more precisely relates to a liquid level detection sensor and method using electric field technology for evaluating the liquid level in a dynamic container.

背景技术Background technique

目前，液位传感器在各种领域得到普遍应用，其中大部分液位检测都是面向静止容器而形成的技术，具体实施中有浮子液位计、超声波液位计、光纤液位计、差压式液位计、圆柱形两电极电容式液位计等。At present, liquid level sensors are widely used in various fields, and most of the liquid level detection technologies are formed for static containers. The specific implementation includes float level gauges, ultrasonic liquid level gauges, optical fiber Type liquid level gauge, cylindrical two-electrode capacitive liquid level gauge, etc.

但是，这些方法的一个重要缺陷是当容器处于动态（时而倾斜时而直立）之中时便不能精确检测，此时需要额外的针对容器倾斜的检测及误差补偿。另外，传统的液位检测大都采用单参数如单电容等测量，测量系统的信息冗余性低，其可靠性和鲁棒性受到一定的限制。However, an important defect of these methods is that when the container is dynamic (sometimes tilted and sometimes upright), it cannot be accurately detected, and additional detection and error compensation for container tilt are required at this time. In addition, most of the traditional liquid level detection adopts single parameter such as single capacitance measurement, the information redundancy of the measurement system is low, and its reliability and robustness are limited to a certain extent.

发明内容Contents of the invention

针对现有技术中的液位检测技术的不足，本发明提出了一种测量精度高、可靠性和鲁棒性好、可应用于动态容器中对容器倾斜干扰自补偿液位检测传感器及检测方法。Aiming at the deficiencies of the liquid level detection technology in the prior art, the present invention proposes a liquid level detection sensor and detection method with high measurement accuracy, good reliability and robustness, which can be applied to a dynamic container for container tilt interference self-compensation .

具体地说，本发明是采取以下的技术方案来实现的：一种管形三电极电容式液位检测传感器，包括三个相同尺寸的弧片形电极、圆柱形的塑料管、屏蔽层，屏蔽层附着在塑料管外壁，三个弧片形电极贴在塑料管内壁，三个弧片形电极两两之间沿塑料管内壁的间隔相等，各弧片形电极的高度和塑料管的高度相同，塑料管内注入被测液体。Specifically, the present invention is achieved by adopting the following technical solutions: a tubular three-electrode capacitive liquid level detection sensor, including three arc-shaped electrodes of the same size, a cylindrical plastic tube, a shielding layer, and a shielding layer. The layer is attached to the outer wall of the plastic tube, and the three arc-shaped electrodes are attached to the inner wall of the plastic tube. The intervals between the three arc-shaped electrodes along the inner wall of the plastic tube are equal, and the height of each arc-shaped electrode is the same as the height of the plastic tube. , inject the measured liquid into the plastic tube.

本发明进一步的特征在于：所述三个弧片形电极两两之间沿塑料管内壁的间隔为1毫米弧长。The further feature of the present invention is that: the distance between two of the three arc-shaped electrodes along the inner wall of the plastic tube is 1 mm arc length.

本发明还包括一种采用上述管形三电极电容式液位检测传感器进行液位检测的方法，其步骤为：先在塑料管内注入被测液体，然后测出三个弧片形电极两两之间的电容的值，再根据公式（1）得到被测液体的液位：The present invention also includes a liquid level detection method using the above-mentioned tubular three-electrode capacitive liquid level detection sensor. The value of the capacitance between them, and then according to the formula (1) to get the liquid level of the liquid to be measured:

L(C₁,C₂,C₃)＝α₀+α₁C₁+α₂C₂+α₃C₃ （1）L(C ₁ ,C ₂ ,C ₃ )＝α ₀ +α ₁ C ₁ +α ₂ C ₂ +α ₃ C ₃ (1)

上述公式（1）中，L是被测液体的液位，C₁、C₂、C₃是三个弧片形电极两两之间的电容，α₀,α₁,α₂,α₃为系数；In the above formula (1), L is the liquid level of the liquid to be measured, C ₁ , C ₂ , and C ₃ are the capacitances between the three arc-shaped electrodes, and α ₀ , α ₁ , α ₂ , α ₃ are coefficient;

其中，α₀,α₁,α₂,α₃可利用各种已知液位L_k,(k＝1,2,…,m)及其对应测出的电容值C_1k、C_2k、C_3k，(k＝1,2,…,m)采用最小二乘法计算得到，其过程如下：Among them, α ₀ , α ₁ , α ₂ , α ₃ can use various known liquid levels L _k , (k=1,2,…,m) and their corresponding measured capacitance values C _1k , C _2k , C _3k , (k=1,2,...,m) is calculated by the least square method, and the process is as follows:

设L_k和L(C_1k,C_2k,C_3k)之间的方差为：(Δ_k)²=[L_k-L(C_1k,C_2k,C_3k)]²，总共有m个液位测试点，则其均方差R如公式（2）所述：Suppose the variance between L _k and L(C _1k ,C _2k ,C _3k ) is: (Δ _k ) ² =[L _k -L(C _1k ,C _2k ,C _3k )] ² , there are m liquid bit test point, its mean square error R is as described in formula (2):

$R R = = \frac{11}{m m} {Σ Σ}_{k k = = 11}^{m m} {[[{L L}_{k k} - - L L (({C C}_{11 k k},, {C C}_{22 k k},, {C C}_{33 k k}))]]}^{22}$

$= = \frac{11}{m m} {Σ Σ}_{k k = = 11}^{m m} {[[{L L}_{k k} - - (({α α}_{00} + + {α α}_{11} {C C}_{11 k k} + + {α α}_{22} {C C}_{22 k k} + + {α α}_{33} {C C}_{33 k k}))]]}^{22}$

$= = f f (({α α}_{00},, {α α}_{11},, {α α}_{22},, {α α}_{33})) - - - - - - ((22))$

根据均方差R最小的原则得：According to the principle of the smallest mean square error R:

$\frac{&PartialD; &PartialD; R R}{&PartialD; &PartialD; {α α}_{00}} = = 00$ $\frac{&PartialD; &PartialD; R R}{&PartialD; &PartialD; {α α}_{11}} = = 00$ $\frac{&PartialD; &PartialD; R R}{&PartialD; &PartialD; {α α}_{22}} = = 00$ $\frac{&PartialD; &PartialD; R R}{&PartialD; &PartialD; {α α}_{33}} = = 00$

再把公式（2）带入上面4个等式分别对α₀,α₁,α₂,α₃求偏导运算并整理得：Then put the formula (2) into the above four equations to calculate the partial derivatives of α ₀ , α ₁ , α ₂ , and α ₃ respectively and arrange them as follows:

$\{\begin{matrix} {α α}_{00} m m + + {α α}_{11} {Σ Σ}_{k k = = 11}^{m m} {C C}_{11 k k} + + {α α}_{22} {Σ Σ}_{k k = = 11}^{m m} {C C}_{22 k k} + + {α α}_{33} {Σ Σ}_{k k = = 11}^{m m} {C C}_{33 k k} = = {Σ Σ}_{k k = = 11}^{m m} {L L}_{k k} \\ {α α}_{00} {Σ Σ}_{k k = = 11}^{m m} {C C}_{11 k k} + + {α α}_{11} {Σ Σ}_{k k = = 11}^{m m} {C C}_{11 k k}^{22} + + {α α}_{22} {Σ Σ}_{k k = = 11}^{m m} {C C}_{11 k k} {C C}_{22 k k} + + {α α}_{33} {Σ Σ}_{k k = = 11}^{m m} {C C}_{11 k k} {C C}_{33 k k} = = {Σ Σ}_{k k = = 11}^{m m} {C C}_{11 k k} {L L}_{k k} \\ {α α}_{00} {Σ Σ}_{k k = = 11}^{m m} {C C}_{22 k k} + + {α α}_{11} {Σ Σ}_{k k = = 11}^{m m} {C C}_{11 k k} {C C}_{22 k k} + + {α α}_{22} {Σ Σ}_{k k = = 11}^{m m} {C C}_{22 k k}^{22} + + {α α}_{33} {Σ Σ}_{k k = = 11}^{m m} {C C}_{22 k k} {C C}_{33 k k} = = {Σ Σ}_{k k = = 11}^{m m} {C C}_{22 k k} {L L}_{k k} \\ {α α}_{00} {Σ Σ}_{k k = = 11}^{m m} {C C}_{33 k k} + + {α α}_{11} {Σ Σ}_{k k = = 11}^{m m} {C C}_{11 k k} {C C}_{33 k k} + + {α α}_{22} {Σ Σ}_{k k = = 11}^{m m} {C C}_{22 k k} {C C}_{33 k k} + + {α α}_{33} {Σ Σ}_{k k = = 11}^{m m} {C C}_{33 k k}^{22} = = {Σ Σ}_{k k = = 11}^{m m} {C C}_{33 k k} {L L}_{k k} \end{matrix}\}$

最后解此以α₀,α₁,α₂,α₃为未知数的4元一次方程组以得到α₀,α₁,α₂,α₃的值。Finally, solve this four-variable linear equation system with α ₀ , α ₁ , α ₂ , α ₃ as unknowns to obtain the values of α ₀ , α ₁ , α ₂ , α ₃ .

本发明的有益效果如下：本发明具有电容三参量检测方式，液位检测由三极板组成的组合电容式传感器融合完成，具体融合过程可采用多维回归方法，即首先用多项式拟合一个液位评价公式，然后用已知液位的传感器输出电容值实验数据库和最小二乘法求得多项式中的系数，最后再采用该多项式来评价未知液位信息。当容器处于静止状态时，3个电容传感器均可单独测量容器内液位，也可比较它们的测量值来综合评价容器内液位，提高了测量信息冗余性，可靠性和鲁棒性；当容器处于运动状态（时而倾斜时而直立）时，由于传感器具有3电极结构，它的3个测量输出电容提供了包含容器倾斜状况等的足够信息冗余，可融合3个传感器的输出电容值来评价容器内液位的高低，从而达到在液位评价过程中对容器倾斜带来的干扰自补偿的效果，最终测量精度得到提高。本发明结构简单、制造成本低、信息冗余性高，可靠性和鲁棒性好，精度高。The beneficial effects of the present invention are as follows: the present invention has a capacitance three-parameter detection method, and the liquid level detection is completed by the fusion of a combined capacitive sensor composed of three pole plates. The specific fusion process can adopt a multidimensional regression method, that is, firstly use a polynomial to fit a liquid level Evaluate the formula, then use the sensor output capacitance value experimental database of the known liquid level and the least square method to obtain the coefficients in the polynomial, and finally use the polynomial to evaluate the unknown liquid level information. When the container is in a static state, the three capacitive sensors can measure the liquid level in the container independently, and can also compare their measured values to comprehensively evaluate the liquid level in the container, which improves the redundancy, reliability and robustness of measurement information; When the container is in a moving state (sometimes tilted and sometimes upright), since the sensor has a 3-electrode structure, its 3 measurement output capacitances provide sufficient information redundancy including the tilting status of the container, etc., and the output capacitance values of the 3 sensors can be fused. Evaluate the level of the liquid in the container, so as to achieve the effect of self-compensation for the interference caused by the tilt of the container during the evaluation of the liquid level, and finally improve the measurement accuracy. The invention has the advantages of simple structure, low manufacturing cost, high information redundancy, good reliability and robustness, and high precision.

附图说明Description of drawings

图1是本发明的俯视结构示意图。Fig. 1 is a top view structural diagram of the present invention.

图2本发明的侧视结构示意图。Fig. 2 is a schematic side view of the structure of the present invention.

以上图中，1为第一电极，2为第二电极，3.为第三电极，4为屏蔽层，5为塑料管，6为被测液体，C₁为第一电极1和第二电极2之间的电容，C₂为第二电极2和第三电极3之间的电容，C₃为第一电极1和第三电极3之间的电容。In the above figure, 1 is the first electrode, 2 is the second electrode, 3 is the third electrode, 4 is the shielding layer, 5 is the plastic tube, 6 is the measured liquid, C ₁ is the first electrode 1 and the second electrode 2, C ₂ is the capacitance between the second electrode 2 and the third electrode 3, and C ₃ is the capacitance between the first electrode 1 and the third electrode 3.

具体实施方式Detailed ways

下面结合附图，对本发明进行详细描述。The present invention will be described in detail below in conjunction with the accompanying drawings.

如图1、2所示，本发明的管形三电极电容式液位检测传感器，包括三个相同尺寸的弧片形电极第一电极1、第二电极2、第三电极3、圆柱形的塑料管5、屏蔽层4。屏蔽层4紧密附着在塑料管5外壁。第一电极1、第二电极2、第三电极3紧密贴在塑料管5内壁，第一电极1、第二电极2、第三电极3两两之间沿塑料管5内壁的间隔相等，两两电极间形成了3个电容传感器。第一电极1、第二电极2、第三电极3的高度和塑料管5高度相同。塑料管5内注入被测液体6。其中，第一电极1、第二电极2、第三电极3两两之间沿塑料管5内壁的间隔可具体设为1毫米弧长。As shown in Figures 1 and 2, the tubular three-electrode capacitive liquid level detection sensor of the present invention includes three arc-shaped electrodes of the same size, the first electrode 1, the second electrode 2, the third electrode 3, a cylindrical Plastic pipe 5, shielding layer 4. The shielding layer 4 is closely attached to the outer wall of the plastic pipe 5 . The first electrode 1, the second electrode 2, and the third electrode 3 are closely attached to the inner wall of the plastic pipe 5, and the intervals between the first electrode 1, the second electrode 2, and the third electrode 3 along the inner wall of the plastic pipe 5 are equal, and the two Three capacitive sensors are formed between the two electrodes. The height of the first electrode 1 , the second electrode 2 and the third electrode 3 is the same as that of the plastic tube 5 . The measured liquid 6 is injected into the plastic tube 5 . Wherein, the distance between the first electrode 1 , the second electrode 2 , and the third electrode 3 along the inner wall of the plastic tube 5 can be specifically set as an arc length of 1 mm.

本发明的管形三电极电容式液位检测传感器的原理在于，当被测液体6流入塑料管5内的空间时，第一电极1、第二电极2、第三电极3之间两两组成的电容传感器极板之间的电解质介电常数的改变引起了两极板之间电容的变化，这种电容的变化规律与被测液体6的液位存在函数关系，从而可以利用该关系检测被测液体6的液位。具体而言，它们之间的关系可用如下的多项式来拟合。The principle of the tubular three-electrode capacitive liquid level detection sensor of the present invention is that when the measured liquid 6 flows into the space in the plastic pipe 5, the first electrode 1, the second electrode 2, and the third electrode 3 are formed in pairs The change of the dielectric constant of the electrolyte between the plates of the capacitive sensor causes the change of the capacitance between the two plates, and there is a functional relationship between the change law of the capacitance and the liquid level of the measured liquid 6, so that the measured liquid can be detected by using this relationship Level of liquid 6. Specifically, the relationship between them can be fitted by the following polynomial.

L(C₁,C₂,C₃)＝α₀+α₁C₁+α₂C₂+α₃C₃ L(C ₁ ,C ₂ ,C ₃ )＝α ₀ +α ₁ C ₁ +α ₂ C ₂ +α ₃ C ₃

上述式中，L是被测液体6的液位，C₁、C₂、C₃分别是第一电极1和第二电极2、第二电极2和第三电极3、第一电极1和第三电极3之间的电容，α₀,α₁,α₂,α₃为系数。In the above formula, L is the liquid level of the measured liquid 6, C ₁ , C ₂ , and C ₃ are respectively the first electrode 1 and the second electrode 2, the second electrode 2 and the third electrode 3, the first electrode 1 and the second electrode The capacitance between the three electrodes 3, α ₀ , α ₁ , α ₂ , α ₃ are coefficients.

而α₀,α₁,α₂,α₃可利用各种已知液位L_k(k＝1,2,…,m)及其对应被测电容值C_1k、C_2k、C_3k，(k＝1,2,…,m)之间的实验数据库采用最小二乘法计算得到，具体过程如下：And α ₀ , α ₁ , α ₂ , α ₃ can use various known liquid levels L _k (k=1,2,...,m) and their corresponding measured capacitance values C _1k , C _2k , C _3k , ( The experimental database between k=1,2,...,m) is calculated by the least square method, and the specific process is as follows:

设L_k和L(C_1k,C_2k,C_3k)之间的方差为：(Δ_k)²=[L_k-L(C_1k,C_2k,C_3k)]²，总共有m个液位测试点，则其均方差R为：Suppose the variance between L _k and L(C _1k ,C _2k ,C _3k ) is: (Δ _k ) ² =[L _k -L(C _1k ,C _2k ,C _3k )] ² , there are m liquid bit test point, then its mean square error R is:

$= = f f (({α α}_{00},, {α α}_{11},, {α α}_{22},, {α α}_{33}))$

把均方差R的表达式带入上面4个等式分别对α₀,α₁,α₂,α₃求偏导运算并整理得：Bring the expression of the mean square error R into the above four equations to calculate the partial derivative operation for α ₀ , α ₁ , α ₂ , and α ₃ respectively and arrange them as follows:

最后解此以α₀,α₁,α₂,α₃为未知数的4元一次方程组得其标定值。Finally, the calibration value is obtained by solving the quadratic linear equation system with α ₀ , α ₁ , α ₂ , and α ₃ as unknowns.

因此，本发明采用上述管形三电极电容式液位检测传感器进行液位检测的方法为，先在塑料管5内注入被测液体6，然后测出第一电极1和第二电极2、第二电极2和第三电极3、第一电极1和第三电极3之间的电容的值，再根据所述电容与液位的关系表达式得到被测液体6的液位。Therefore, the present invention uses the above-mentioned tube-shaped three-electrode capacitive liquid level detection sensor to detect the liquid level as follows: first inject the measured liquid 6 into the plastic pipe 5, and then measure the first electrode 1, the second electrode 2, the second electrode The value of the capacitance between the second electrode 2 and the third electrode 3, the first electrode 1 and the third electrode 3, and then obtain the liquid level of the measured liquid 6 according to the relationship expression between the capacitance and the liquid level.

虽然本发明已以较佳实施例公开如上，但实施例并不是用来限定本发明的。在不脱离本发明之精神和范围内，所做的任何等效变化或润饰，同样属于本发明之保护范围。因此本发明的保护范围应当以本申请的权利要求所界定的内容为标准。Although the present invention has been disclosed above with preferred embodiments, the embodiments are not intended to limit the present invention. Any equivalent changes or modifications made without departing from the spirit and scope of the present invention also belong to the protection scope of the present invention. Therefore, the scope of protection of the present invention should be based on the content defined by the claims of this application.

Claims

1. one kind tubular three electrode capacitance formula liquid level detecting sensors, it is characterized in that: comprise the arc sheet shape electrode of three same sizes, columniform plastic tube, screen layer, screen layer is attached to plastic tube outer wall, three arc sheet shape electrode pastes are at plastic pipe inner wall, three arc sheet shape electrodes equate along the interval of plastic pipe inner wall between any two, the height of each arc sheet shape electrode is identical with the height of plastic tube, injects fluid to be measured in the plastic tube.

2. a kind of tubular three electrode capacitance formula liquid level detecting sensors according to claim 1 is characterized in that: described three arc sheet shape electrodes are between any two along the 1 millimeter arc length that is spaced apart of plastic pipe inner wall.

3. one kind is adopted the claims 1 or 2 described tubular three electrode capacitance formula liquid level detecting sensors to carry out the method that liquid level detects, it is characterized in that: in plastic tube, inject first fluid to be measured, then measure the value of three arc sheet shape electrodes electric capacity between any two, obtain again the liquid level of fluid to be measured according to formula (1):

（1）

In the above-mentioned formula (1), LThe liquid level of fluid to be measured, C ₁, C ₂, C ₃Three arc sheet shape electrodes electric capacity between any two,

Be coefficient;

Wherein,

Can utilize various known liquid levels L _k ,( k=1,2 ..., m) and the corresponding capacitance of measuring C _1k, C _2k, C _3k, ( k=1,2 ..., m) adopt least square method to calculate, its process is as follows:

If L _kWith L( C _1k, C _2k, C _3k) between variance be: (Δ _k) ²=[ L _k- L( C _1k, C _2k, C _3k)] ², total total mIndividual liquid level test point, then its mean square deviation RAs described in formula (2):

（2）

According to mean square deviation RMinimum principle gets:

Again formula (2) is brought into top 4 equatioies right respectively

Ask the local derviation computing and put in order:

Separate at last this with

For 4 yuan of linear function groups of unknown number to obtain

Value.