CN103698612A - Online conductivity detection method - Google Patents

Abstract

The invention discloses an online conductivity detection method which is of a dual-parameter detection mode. The two parameters are phase difference and capacitance. The method comprises the following steps: densely winding enamelled copper wires on iron wires; then tightly winding three segments of the iron wires on a same plastic pipe so as to prepare three adjacent coaxial coils which are respectively one exciting coil and two induction coils, wherein a tested liquid flows in the plastic pipe. According to a phase difference detection method, the conductivity is calculated according to the functional relationship between the phase difference of two induced currents and the conductivity of the tested liquid; capacitance detection is realized by virtue of the exciting coil and two capacitance type sensors which are positioned on two sides of the exciting coil and formed by the induction coils, when the tested liquid flows into the plastic pipe, changes of output values of the capacitance type sensors are caused by the changes of the dielectric constants of the two capacitance type sensors, and the dielectric constant of the tested liquid is influenced by the change of the conductivity, so that the conductivity of the tested liquid is calculated according to a transfer function between the capacitance value and the conductivity.

Description

A kind of online conductivity detection method

Technical field

The present invention relates to a kind of online conductivity detection method that adopts electromagnetic field technology, for the on-line measurement to pipeline liquid electric conductivity.

Background technology

Conductivity sensor is general in industrial circle application.At present, most of conductivity is all the technology forming by detecting the conductive capability of electrolytic solution, concrete enforcement is to measure the conductance between two electrodes in conductance cell, and a major defect of this method is to have electrode electro Chemical reaction, thereby affects service precision and the life-span of electrode; In addition, traditional conductivity detects and mostly adopts single parameter to lead or inductance measurement as electricity, and the information redundancy of measuring system is low, and its reliability and robustness are subject to certain restrictions.Therefore,, when needs detect the conductivity of solution in pipeline continuously for a long time online, there is the defects such as cost performance is low, maintenance cost is high in prior art.

Summary of the invention

The object of the invention is in order to overcome the deficiencies in the prior art, the online conductivity detection method that a kind of cost performance is high, maintenance cost is low is provided.

The present invention is the detection mode of a kind of pair of parameter, and parameter is respectively phase differential and electric capacity.Detected device is: enamel covered wire is wrapped on iron wire thick and fast, then three sections of such iron wires are closely wrapped in respectively again and on same plastic tube outer wall, make three adjacent coaxial coils, thereby forming non-cpntact measurement structure, is mobile fluid to be measured in plastic tube.When fluid to be measured conductivity variations, will cause the change of phase differential between induced signal in pumping signal and inductive coil in drive coil, by the funtcional relationship between this phase differential and fluid to be measured conductivity, calculate conductivity size; Capacitance detecting is realized with two capacitance type sensors that the inductive coil of its both sides forms respectively by the drive coil as one of pole plate, when fluid to be measured flows into plastic tube, the specific inductive capacity of two capacitance type sensors that drive coil forms with inductive coil respectively can change, the change of specific inductive capacity can cause the variation of capacitive transducer electric capacity output valve, and the numerical values recited of fluid to be measured specific inductive capacity is subject to the impact of its conductivity variations just, by the funtcional relationship between this capacitive transducer electric capacity output valve and fluid to be measured conductivity, calculate conductivity size.

Beneficial effect of the present invention is that simple in structure, low cost of manufacture, information redundancy are high, and reliability and robustness are good.

Accompanying drawing explanation

The side-looking diagrammatic cross-section of the detected device of Fig. 1 the present invention;

In figure: 1. the first inductive coil; 2. drive coil; 3. the second inductive coil; 4. fluid to be measured; 5. enamel covered wire; 6. iron wire; 7. plastic tube.

Embodiment

Figure 1 shows that the side-looking diagrammatic cross-section of pick-up unit of the present invention, enamel covered wire 5 is wrapped on iron wire 6 thick and fast, then three sections of iron wires 6 that have been wound around enamel covered wire 5 are closely wrapped in respectively again and on same plastic tube 7 outer walls, make three adjacent coaxial coils i.e. the first inductive coil 1, the second inductive coil 3 and drive coil 2, thereby form non-cpntact measurement structure, be mobile fluid to be measured 4 in plastic tube 7.

When add exciting current i on drive coil 2 ₂=I _m2cos (ω t+ ψ ₂) after, just can on the first inductive coil 1, the second inductive coil 3, produce respectively induction current i ₁=I _m1cos (ω t+ ψ ₁) and i ₃=I _m3cos (ω t+ ψ ₃), induced signal i wherein ₁, i ₃with pumping signal i ₂the ψ of phase differential ₁₂=ψ ₁-ψ ₂, ψ ₃₂=ψ ₃-ψ ₂size can change along with fluid to be measured 4 conductivityσs' difference, between them, present certain funtcional relationship, function expression can carry out matching with following polynomial expression.

$\mathrm{\σ}=f({\mathrm{\ψ}}_{12},{\mathrm{\ψ}}_{32})={\mathrm{\α}}_0+{\mathrm{\α}}_1{\mathrm{\ψ}}_{12}+{\mathrm{\α}}_2{\mathrm{\ψ}}_{32}+{\mathrm{\α}}_3{\mathrm{\ψ}}_{12}{\mathrm{\ψ}}_{32}+{\mathrm{\α}}_4{\mathrm{\ψ}}_{12}^2+{\mathrm{\α}}_5{\mathrm{\ψ}}_{32}^2---\left(1\right)$

In formula, α ₀, α ₁, α ₂, α ₃, α ₄, α ₅for coefficient, they can utilize various known conductivity σ _j(j=0,1,2 ..., fluid to be measured n) and corresponding measure phase difference ψ thereof _12j, ψ _32j(j=0,1,2 ..., the experimental data base multivariate regression between n) is analyzed, and specifically by least square method, is calculated.

If the quadratic sum of observation data and matched curve (1) deviation is

$F({\mathrm{\α}}_0,{\mathrm{\α}}_1,{\mathrm{\α}}_2,{\mathrm{\α}}_3,{\mathrm{\α}}_4,{\mathrm{\α}}_5)=\underset{j=0}{\overset{n}{\mathrm{\Σ}}}{[{\mathrm{\σ}}_j-\mathrm{\σ}({\mathrm{\ψ}}_{12j},{\mathrm{\ψ}}_{32j})]}^2$

By $\frac{\∂F({\mathrm{\α}}_0,{\mathrm{\α}}_1,{\mathrm{\α}}_2,{\mathrm{\α}}_3,{\mathrm{\α}}_4,{\mathrm{\α}}_5)}{{\∂\mathrm{\α}}_k}=0,k=\mathrm{0,1,2,3,4,5}$

Obtain following system of equations:

$\left\{\begin{array}{c}\frac{\&PartialD;F({\mathrm{\&alpha;}}_0,{\mathrm{\&alpha;}}_1,{\mathrm{\&alpha;}}_2,{\mathrm{\&alpha;}}_3,{\mathrm{\&alpha;}}_4,{\mathrm{\&alpha;}}_5)}{\&PartialD;{\mathrm{\&alpha;}}_0}=2\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}[{\mathrm{\&sigma;}}_j-\mathrm{\&sigma;}({\mathrm{\&psi;}}_{12j},{\mathrm{\&psi;}}_{32j})]=0\\ \frac{\&PartialD;F({\mathrm{\&alpha;}}_0,{\mathrm{\&alpha;}}_1,{\mathrm{\&alpha;}}_2,{\mathrm{\&alpha;}}_3,{\mathrm{\&alpha;}}_4,{\mathrm{\&alpha;}}_5)}{\&PartialD;{\mathrm{\&alpha;}}_1}=2\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}[{\mathrm{\&sigma;}}_j-\mathrm{\&sigma;}({\mathrm{\&psi;}}_{12j},{\mathrm{\&psi;}}_{32j})]{\mathrm{\&psi;}}_{12j}=0\\ \frac{\&PartialD;F({\mathrm{\&alpha;}}_0,{\mathrm{\&alpha;}}_1,{\mathrm{\&alpha;}}_2,{\mathrm{\&alpha;}}_3,{\mathrm{\&alpha;}}_4,{\mathrm{\&alpha;}}_5)}{\&PartialD;{\mathrm{\&alpha;}}_2}=2\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}[{\mathrm{\&sigma;}}_j-\mathrm{\&sigma;}({\mathrm{\&psi;}}_{12j},{\mathrm{\&psi;}}_{32j})]{\mathrm{\&psi;}}_{32j}=0\\ \frac{\&PartialD;F({\mathrm{\&alpha;}}_0,{\mathrm{\&alpha;}}_1,{\mathrm{\&alpha;}}_2,{\mathrm{\&alpha;}}_3,{\mathrm{\&alpha;}}_4,{\mathrm{\&alpha;}}_5)}{\&PartialD;{\mathrm{\&alpha;}}_3}=2\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}[{\mathrm{\&sigma;}}_j-\mathrm{\&sigma;}({\mathrm{\&psi;}}_{12j},{\mathrm{\&psi;}}_{32j})]{\mathrm{\&psi;}}_{12j}{\mathrm{\&psi;}}_{32}j=0\\ \frac{\&PartialD;F({\mathrm{\&alpha;}}_0,{\mathrm{\&alpha;}}_1,{\mathrm{\&alpha;}}_2,{\mathrm{\&alpha;}}_3,{\mathrm{\&alpha;}}_4,{\mathrm{\&alpha;}}_5)}{\&PartialD;{\mathrm{\&alpha;}}_4}=2\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}[{\mathrm{\&sigma;}}_j-\mathrm{\&sigma;}({\mathrm{\&psi;}}_{12j},{\mathrm{\&psi;}}_{32j})]{\mathrm{\&psi;}}_{12\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000449468170000011.png"\; state="\{\{state\}\}">j</figure-callout>}}^2=0\\ \frac{\&PartialD;F({\mathrm{\&alpha;}}_0,{\mathrm{\&alpha;}}_1,{\mathrm{\&alpha;}}_2,{\mathrm{\&alpha;}}_3,{\mathrm{\&alpha;}}_4,{\mathrm{\&alpha;}}_5)}{\&PartialD;{\mathrm{\&alpha;}}_5}=2\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}[{\mathrm{\&sigma;}}_j-\mathrm{\&sigma;}({\mathrm{\&psi;}}_{12j},{\mathrm{\&psi;}}_{32j})]{\mathrm{\&psi;}}_{32\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000449468170000011.png"\; state="\{\{state\}\}">j</figure-callout>}}^2=0\end{array}\right.$

Separate this system of equations and get final product to obtain α ₀, α ₁, α ₂, α ₃, α ₄, α ₅.

The present invention is on identical pick-up unit, another kind of detection method is also disclosed: drive coil 2 respectively with the first inductive coils 1, the second inductive coil 3 form two capacitance type sensors, when fluid to be measured 4 flows into plastic tube 7, the DIELECTRIC CONSTANT ε of two capacitance type sensors that drive coil 2 respectively with the first inductive coils 1, the second inductive coil 3 form can change, and the variation of DIELECTRIC CONSTANT ε has caused again capacitive transducer capacitance C ₁₂, C ₃₂variation, and the numerical values recited of DIELECTRIC CONSTANT ε is subject to the impact that fluid to be measured conductivityσ changes so C just ₁₂, C ₃₂changing Pattern and fluid to be measured conductivityσ exist funtcional relationship, this funtcional relationship can be carried out matching with following polynomial expression:

$\mathrm{\&sigma;}=f(C_{12},C_{32})={\mathrm{\&beta;}}_0+{\mathrm{\&beta;}}_1{C}_{12}+{\mathrm{\&beta;}}_2{C}_{32}+{\mathrm{\&beta;}}_3{C}_{12}{C}_{32}+{\mathrm{\&beta;}}_4{C}_{12}^2+{\mathrm{\&beta;}}_5{C}_{32}^2---\left(2\right)$

In formula, β ₀, β ₁, β ₂, β ₃, β ₄, β ₅for coefficient.β ₀, β ₁, β ₂, β ₃, β ₄, β ₅also can utilize aforesaid least square method by various known conductivity σ _j(j=0,1,2 ..., fluid to be measured n) and corresponding measurement capacitance C thereof _12j, C _32j(j=0,1,2 ..., the experimental data base multivariate regression analysis between n) obtains.

Claims (2)

1. an online conductivity detection method, is characterized in that adopting following steps:

1) be wrapped on iron wire (6) enamel covered wire (5) is intensive, then three sections of iron wires (6) that have been wound around enamel covered wire (5) being closely wrapped in respectively again and making three adjacent coaxial coils on the outer wall of same plastic tube (7) is inductive coil (1,3) and drive coil (2), is mobile fluid to be measured (4) in plastic tube (7);

2) on drive coil (2), add exciting current i ₂=I _m2cos (ω t+ ψ ₂), inductive coil produces respectively induction current i on (1,3) ₁=I _m1cos (ω t+ ψ ₁) and i ₃=I _m3cos (ω t+ ψ ₃), induced signal i wherein ₁, i ₃with pumping signal i ₂phase differential ψ ₁₂=ψ ₁-ψ ₂, ψ ₃₂=ψ ₃-ψ ₂size can be along with the conductivityσ's of fluid to be measured (4) difference and change, between them, present certain funtcional relationship, function expression polynomial expression

$\mathrm{\&sigma;}=f({\mathrm{\&psi;}}_{12},{\mathrm{\&psi;}}_{32})={\mathrm{\&alpha;}}_0+{\mathrm{\&alpha;}}_1{\mathrm{\&psi;}}_{12}+{\mathrm{\&alpha;}}_2{\mathrm{\&psi;}}_{32}+{\mathrm{\&alpha;}}_3{\mathrm{\&psi;}}_{12}{\mathrm{\&psi;}}_{32}+{\mathrm{\&alpha;}}_4{\mathrm{\&psi;}}_{12}^2+{\mathrm{\&alpha;}}_5{\mathrm{\&psi;}}_{32}^2$ Carry out matching, wherein, α ₀, α ₁, α ₂, α ₃, α ₄, α ₅for coefficient;

3) utilize known conductivity σ _j(j=0,1,2 ..., fluid to be measured n) and the corresponding phase differential ψ measuring thereof _12j, ψ _32j(j=0,1,2 ..., experimental data base multivariate regression n) is analyzed, and by least square method, calculates α ₀, α ₁, α ₂, α ₃, α ₄, α ₅;

4) according to step 2) in function expression $\mathrm{\&sigma;}=f({\mathrm{\&psi;}}_{12},{\mathrm{\&psi;}}_{32})={\mathrm{\&alpha;}}_0+{\mathrm{\&alpha;}}_1{\mathrm{\&psi;}}_{12}+{\mathrm{\&alpha;}}_2{\mathrm{\&psi;}}_{32}+{\mathrm{\&alpha;}}_3{\mathrm{\&psi;}}_{12}{\mathrm{\&psi;}}_{32}+{\mathrm{\&alpha;}}_4{\mathrm{\&psi;}}_{12}^2+{\mathrm{\&alpha;}}_5{\mathrm{\&psi;}}_{32}^2$ And phase differential ψ ₁₂, ψ ₃₂with the α calculating in step 3) ₀, α ₁, α ₂, α ₃, α ₄, α ₅, calculate conductivityσ.

2. an online conductivity detection method, is characterized in that adopting following steps:

1) be wrapped on iron wire (6) enamel covered wire (5) is intensive, then three sections of iron wires (6) that have been wound around enamel covered wire (5) being closely wrapped in respectively again and making three adjacent coaxial coils on the outer wall of same plastic tube (7) is inductive coil (1,3) and drive coil (2), is mobile fluid to be measured (4) in plastic tube (7);

2) drive coil (2) respectively and inductive coil (1,3) form two capacitance type sensors, when fluid to be measured (4) flows into plastic tube (7), the DIELECTRIC CONSTANT ε of two capacitance type sensors that drive coil (2) and inductive coil (1,3) form can change, and the variation of DIELECTRIC CONSTANT ε causes again capacitive transducer capacitance C ₁₂, C ₃₂variation, C ₁₂, C ₃₂changing Pattern and fluid to be measured conductivityσ exist funtcional relationship, function expression polynomial expression

$\mathrm{\&sigma;}=f(C_{12},C_{32})={\mathrm{\&beta;}}_0+{\mathrm{\&beta;}}_1{C}_{12}+{\mathrm{\&beta;}}_2{C}_{32}+{\mathrm{\&beta;}}_3{C}_{12}{C}_{32}+{\mathrm{\&beta;}}_4{C}_{12}^2+{\mathrm{\&beta;}}_5{C}_{32}^2$ Carry out matching, wherein, β ₀, β ₁, β ₂, β ₃, β ₄, β ₅for coefficient;

3) utilize known conductivity σ _j(j=0,1,2 ..., fluid to be measured n) and corresponding measurement capacitance C thereof _12j, C _32j(j=0,1,2 ..., experimental data base multivariate regression n) is analyzed, and by least square method, calculates β ₀, β ₁, β ₂, β ₃, β ₄, β ₅;

4) according to step 2) in function expression $\mathrm{\&sigma;}=f(C_{12},C_{32})={\mathrm{\&beta;}}_0+{\mathrm{\&beta;}}_1{C}_{12}+{\mathrm{\&beta;}}_2{C}_{32}+{\mathrm{\&beta;}}_3{C}_{12}{C}_{32}+{\mathrm{\&beta;}}_4{C}_{12}^2+{\mathrm{\&beta;}}_5{C}_{32}^2$ And measurement capacitance C ₁₂, C ₃₂with the β calculating in step 3) ₀, β ₁, β ₂, β ₃, β ₄, β ₅, calculate conductivityσ.

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