CN101650211A - Method and device for measuring conductive liquid level and conductivity based on double coils - Google Patents

Abstract

The invention belongs to the fields of measurement of liquid levels and conductivity of conductive liquid and relates to an electromagnetic sensor based on double coils. The sensor comprises two coaxial coils with different radiuses and is placed on the horizontal liquid level; the self-inductance values of the two coils can be obtained by applying current exciting signals on the coils respectively and measuring the induction voltage of the coils; and the liquid level and the conductivity of the conductive liquid can be obtained at the same time by an algorithm based on simple resolution. Theinvention can measure liquid in a non-contact way and can be used for monitoring the conductivity and the liquid level simultaneously in an oil/gas/water separating facility; in addition, the measurement of the invention in the liquid level and the conductivity has an important application in a plurality of earth geography and ocean projects.

Description

A kind of conductive liquid level and conductivity measuring method and device based on twin coil

Technical field

The invention belongs to conducting liquid level and conductivity measurement field, relate to a kind of conductive liquid level of the electromagnetic sensor based on twin coil and the measurement mechanism and the method for conductivity.

Background technology

In many commercial Application, water is an important process component.And under many circumstances, water conducts electricity.Such as, the process electrical conductivity of water can be up to 4 west door/rice in the submarine oil exploitation.Monitoring to conductivity and water level is the necessary condition that effectively operates the separated from petroleum facility.The measurement of water level and conductivity in the oceanographic engineering, also has very important use in many geophysicses in addition.Non-cpntact measurement is desirable selection in many occasions.In the existing achievement in research, many technology of utilizing electric capacity, radar, ultrasonic and laser technology to measure height of water level are arranged, the product of some contact type measurement conductivity is also arranged; But the neither one sensor can be measured water level and conductivity non-contactly simultaneously.Utilize electromagnetic sensor to be to the theoretical foundation that electrical conductivity of water carries out non-contact measurement, electromagnetic sensor can cause eddy current in water, and eddy current can change the impedance operator of sensor, therefore the size of eddy current and conductivity and water level all have relation, and the impedance operator by survey sensor is to know water level and conductivity by inference theoretically.A common coil can only provide a measurement data, and can't determine water level and conductivity simultaneously.

Summary of the invention

The objective of the invention is to overcome the above-mentioned deficiency of prior art, a kind of inductance type transducer and the measuring method thereof that can determine water level and conductivity simultaneously is provided.It uses two different radiis coil, come to determine simultaneously water level and conductivity based on the brief analysis model of a simplification.

The object of the present invention is achieved like this:

A kind of conductive liquid level and conductivity measuring apparatus based on twin coil, comprise dual coil electromagnetic sensor, current excitation signal generating unit, induced signal measuring unit, simulation gating switch, host computer, described dual coil electromagnetic sensor is made of two different coaxial coils of radius, be vertically placed on the top of the horizontal liquid level of conducting liquid to be measured, successively two coils are connected to the current excitation signal generating unit by host computer by the simulation gating switch, apply pumping signal respectively, utilize induced signal measuring unit measurement induced voltage separately.

As preferred implementation, the measurement mechanism based on the dual coil electromagnetic sensor of the present invention, described double-coil sensor are that ratio 1-200, radius is that two coaxial coils of 0.1-10 are formed by two numbers of turn; Coil is made of insulated conductor, and the diameter of coiling is 0.1mm-10mm.

The present invention provides a kind of measuring method that adopts above-mentioned measurement mechanism simultaneously, comprises the following steps:

(1) first coil simulated switch and chooses, and the load energizing current signal carries out data acquisition to the induced voltage on it, the inductive voltage value of gathering is obtained the self-induction L of first coil divided by the exciting current value again ₁, with L ₁Deduct

(2) the aerial original inductance value L of first coil ₁₀Obtain the inductance changing value Δ L that causes by conducting liquid ₁

(3) second coils simulated switch and choose, and the load energizing current signal carries out data acquisition to the induced voltage on it, the inductive voltage value of gathering are obtained the self-induction L of first coil divided by the exciting current value again ₂, with L ₂Deduct second aerial original inductance value L of coil ₂₀Obtain the inductance changing value Δ L that causes by conducting liquid ₂

(4) two inductance changing values are divided by and are expressed as the function of water level c, $\frac{\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">L</figure-callout>}}_1}{\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">L</figure-callout>}}_2}=\mathrm{const}\&CenterDot;\frac{(1-e^{-2{\mathrm{\&alpha;}}_{01}c})}{(1-e^{-2{\mathrm{\&alpha;}}_{02}c})}=f\left(c\right),$ Wherein ω is the angular frequency of pumping signal, constant $\mathrm{const}=\frac{\mathrm{\&Delta;}{L}_{01}{{\mathrm{\&alpha;}}_{02}}^2}{\mathrm{\&Delta;}{L}_{02}{{\mathrm{\&alpha;}}_{01}}^2},$ α ₀₁And α ₀₂Be respectively the parameter of coil 1 and 2, α ₀₁Choose and make function $f_1\left(x\right)=\frac{{{\mathrm{<figure-callout\; id="1"\; label="J"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">J</figure-callout>}}_1}^2\left(\mathrm{\&alpha;}{r}_1\right)}{{\mathrm{\&alpha;}}^6}{A}_1\left(\mathrm{\&alpha;}\right)$ Maximization, α ₀₂Choose and make $f_2\left(x\right)=\frac{{{\mathrm{<figure-callout\; id="1"\; label="J"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">J</figure-callout>}}_1}^2\left(\mathrm{\&alpha;}{r}_2\right)}{{\mathrm{\&alpha;}}^6}{A}_2\left(\mathrm{\&alpha;}\right)$ Maximization.Wherein $A_1\left(\mathrm{\&alpha;}\right)={(e^{-\mathrm{\&alpha;}{h}_{11}}-e^{-\mathrm{\&alpha;}{h}_{12}})}^2,$ $A_2\left(\mathrm{\&alpha;}\right)={(e^{-\mathrm{\&alpha;}{h}_{21}}-e^{-\mathrm{\&alpha;}{h}_{22}})}^2,$ J ₁(x) be first kind first-order bessel function, h ₁₁And h ₁₂Be respectively the bottom of coil 1 and the height of distance from top liquid level, h ₂₁And h ₂₂Be respectively the bottom of coil 2 and the height of distance from top liquid level, r1 and r2 are respectively the radiuses of two coils;

(5) determine water level $c=f^{-1}\left(\frac{\mathrm{\&Delta;}{L}_1\left(\mathrm{\&omega;}\right)}{\mathrm{\&Delta;}{L}_2\left(\mathrm{\&omega;}\right)}\right);$

(6) basis $\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">L</figure-callout>}}_1=\mathrm{<figure-callout\; id="1"\; label="const"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">const</figure-callout>}1\&CenterDot;\frac{\mathrm{j\&omega;\&sigma;}{\mathrm{\&mu;}}_0(1-{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{01}c})}{4{{\mathrm{\&alpha;}}_{01}}^2{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{01}c}}$ Formula is determined the conductivity.Here const1=Δ L ₀₁, μ ₀It is airborne magnetic permeability.

Apparatus and method of the present invention can non-cpntact measurement obtain the liquid level and the conductivity of conducting liquid, and very important use is also arranged in petroleum chemical industry, geophysics, oceanographic engineering.Can overcome the easy contaminated situation of touch sensor, it also can be used in the measurement of corrosive liquids.

Description of drawings

Fig. 1 is the electromagnetic sensing system and device synoptic diagram based on twin coil of the present invention;

Fig. 2 is a dual coil electromagnetic sensor synoptic diagram;

Fig. 3 is the square section synoptic diagram of two coaxial coils.

Specific implementation method

Below in conjunction with drawings and Examples the present invention is further described.

Fig. 1 is a kind of implemented according to the invention electromagnetic sensing system and device schematic diagram based on twin coil.It is made of two coaxial coils, data acquisition, three major parts of host computer, and wherein part of data acquisition has comprised signal generation, simulation gating switch, power amplification and signal condition and collection plurality of units.Signal generating unit can adopt Direct Digital to synthesize (DDS) chip AD7008, and this chip can produce the sinusoidal excitation signal of different amplitudes and phase place.The amplitude of pumping signal and phase place can be by computer installations, by being installed at after the power amplifier amplification on the drive coil by the analog switch gating.

Computer control signal conditioning and collecting unit are to the mutual inductance data acquisition of coil 1 and coil 2, and order is wherein controlled by analog switch.To the drive coil of needs, the electric current bearing value of analog switch should be between the 10mA to 1A analog switch with the signal allocation of power amplifier output.Analog switch can adopt the high-current switch chip (as MAX4656) of MAXIUM company.

Coil 1 and coil 2 are formed by the insulated conductor coiling, and the diameter of coiling is 0.1mm-10mm, and the number of turn of coiling is the 1-1000 circle, and the diameter of coil is 5mm-500mm.Coil former is that non-conducting material is made, such as plastics etc.

The form of dual coil electromagnetic sensor as shown in Figure 2, two coaxial coils are fixed on the top of the conducting liquid of surveying 1.In data acquisition, first coil 2 simulated switch earlier and chooses, the load energizing current signal, its induced voltage is sent into data acquisition board by amplification and demodulation and (is picked out two leads on each coil simultaneously, these two leads be the excitation input end also be to measure output terminal, because the measurement of the input of exciting current and self induction voltage is not disturbed mutually, can carry out simultaneously), induced voltage obtains the self-induction of this coil divided by exciting current.Afterwards, second coil 3 simulated switch and chooses, the load energizing current signal, and its induced voltage is sent into data acquisition board by amplifying with demodulation, and induced voltage obtains the self-induction of second coil divided by exciting current.After having obtained the self-induction of these two coils, can calculate liquid level and conductivity, this process is:

(1) first coil 2 simulated switch and chooses, and the load energizing current signal carries out data acquisition to the induced voltage on it, the inductive voltage value of gathering is obtained the self-induction L of first coil divided by the exciting current value again ₁, with L ₁Deduct the aerial original inductance value L of first coil ₁₀Obtain the inductance changing value Δ L that causes by conducting liquid ₁

(2) second coils 2 simulated switch and choose, and the load energizing current signal carries out data acquisition to the induced voltage on it, the inductive voltage value of gathering are obtained the self-induction L of first coil divided by the exciting current value again ₂, with L ₂Deduct second aerial original inductance value L of coil ₂₀Obtain the inductance changing value Δ L that causes by conducting liquid ₂

(3) two inductance changing values are divided by and are expressed as the function of water level c: $\frac{\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">L</figure-callout>}}_1}{\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">L</figure-callout>}}_2}=\mathrm{const}\&CenterDot;\frac{(1-e^{-2{\mathrm{\&alpha;}}_{01}c})}{(1-e^{-2{\mathrm{\&alpha;}}_{02}c})}=f\left(c\right),$ Wherein ω is the angular frequency of pumping signal, constant $\mathrm{const}=\frac{\mathrm{\&Delta;}{L}_{01}{{\mathrm{\&alpha;}}_{02}}^2}{\mathrm{\&Delta;}{L}_{02}{{\mathrm{\&alpha;}}_{01}}^2}.$ α wherein ₀₁And α ₀₂Be respectively the parameter of coil 1 and 2, α ₀₁Choose and make function $f_1\left(x\right)=\frac{{{\mathrm{<figure-callout\; id="1"\; label="J"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">J</figure-callout>}}_1}^2\left(\mathrm{\&alpha;}{r}_1\right)}{{\mathrm{\&alpha;}}^6}{A}_1\left(\mathrm{\&alpha;}\right)$ Maximization, α ₀₂Choose and make $f_2\left(x\right)=\frac{{{\mathrm{<figure-callout\; id="1"\; label="J"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">J</figure-callout>}}_1}^2\left(\mathrm{\&alpha;}{r}_2\right)}{{\mathrm{\&alpha;}}^6}{A}_2\left(\mathrm{\&alpha;}\right)$ Maximization.Wherein $A_1\left(\mathrm{\&alpha;}\right)={(e^{-\mathrm{\&alpha;}{h}_{11}}-e^{-\mathrm{\&alpha;}{h}_{12}})}^2,$ $A_2\left(\mathrm{\&alpha;}\right)={(e^{-\mathrm{\&alpha;}{h}_{21}}-e^{-\mathrm{\&alpha;}{h}_{22}})}^2,$ J ₁(x) be first kind first-order bessel function.The height of the bottom of coil 1 is h ₁₁, the height at coil 1 top is h ₁₂, coil 1 highly is L=h ₁₂-h ₁₁The height of the bottom of coil 2 is h ₂₁, the height at coil 2 tops is h ₂₂, coil 2 highly is L=h ₂₂-h ₂₁, r1 and r2 are respectively the radiuses of two coils, referring to Fig. 3;

(4) determine water level $c=f^{-1}\left(\frac{\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">L</figure-callout>}}_1}{\mathrm{\&Delta;}{L}_2}\right);$ Promptly find the solution and make $\frac{\mathrm{\&Delta;}{L}_1\left(\mathrm{\&omega;}\right)}{\mathrm{\&Delta;}{L}_2\left(\mathrm{\&omega;}\right)}-f\left(c\right)=0$ Water level c value; To this nonlinear function, the standard method of trying to achieve its zero point has Newton method, look-up table etc.

(5) basis $\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">L</figure-callout>}}_1=\mathrm{<figure-callout\; id="1"\; label="const"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">const</figure-callout>}1\&CenterDot;\frac{\mathrm{j\&omega;\&sigma;}{\mathrm{\&mu;}}_0(1-{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{01}c})}{4{{\mathrm{\&alpha;}}_{01}}^2{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{01}c}}$ Formula is determined the conductivity.Here const1=Δ L ₀₁, μ ₀It is airborne magnetic permeability.

The theoretical foundation of above-mentioned method is as follows:

(C.V.Dodd and W.E.Deeds are published in J.Appl.Phys. according to the theory of Dodd and Deeds, vol.39, pp.2829-2839, the article that is entitled as Analytical solutions to eddy-currentprobe-coil problem on 1968), the air-core circular coil is changed to by the inductance that conducting liquid causes on the conducting liquid plane

$\mathrm{\&Delta;L}=K{\&Integral;}_0^{\&infin;}\frac{{{\mathrm{<figure-callout\; id="1"\; label="J"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">J</figure-callout>}}_1}^2\left(\mathrm{\&alpha;}\right)}{{\mathrm{\&alpha;}}^6}A\left(\mathrm{\&alpha;}\right)\mathrm{\&phi;}\left(\mathrm{\&alpha;}\right)\mathrm{d\&alpha;}---\left(1\right)$

Wherein,

$\mathrm{\&phi;}\left(\mathrm{\&alpha;}\right)=\frac{\mathrm{j\&omega;\&sigma;}{\mathrm{\&mu;}}_0(1-{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{1}c})}{{({\mathrm{\&alpha;}}_1+\mathrm{\&alpha;})}^2{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{1}c}-{({\mathrm{\&alpha;}}_1-\mathrm{\&alpha;})}^2}---\left(2\right)$

${\mathrm{\&alpha;}}_1=\sqrt{{\mathrm{\&alpha;}}^2+\mathrm{j\&omega;\&sigma;}{\mathrm{\&mu;}}_0}---\left(3\right)$

$K=\frac{\mathrm{\&pi;}{\mathrm{\&mu;}}_0{N}^2}{{(h_1-h_2)}^2{(r_1-r_2)}^2}---\left(4\right)$

$A\left(\mathrm{\&alpha;}\right)={(e^{-\mathrm{\&alpha;}{h}_1}-e^{-\mathrm{\&alpha;}{h}_2})}^2---\left(5\right)$

Wherein, α is an integration parameter; ω is the angular frequency of pumping signal; σ and μ represent the conductivity and the magnetic permeability of conductive plane respectively; The height indicator of coil bottom is shown h ₁, the height indicator of coil top is shown h ₂, coil height is L=h ₂-h ₁The number of turn of coil is N, and internal diameter and external diameter are respectively r ₁And r ₂μ ₀Be airborne magnetic permeability, J ₁(x) be first kind first-order bessel function.

Below by two approximate expressions analytic solution are simplified.First approximate expression is based on the following fact, promptly φ (α) with the rate of change of α with respect to

Less, and

At a α ₀Be issued to its peak value, therefore, can be at α ₀The place shifts out integration with it, at this moment after calculating φ (α)

ΔL(ω)＝φ(α ₀)ΔL ₀ (6)

$\mathrm{\&phi;}\left({\mathrm{\&alpha;}}_0\right)=\frac{\mathrm{j\&omega;\&sigma;}{\mathrm{\&mu;}}_0(1-{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{1}c})}{{({\mathrm{\&alpha;}}_1+{\mathrm{\&alpha;}}_0)}^2{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{1}c}-{({\mathrm{\&alpha;}}_1-{\mathrm{\&alpha;}}_0)}^2}---\left(7\right)$

Consider in frequency be lower than 500kHz, conductivity is lower than under the situation of 10S/m, j ω σ μ ₀＜＜α ₀Set up, so

$\mathrm{\&Delta;L}=\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">L</figure-callout>}}_0\frac{\mathrm{j\&omega;\&sigma;}{\mathrm{\&mu;}}_0(1-{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{0}c})}{4{{\mathrm{\&alpha;}}_0}^2{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{0}c}}---\left(9\right)$

Following formula shows that the solid part signal of self-induction of loop changing value is minimum, almost can ignore, and linear proportional relation of the angular frequency of its imaginary signals and electrical conductivity of water, pumping signal and water level is nonlinear relationship.

If we use the coil of two different sizes, the self-induction of first coil can be expressed as so

$\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">L</figure-callout>}}_1=\mathrm{\&Delta;}{L}_{01}\frac{\mathrm{j\&omega;\&sigma;}{\mathrm{\&mu;}}_0(1-{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{01}c})}{4{{\mathrm{\&alpha;}}_{01}}^2{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{01}c}}---\left(10\right)$

The self-induction of second coil can be expressed as

$\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">L</figure-callout>}}_2=\mathrm{\&Delta;}{L}_{02}\frac{\mathrm{j\&omega;\&sigma;}{\mathrm{\&mu;}}_0(1-{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{02}c})}{4{{\mathrm{\&alpha;}}_{02}}^2{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{02}c}}---\left(11\right)$

After two formulas are divided by, two counteractings of the angular frequency of electrical conductivity of water, pumping signal,

$\frac{\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">L</figure-callout>}}_1}{\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">L</figure-callout>}}_2}=\frac{\mathrm{\&Delta;}{L}_{01}{{\mathrm{\&alpha;}}_{02}}^2(1-e^{-2{\mathrm{\&alpha;}}_{01}c})}{\mathrm{\&Delta;}{L}_{02}{{\mathrm{\&alpha;}}_{01}}^2(1-e^{-2{\mathrm{\&alpha;}}_{02}c})}=\mathrm{const}\&CenterDot;\frac{(1-e^{-2{\mathrm{\&alpha;}}_{01}c})}{(1-e^{-2{\mathrm{\&alpha;}}_{02}c})}---\left(12\right)$

Wherein

With the size of coil, the number of turn, it is relevant to lift from distance etc.

In following formula, for given sensor setting, water level is unique variable, therefore can be determined by unique.After water level is determined, conductivity can by $\mathrm{\&Delta;}{L}_1\left(\mathrm{\&omega;}\right)=\mathrm{\&Delta;}{L}_{01}\frac{\mathrm{j\&omega;\&sigma;}{\mathrm{\&mu;}}_0(1-{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{01}c})}{4{{\mathrm{\&alpha;}}_{01}}^2{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{01}c}}$ Or $\mathrm{\&Delta;}{L}_2\left(\mathrm{\&omega;}\right)=\mathrm{\&Delta;}{L}_{02}\frac{\mathrm{j\&omega;\&sigma;}{\mathrm{\&mu;}}_0(1-{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{02}c})}{4{{\mathrm{\&alpha;}}_{02}}^2{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="A2009100704360009H2.png"\; state="\{\{state\}\}">e</figure-callout>}}^{2{\mathrm{\&alpha;}}_{02}c}}$ And decide.

Experimental verification and result:

In order to verify above measurement mechanism and method, test.In experiment, two coaxial circular coils are positioned over top, horizontal salt solution plane.The salt solution plane is much larger than the size of coil.Utilize electric impedance analyzer (Agilent 4204) that the self-induction of two coils is measured.Measured by HANA HI8733 type electric conductivity instrument as the salt water conductivity with reference to value, water level is measured by the centimeter scale chi.Experimental data such as following table

The parameter of coil is respectively R ₁=150mm, r ₂=150.1mm, number of turn N=10.

The actual value of table water level and conductivity and measured value contrast

Claims (4)

1. conductive liquid level and conductivity measuring apparatus based on a twin coil, comprise the dual coil electromagnetic sensor, the current excitation signal generating unit, the induced signal measuring unit, the simulation gating switch, host computer, it is characterized in that, described dual coil electromagnetic sensor is made of two different coaxial coils of radius, be vertically placed on the top of the horizontal liquid level of conducting liquid to be measured, successively two coils are connected to the current excitation signal generating unit by host computer by the simulation gating switch, apply pumping signal respectively, utilize induced signal measuring unit measurement induced voltage separately.

2. the measurement mechanism based on the dual coil electromagnetic sensor according to claim 1 is characterized in that, described double-coil sensor is that ratio 1-200, radius is that two coaxial coils of 0.1-10 are formed by two numbers of turn.

3. the measurement mechanism based on the dual coil electromagnetic sensor according to claim 1 and 2 is characterized in that coil is made of insulated conductor, and the diameter of coiling is 0.1mm-10mm.

4. a measuring method that adopts claim 1 or 2 or 3 described measurement mechanisms based on the dual coil electromagnetic sensor is characterized in that, comprises the following steps:

(1) first coil simulated switch and chooses, and the load energizing current signal carries out data acquisition to the induced voltage on it, the inductive voltage value of gathering is obtained the self-induction L of first coil divided by the exciting current value again ₁, with L ₁Deduct the aerial original inductance value L of first coil ₁₀Obtain the inductance changing value Δ L that causes by conducting liquid ₁

(2) second coils simulated switch and choose, and the load energizing current signal carries out data acquisition to the induced voltage on it, the inductive voltage value of gathering are obtained the self-induction L of first coil divided by the exciting current value again ₂, with L ₂Deduct second aerial original inductance value L of coil ₂₀Obtain the inductance changing value Δ L that causes by conducting liquid ₂

(3) two inductance changing values are divided by and are expressed as the function of water level c,

Wherein ω is the angular frequency of pumping signal, constant

α ₀₁And α ₀₂Be respectively the parameter of coil 1 and 2, α ₀₁Choose and make function

Maximization, α ₀₂Choose and make

Maximization.Wherein J ₁(x) be first kind first-order bessel function, h ₁₁And h ₁₂Be respectively the bottom of coil 1 and the height of distance from top liquid level, h ₂₁And h ₂₂Be respectively the bottom of coil 2 and the height of distance from top liquid level, r1 and r2 are respectively the radiuses of two coils;

(4) determine water level

(5) basis Formula is determined the conductivity.Here const1=Δ L ₀₁, μ ₀It is airborne magnetic permeability.

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