WO2007107108A1 - Procédé permettant de mesurer la conductivité d'une solution et dispositif correspondant - Google Patents

Procédé permettant de mesurer la conductivité d'une solution et dispositif correspondant Download PDF

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Publication number
WO2007107108A1
WO2007107108A1 PCT/CN2007/000890 CN2007000890W WO2007107108A1 WO 2007107108 A1 WO2007107108 A1 WO 2007107108A1 CN 2007000890 W CN2007000890 W CN 2007000890W WO 2007107108 A1 WO2007107108 A1 WO 2007107108A1
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WIPO (PCT)
Prior art keywords
conductivity
measuring
value
cell
measurement
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Application number
PCT/CN2007/000890
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English (en)
Chinese (zh)
Inventor
Weizhong Huang
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Weizhong Huang
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Publication date
Application filed by Weizhong Huang filed Critical Weizhong Huang
Publication of WO2007107108A1 publication Critical patent/WO2007107108A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/06—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a liquid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/22—Measuring resistance of fluids

Definitions

  • the invention relates to the field of electrochemical measurement technology, in particular to a method and a device for measuring the conductivity (resistivity) of a solution. Background technique
  • g is the conductivity, unit: S/cm
  • R is the resistivity, unit: Q/cm.
  • the measurement of conductivity can be converted into a measure of resistivity.
  • the measurement method of conductivity mainly includes AC conductance measurement method (DC conductance measurement method is rarely used because it is difficult to solve the "polarization effect problem" of the electrode).
  • the AC conductance measurement method is to add an AC signal between the two poles of the conductivity cell, and use the AC signal to reduce the influence of the polarization effect.
  • one electrode of the conductivity cell 1 is connected to the opposite end of the operational amplifier A, and a feedback resistor Rf is connected between the opposite end and the output end of the operational amplifier A.
  • the forward end of the amplifier A is grounded, and an AC square wave signal Vi with a stable amplitude and a half cycle pulse width T is applied to the conductivity cell 1, and the output voltage Vo of the operational amplifier A is measured, and then obtained by the following formula (2) Conductivity.
  • Vo(t) is the output of the op amp
  • Vi(t) is the input AC square wave voltage signal
  • R is the resistance of the solution in the conductivity cell
  • Rf is the feedback resistor value of the op amp.
  • Ve(t) is the influence of the polarization layer (polarization potential) on the conductance electrode in the conductance measurement
  • Vc(t) is the influence of the capacitance on the conductance electrode in the conductance measurement.
  • the conventional method can only be applied to a limited measurement range. Once the measurement range is exceeded, the calculated resistance of the solution in the conductivity cell will be far from the actual value. And as the degree of polarization increases, this conventional approach will ultimately not be applicable to the actual operation at all.
  • the main measurement error is caused by the capacitance effect between the two poles and the two poles, and the measurement of high conductivity value, the main measurement error is Caused by the polarization layer (polarization potential) generated on the conductivity electrode, and the following methods are taken to reduce the measurement error:
  • Method 2 In the measurement of low conductivity value, by reducing the frequency of the AC signal applied to the conductivity electrode, the measurement error caused by the capacitance effect on the conductivity electrode is weakened, thereby improving the measurement accuracy. However, reducing the frequency of the alternating current signal applied to the conducting electrode is also limited, otherwise the polarization layer effect actually present on the conducting electrode affects the measurement accuracy.
  • Method 3 Under the same cell constant, by increasing the electrode surface area of the conducting electrode (such as plating platinum black on the bright platinum electrode), reduce the current density on the surface of the electrode of the conducting electrode, thereby correspondingly reducing the high conductivity value.
  • the measurement error caused by the polarization layer (polarization potential) generated on the conductivity electrode during measurement increases the measurement range.
  • the electrode surface area of the platinized black conductivity electrode is poor in physical stability. Conductance If the platinum black on the electrode surface is peeled off, the conductivity of the conductivity electrode will change, which directly affects the measurement accuracy and is not easy to detect during use.
  • a method for measuring the conductivity of a solution comprising the steps of: applying a half-cycle AC signal source having a pulse width T to the two poles of the conductivity cell; measuring at a Txl in the range of 0-49% T in either half cycle a first voltage value XI of the conductivity cell; measuring a second voltage value ⁇ 2 of the conductivity cell at a certain ⁇ 2 in the range of 51-100% T in any one half cycle; and using the measured first voltage value and second voltage The value calculates the conductivity.
  • the AC signal source used is a square wave AC source.
  • a voltage value XI and the second voltage value ⁇ 2 of the conductance cell is measured at a Tx2 in the range of 0-49% T before the rising edge of the upper half cycle or the rising edge of the lower half cycle.
  • the measuring method of the present invention further includes the following steps: when the value of X1/X2 is greater than a predetermined upper limit value or the value of X2/X1 is less than a predetermined lower limit value, a measurement alarm is proposed, It is also required to replace the conductivity cell with a larger cell constant for measurement.
  • a measuring device for measuring the conductivity of a solution comprising: a signal applying device for applying a half-cycle alternating current signal source having a pulse width of ⁇ to the two poles of the conductivity cell; and measuring means for using in any half cycle 0- Measuring the first voltage value XI of the conductivity cell at a certain Tx1 in the range of 49% ⁇ , and in any half cycle Measuring a second voltage value X2 of the conductivity cell at a certain Tx2 in the range of 51-100%T; and calculating means for calculating the conductivity using the measured first voltage value and second voltage value.
  • the AC signal source used is a square wave AC source.
  • the measuring device measures the first voltage value XI of the conductance cell at a certain Tx1 in the range of 0-49% ⁇ in the rising edge of the upper half or the falling edge of the lower half cycle, and in the upper half of the circumference Measuring the second voltage value of the conductivity cell at a certain Tx2 in the range of 0-49% T before the falling edge or the rising edge of the lower half cycle
  • the measuring device further comprises a measuring alarm device for proposing when the value of X1/X2 is greater than a predetermined upper limit value or the value of X2/X1 is less than a predetermined lower limit value The alarm is measured and a larger conductivity cell constant conductivity electrode is required for measurement.
  • the present invention can theoretically completely eliminate the capacitance effect of the conductivity cell (Vc(t) in equation (3)) and the pole as long as the two output voltage values are measured within a specific range.
  • the measuring method and device according to the present invention can theoretically completely eliminate the influence of the capacitance effect and the polarization effect of the conductivity cell on the measurement, even if some errors in the actual measurement are considered, compared with the prior art,
  • the capacitance effect of the conductivity cell and the influence of the polarization effect on the measurement are reduced, thereby significantly expanding the measurement range of the conductivity cell.
  • the measurement range of the same conductivity electrode can be expanded by an order of magnitude in both the low range and the high range.
  • a conductivity electrode with a cell constant of 0.01 can be calibrated in a 146.6 uS/cm standard conductivity solution.
  • a conductivity electrode with a constant conductivity cell of 0.1 can be calibrated and verified in a standard conductivity solution of 146.6 uS/cm and 1413 uS/cm.
  • the measurement range from O.OluS/cm to 30 m S/cm basically covers the commonly used measurement range.
  • the same conductivity constant of the platinum cell conductance electrode has the same measurement range as the platinum-plated conductivity electrode of the conventional measurement method, but the cell constant stability of the bright platinum conductivity electrode and the use of the electrode The lifetime is much larger than the platinum-plated conductivity electrode, which undoubtedly provides the tester with another better choice.
  • the measurement method and apparatus of the present invention also extends the measurement range of the platinum-plated conductivity electrode by an order of magnitude.
  • the measuring method and apparatus of the present invention greatly reduce the influence of the capacitance effect and the polarization effect of the conductivity cell on the measurement, the measuring range of the conductivity cell is expanded in actual operation compared with the conventional prior art. Therefore, the conventional conductivity electrode which cannot be directly determined by the direct calibration method can be directly calibrated by the method and apparatus of the present invention; previously, only one solution can be used to directly calibrate the conductivity cell constant. Now, with the measuring method and device of the present invention, not only the cell constant can be directly calibrated, Another standard conductivity solution can also be used to verify the accuracy of the measurement.
  • the measuring method and apparatus of the present invention can determine the degree of polarization of the conducting electrode, when the polarization effect is large and has an influence on the measurement, the user can be warned that the larger conductivity cell should be replaced. Constant conductivity electrodes are reliably measured to avoid erroneous measurements.
  • the measurement of the acid-base concentration of a single component by the measuring method and apparatus of the present invention can achieve a higher measurement accuracy than the method of measuring the acid-base concentration of the electromagnetic method.
  • the influence of the distributed capacitance of the conductive electrode cable on the measurement can be reduced.
  • Figure 1 is a basic circuit diagram of conductivity measurement.
  • Fig. 2a is a waveform diagram of a square wave AC source input according to the first embodiment of the present invention.
  • Figure 2b is a waveform diagram of the output voltage of the conductivity cell in a non-polarized state according to the first embodiment of the present invention.
  • Fig. 2c is a waveform diagram of the output voltage of the conductivity cell when there is polarization influence according to the first embodiment of the present invention.
  • Figure 2d is a waveform diagram of the output voltage of the conductivity cell in a severely polarized state according to the first embodiment of the present invention.
  • Fig. 3 is a basic circuit diagram of resistivity measurement according to a second embodiment of the present invention.
  • Figure 4a is a waveform diagram of a square wave AC source input according to a second embodiment of the present invention.
  • FIG. 4b is a waveform diagram of an output voltage of a conductivity cell in a non-polarized state according to a second embodiment of the present invention.
  • Figure 4c is a waveform diagram of the output voltage of the conductivity cell when polarized according to the second embodiment of the present invention.
  • Figure 4d is a waveform diagram of the output voltage of the conductivity cell in a severely polarized state according to the second embodiment of the present invention.
  • Figure 5 is a flow chart of a measurement method in accordance with the present invention. BEST MODE FOR CARRYING OUT THE INVENTION The method and apparatus for measuring the conductivity of a solution of the present invention will be further described below in connection with several specific embodiments.
  • the electrical conductivity to which the present invention is applicable is the most readily available two-pole conductivity electrode on the market, and the same applies to Embodiment 1 and Embodiment 2.
  • Example 1 The electrical conductivity to which the present invention is applicable is the most readily available two-pole conductivity electrode on the market, and the same applies to Embodiment 1 and Embodiment 2.
  • Example 1 The electrical conductivity to which the present invention is applicable is the most readily available two-pole conductivity electrode on the market, and the same applies to Embodiment 1 and Embodiment 2.
  • the conductivity measurement circuit used is basically the same as the conventional conventional measurement circuit.
  • One electrode of the conductivity cell 1 is connected to the opposite end of the operational amplifier A, and between the opposite end and the output end of the operational amplifier A. Connected to the feedback resistor Rf, the forward terminal is grounded.
  • an alternating square wave signal Vi having a stable amplitude and a half cycle pulse width T is applied to the conductivity cell 1; then, 0-49% T in any half cycle.
  • the output voltage XI of the operational amplifier A is measured at a certain Txl in the range; the output voltage X2 of the operational amplifier ⁇ is measured again at a certain ⁇ 2 in the range of 51-100%T in any half cycle; the measured two voltage values XI and X2 are
  • the following formula (3) is combined to obtain the resistance value R of the solution in the conductivity cell, and the conductivity g of the solution in the conductivity cell is obtained by the formula (1).
  • Vo(t) is the output of the op amp
  • Vi(t) is the input AC square wave voltage signal
  • R is the resistance of the solution in the conductivity cell
  • Rf is the feedback resistance of the op amp
  • Ve (t) is the amount of influence of the polarization layer (polarization potential) on the conductance electrode in the conductance measurement
  • Vc(t) is the influence amount of the capacitance on the conductance electrode in the conductance measurement.
  • K is the cell constant (also known as the cell constant)
  • g is the conductivity
  • the unit is: S/cm
  • R is the resistivity, in units of Q/cm.
  • the current signal of the conductivity cell 1 is measured at a Txl value within a range of 0-49% T from the rising edge of one half cycle.
  • XI, and the value X2 at a certain Tx2 in the 0-49% T range before the falling edge of this half-cycle.
  • the value XI and the value X2 may not be measured in the same half cycle, which does not affect the accuracy of the measurement of the present invention.
  • monitoring of the polarization state can also be derived by the present invention. Specifically, a certain upper limit value or a lower limit value indicating that the polarization phenomenon is very serious is preset, and when the value of X1/X2 is greater than the upper limit value or less than the lower limit value, a measurement alarm is proposed, and the replacement is required to be larger.
  • the conductance electrode of the cell constant is reliably measured to avoid measurement operations with large measurement errors.
  • the measurement circuit used is different from that of Embodiment 1 in that the feedback resistance is interchanged with the position of the conductivity cell.
  • the two electrodes of the conductivity cell 1 are connected between the inverting end and the output end of the operational amplifier A, and the operation is placed
  • the reverse terminal of the amplifier A is connected to a feedback resistor Rf.
  • the forward side of operational amplifier A is grounded.
  • an AC square wave signal Vi having a stable amplitude and a half cycle pulse width T is applied to the cell 1; then, the operational amplifier A is measured at a Tx1 in the range of 0-49 ⁇ 3 ⁇ 4T in either half cycle.
  • the output voltage XI; the output voltage X2 of the operational amplifier ⁇ is again measured at a certain ⁇ 2 in the range of 51-100%T in any half cycle; the measured two voltage values XI and X2 are combined with the following formula (3) to obtain
  • the resistance value R of the solution in the conductivity cell is obtained by using the formula (1) to obtain the conductivity g of the solution in the conductivity cell.
  • Vo(t) is the output of the op amp
  • Vi(t) is the input AC square wave voltage signal
  • R is the resistance of the solution in the conductivity cell
  • Rf is the feedback resistance of the op amp
  • Ve (t) is the amount of influence of the polarization layer (polarization potential) on the conductance electrode in the conductance measurement
  • Vc(t) is the influence amount of the capacitance on the conductance electrode in the conductance measurement.
  • K is the cell constant (also known as the cell constant)
  • g is the conductivity
  • the unit is: S / C m
  • R is the resistivity
  • unit Q / cm.
  • the current signal of the measuring cell 1 is measured within a range of 0-49% T at the rising edge of one half cycle.
  • the value XI and the value X2 may not be measured in the same half cycle, which does not affect the accuracy of the measurement of the present invention.
  • the waveform of the output voltage Vo of the operational amplifier A is substantially the same as the waveform of the input alternating current square wave signal Vi.
  • the waveform of the output voltage Vo of the operational amplifier A is greatly deformed, especially in the case of severe polarization. in the case of. This is very detrimental to existing measurement methods and can result in inaccurate measurements.
  • the value XI and the value X2 measured according to the method of the present invention are always accurate no matter what polarization state occurs.
  • the polarization state can also be monitored.
  • the specific process is exactly the same as that in Embodiment 1, and will not be repeated here.

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Abstract

Cette invention concerne un procédé consistant à mesurer la conductivité d'une solution ainsi qu'un dispositif correspondant. Le procédé consiste à appliquer une source de signaux CA présentant une largeur d'impulsion de demi-période T; à mesurer la première valeur de tension X1 de la cellule de conductivité à Tx1 dans n'importe quelle demi-période T comprise entre 0 et 49% et la seconde valeur de tension X2 de la cellule de conductivité à Tx2 dans n'importe quelle demi-période comprise entre 51 et 100%. Lorsque la valeur X1/X2 est supérieure à la valeur limite supérieure prédéterminée ou lorsque la valeur X2/X1 est inférieure à la valeur limite inférieure prédéterminée, le dispositif déclenche des alarmes de mesure afin de solliciter le changement des pôles de conduction d'une cellule de conductivité encore plus grande pour permettre des mesures fiables. La première tension X1 et la seconde tension X2 sont utilisées pour calculer la conductivité.
PCT/CN2007/000890 2006-03-22 2007-03-19 Procédé permettant de mesurer la conductivité d'une solution et dispositif correspondant WO2007107108A1 (fr)

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CN200610024967.9 2006-03-22

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2369330A1 (fr) * 2010-03-10 2011-09-28 DBK David + Baader GmbH Dispositif de mesure destiné à la détection de la conductivité d'un liquide
WO2014105501A1 (fr) * 2012-12-27 2014-07-03 General Electric Company Mesures de conductivité à dynamique étendue dans l'eau
CN108919165A (zh) * 2018-06-29 2018-11-30 中国大唐集团科学技术研究院有限公司华中分公司 一种便携式在线电导率表电极常数检验装置及检验方法

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CN1821763A (zh) * 2006-03-22 2006-08-23 黄伟忠 一种溶液电导率的测量方法
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CN105092979B (zh) * 2014-05-23 2018-02-27 中国海洋大学 一种海洋用Ag/AgCl电场传感器内阻测量方法
CN105588983B (zh) * 2014-11-14 2021-04-23 佛山市顺德区美的电热电器制造有限公司 电导率的测试装置和用电设备
CN104459334B (zh) * 2014-12-26 2017-08-25 福建师范大学 使液体循环流动冲刷电极表面的直流激励电导率测量方法
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JP7132015B2 (ja) * 2018-07-24 2022-09-06 アズビル株式会社 電気伝導率計
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CN109142463A (zh) * 2018-10-09 2019-01-04 李晨天 暂态直流电导测量方法及装置
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Cited By (6)

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Publication number Priority date Publication date Assignee Title
EP2369330A1 (fr) * 2010-03-10 2011-09-28 DBK David + Baader GmbH Dispositif de mesure destiné à la détection de la conductivité d'un liquide
WO2014105501A1 (fr) * 2012-12-27 2014-07-03 General Electric Company Mesures de conductivité à dynamique étendue dans l'eau
US9116099B2 (en) 2012-12-27 2015-08-25 General Electric Company Wide dynamic range conductivity measurements in water
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CN108919165A (zh) * 2018-06-29 2018-11-30 中国大唐集团科学技术研究院有限公司华中分公司 一种便携式在线电导率表电极常数检验装置及检验方法

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