Solution conductivity measuring method

Abstract

The invention discloses a solution conductivity measuring method. The measuring system comprises a dipolar or quadrupolar electrode, a measuring instrument and connecting cable. The method comprises the following steps: exciting the electrode by the AC square wave current with a fixed current amplitude and a fixed frequency by the cable; performing high speed A / D conversion to the voltage waveform in response to the electrode, and obtaining voltage values of three different time, or three voltage mean values of three different time sections on the waveform; setting an equation according to the known electrode response voltage waveform function V=R*IH[B<2>(1-(2 / (1+D)D<t / TH>)+B(1-B)1n(D)(1 / 2-t / TH)], and calculating out three independent parameters R, B, D, wherein, the R is resistance value between the electrodes to be measured, B=CP / (Cs+CP), D=e<-TH / T>, T=(CsCP / (Cs+CP))R, Cp represents equivalent capacitance of electrode polarization, Cs represents the sum of the cable equivalent capacitance, the capacitance of the measuring instrument input circuit and the electrode distribution capacitance, and the TH represents the half period of the AC square wave current, IH represents the current amplitude of the AC square wave current; and obtaining the conductivity value of the solution to be measured according to R combining the electrode constant.

Description

[0001] This application is a divisional application of a Chinese patent application with application number 200610030555.6 and a filing date of August 30, 2006 entitled "Method for Measuring the Conductivity of a Solution" technical field [0002] The invention relates to a method for measuring the conductivity or resistivity of a solution, in particular to a method for measuring the conductivity or resistivity of a solution capable of eliminating the effects of electrode polarization and long cables. Background technique [0003] The basic measurement method of the conductivity of the solution is to put the electrode into the solution, energize the solution through the electrode, measure the voltage U at both ends of the electrode and the current I flowing through, and calculate the resistance between the electrodes R=U / I, using the formula G=C / R to calculate the conductivity of the solution, where C is the cell constant and the resistivity is the reciprocal of the conducti...

AI Technical Summary

Problems solved by technology

However, the frequency should not be too low, otherwise, due to polarization, the AC square wave current excitation method will cause saturation of the excitation circuit or input operational amplifier circuit, causing measurement errors

Since in the actual measurement, the equivalent capacitance of the cable and the electrode polarization always exist at the same time, so no matter what frequency is used for measurement, there will always be errors in the usual method.

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