Measurement method of solution electric conductivity

Abstract

The method comprises: using a AC square wave current with a certain frequency (FH) to excite the electrode through a cable; making a synchronous detection for the response voltage waveform of the electrode to get a first mean voltage value; the first mean voltage value is divided by the current amplitude to get the resistance value (RH) of the first view; using a AC square wave current in another frequency (FL) to excite the electrode through a cable to make synchronous detection for the response voltage waveform to get a second mean voltage value; the second mean voltage value is divided by the current amplitude to get the resistance value (RL) of the second view; based on a mathematical model, getting the ratio relation of the inter-electrode resistance R to the RH, RL and FH, FL; based on it, getting the inter-electrode resistance value R; according to the electrode constant, getting the conductivity of the solution under test.

Description

technical field [0001] 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 [0002] 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 conductivity. However, the electrodes in the solution will be polarized after being energized, and U / I will change with time, so measurement errors will occur. The basic method to prevent measurement errors caused by polarization i...

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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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