About electric conductivity : Measurement systems

1. The two-electrode alternating current system

Two-electrode alternating current, four-electrode alternating current, and electromagnetic induction systems are currently in practical use. To measure electrical conductivity, immerse an electrical conductivity cell with a pair of energizing electrodes in the test solution and apply a current through the cell to measure resistance. Measurement is performed by alternating current, but when measured by direct current, a phenomenon called polarization occurs between the electrode surface and the liquid to be tested, and the true resistance of the liquid to be tested cannot be measured. The higher the electrical conductivity, the lower the polarization resistance due to the higher frequency alternating current, enabling highly accurate measurement. Our conductivity meters correspond to each other by switching frequencies.

2. Other systems

The AC four-electrode system has the advantages of being resistant to polarization and contamination, and is used for industrial applications. However, the structure and amplifier become complicated, making it difficult to reduce the size and cost.
The electromagnetic induction method measures electrical conductivity by electromagnetic induction. Although it is useful for areas with high electrical conductivity (such as seawater) because of its small effect of dirt and polarization, it is said to be unsuitable for small quantity measurement and measurement of low electrical conductivity because of its large electric conductivity cell.