Are the test values of a conductivity meter affected by water flow?

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Does the flow rate of water affect the readings of conductivity or resistivity values? The value of conductivity or resistivity depends on the purity or composition of the water, and is essentially independent of the flow rate through the sensor. However, several minor factors can still affect the measurements, especially those of high-purity water. Low flow rate: Trace impurities on the surface of new pipelines or those that have just been replaced can dissolve in water; at low flow rates, these impurities may settle and reduce the resistivity, especially in some dead corners. Bubbles formed on the sensor surface due to any significant leakage can cause unstable and high resistance readings. If the flow rate is too low, bubbles will adhere to the surface of the sensor, thereby changing the electrode constants; the sensor should be installed in such a way that the bubbles rise and detach from it. When air dissolved at lower water temperatures enters a treatment system with lower pressure and higher temperature, its solubility decreases, which may result in the formation of bubbles inside the sensor and cause the phenomena described above. After cation exchange treatment, carbon dioxide is released, resulting in the same phenomenon. If trace amounts of air leak in, it still contains a certain amount of carbon dioxide, even if no bubbles are formed, which will reduce the resistivity of the ultrapure water. Changes in flow rate may reduce or dilute the leaking air, resulting in significant sensitivity to flow rate. When measuring conductivity/resistivity in the bypass or sample line, low flow rates can cause delays in the actual process. The same problem applies in the case of air leaks. High flow rate: A high flow rate is actually better for measurement, but an excessively high flow rate can exert a pressure on the conductivity electrodes, resulting in the \"cavitation effect\" – bubbles of water vapor formed due to partial vacuum. It not only causes significant variations in readings but also damages the sensor. Our experience shows that flow rates between 0.3 and 3 m/s (1–10 feet per second) help to obtain accurate measurement results. However, these factors should be taken into consideration in practical applications.