Causes and Solutions for Unstable Conductivity Readings in Reverse Osmosis Water Treatment

• Why is it difficult to measure the conductivity of reverse osmosis water?
  • Carbon Dioxide Absorption from the Air
  • Limited precision and automatic range adjustment of the meter
  • The conductivity electrode used is not specifically designed for pure water
  • During the measurement process, tiny bubbles may be generated near the conductivity electrode measuring element, which can also interfere with the measurement.
• How to measure conductivity efficiently and accurately in reverse osmosis Plants?
  • Choosing the right portable conductivity meter and conductivity probe
  • Other practical Tips for Reliable Conductivity Measurement

Measuring the electrical conductivity of water is crucial in industry and laboratories, especially when dealing with reverse osmosis water. However, many technicians often face unstable readings or slow increases when using standard portable conductivity meters. Unlike regular water samples, the ion concentration in reverse osmosis water is low, making it difficult to obtain accurate readings quickly.

Measuring the electrical conductivity of water is of vital importance in industry and laboratories, especially when dealing with reverse osmosis water. However, many technicians often encounter problems such as unstable readings or slow growth when using standard portable conductivity meters. Unlike conventional water samples, the ion concentration in reverse osmosis water is very low, making it difficult to obtain accurate readings quickly.

Why is it difficult to measure the conductivity of reverse osmosis water?

Due to the high purity of reverse osmosis water, its electrical conductivity is usually below 10 microsiemens per centimeter. This means that even the slightest interference can significantly affect the measurement results. The following are some reasons why the conductivity of reverse osmosis water is difficult to measure.

1. Carbon Dioxide Absorption from the Air

One of the main reasons for the fluctuation in the conductivity reading of reverse osmosis water is that RO water has almost no buffering capacity and is prone to absorbing CO₂ to form carbonic acid, which increases conductivity. When the sample water is exposed to the air, it will gradually absorb CO₂, causing the reading to continuously rise until it stabilizes. It’s easily notice when using a portable conductivity meter in environments with high carbon dioxide concentrations.

2. Limited precision and automatic range adjustment of the meter

Many conductivity meters are built with an automatic range adjustment function, which can adjust the range according to the measured conductivity. At extremely low conductivity levels (such as reverse osmosis water), the sensitivity of the meter itself may be affected, resulting in readings with large errors.

3. The conductivity electrode used is not specifically designed for pure water

Standard conductivity meters typically come with a conductivity electrode with a constant of 1. When measuring low conductivity water samples (such as ultrapure water, distilled water, RO water), the electrode is prone to polarization or, due to its structural characteristics, it is easy to adsorb impurity ions from other samples, leading to increased errors.

4. During the measurement process, tiny bubbles may be generated near the conductivity electrode measuring element, which can also interfere with the measurement.

How to measure conductivity efficiently and accurately in reverse osmosis Plants?

Choosing the right portable conductivity meter and conductivity probe are crucial for accurately managing the water quality in reverse osmosis plants. The following is the most reliable combination for measuring the conductivity of RO water.

Lab-Grade Portable Conductivity TDS Resistivity Salinity Meter with High-Accuracy L111C06

L111C06 digital EC meter is a high-precision conductivity meter for water, supporting conductivity(EC) , total dissolved solid(TDS), salinity, and electrical resistivity measurement. The built-in nonlinear temperature compensation function, ensures highly accurate and reliable results in ultra-pure water. The L111C06 digital conductivity meter is designed for professional users requiring advanced features like GLP compliant data storage, USB data export and monitoring. The Foldable stand converts the handheld EC meter into a benchtop EC meter for laboratory testing. With a rugged IP57 rated design, large backlit display, adjustable TDS factor and reference temperature factor, as well as a comprehensive test kit, the L111C06 digital conductivity meter meets the testing demands of laboratory, field, or industrial applications.

Precision Glass Conductivity Electrode K=0.1 for Pure Water LS911C

The LS911C glass conductivity sensor is designed for precise analysis of pure water conductivity. With a chemically stable glass housing and a low cell constant (0.1±0.2 cm⁻¹), the LS911C glass conductivity sensor performs well in measuring conductivity below 10 μS/cm, providing high accuracy for applications in the power and semiconductor industries. When equipped with an optional glass flow cell, the interference from CO₂ in the environment can be eliminated effectively, further improving measurement accuracy. Its standard BNC connector allows for easy connection to a variety of conductivity measurement systems.

Other practical Tips for Reliable Conductivity Measurement

• Minimize air exposure, measure the sample immediately after collection or isolate it using a closed sampling system (such as an optional glass flow cell equipped to conductivity sensor LS911C).
• Periodic Calibration, calibrate the conductivity meter using a low-conductivity calibration solution.
• Make sure that the electrode constant between the portable conductivity meter and the conductivity meter is matched.
• Before testing, rinse the conductivity electrode repeatedly with pure water.
• During the test, check whether there are bubbles near the electrode sensitive elements. If so, remove the bubbles.

To accurately measure the conductivity of reverse osmosis water, it is essential to understand the unique properties of ultrapure water. Using dedicated portable conductivity meters (such as the L111C06) can significantly reduce common measurement challenges and ensure reliable and stable measurement results, which is critical for industrial, laboratory, and reverse osmosis plant applications.