The Differences Between Inductive and Contact Online Conductivity Meters

Inductive and Contact Online Conductivity Meters: Understanding the Differences

Conductivity meters are used in a variety of industries including pharmaceuticals, wastewater treatment, and chemical processing. These meters are used to measure the ability of a solution to conduct electrical current and therefore determine the concentration of dissolved substances in the solution. There are two common types of conductivity meters used; inductive and contact. Both methods have their advantages and limitations.

Inductive Conductivity Meters

Inductive conductivity meters are based on the principle of electromagnetic induction. A primary coil is used to create an alternating magnetic field, which induces an electrical current to flow in the solution being measured. The induced current causes a secondary magnetic field, which is detected by the meter's probes. The strength of the secondary magnetic field is proportional to the conductivity of the solution.

Advantages

Inductive conductivity meters are non-contact devices, which means that they do not have to be in contact with the solution being measured. This makes them ideal for situations where the solution is hazardous or where the solution cannot be easily accessed.

It is also easier to clean and maintain inductive conductivity meters since they do not come into contact with the solution being measured. This reduces the risk of contamination and ensures accurate readings over time.

Limitations

Inductive conductivity meters are not suitable for very low conductivity solutions since the induced current is too weak to generate a measurable magnetic field. Additionally, inductive conductivity meters are more sensitive to temperature changes than contact meters. Any change in temperature will affect the ability of the meter to induce an electrical current in the solution and consequently the accuracy of the readings will be affected.

Contact Conductivity Meters

Contact conductivity meters work by directly measuring the current flowing through the solution being measured. The probes of the meter are immersed in the solution and a small electrical current is passed through the solution. The strength of the current is measured by the meter, and the conductivity is calculated based on the measured current and the distance between the probes.

Advantages

Contact conductivity meters can be used to measure very low conductivity solutions. This is because the electrical current is passed directly through the solution, and there is no need for an induced current. Contact meters are also less sensitive to temperature changes since the electrical current is not affected by temperature.

Limitations

Contact conductivity meters are more prone to fouling since the probes are in contact with the solution being measured. This can lead to inaccurate readings over time. Additionally, contact conductivity meters cannot be used in hazardous environments or where the solution cannot be easily accessed.

Accuracy Comparison

Both inductive and contact conductivity meters have their advantages and limitations. In terms of accuracy, there is no clear winner since the accuracy of the readings depends on the specific application and the sensitivity of the meter being used.

However, in general, contact conductivity meters are considered to be more accurate at low conductivity levels since they are not affected by temperature changes and do not rely on an induced current. Inductive conductivity meters, on the other hand, are more suitable for high conductivity solutions and hazardous environments.

Conclusion

In conclusion, understanding the differences between inductive and contact conductivity meters is essential when selecting the right instrument for a specific application. Both types of meters have their advantages and limitations and should be selected based on factors such as the conductivity range of the solution, the environment in which the meter will be used, and the level of accuracy required. By being aware of these factors and applying them to instrument selection, accurate and reliable readings can be obtained consistently.