Conductivity | Significance

What is conductivity?

Conductivity, also called conductivity, is a property of a liquid that says something about its ability to conduct electric current through it. It depends on the concentration of dissolved ions in the liquid. This is because these are the particles in the water that allow an electric current to pass through it.

In addition, conductivity is often a good property to determine the purity of a liquid. This is because pure water (or: demineralised water) contains very few ions, because the salts and minerals have been removed from it. As a result, the conductivity of pure water is often very low. On the other hand, you can also say that its resistance is therefore very high.

Conductivity | Measurement

The conductivity of liquids can thus be measured in the following ways:

  • Based on the number of particles (ions) in a liquid. Also called TDS or Total Dissolved Solids. The unit ppm is used for this. Also called Parts per Million.
  • Obv. the electrical conductivity. For this, the unit Siemens per centimetre or metre is used.

How do conductivity sensors work?

Conductivity measurement is often done with conductive or inductive sensors. Below you can find a small explanation of the various sensors available.

Conductive sensors

These sensors are characterised by 2 electrodes mounted opposite each other, where an electric current is conducted from one electrode to the other. The higher the electric current between these two electrodes, the higher the conductivity and the higher the number of Siemens per metre.

Conductive sensors are good for somewhat simpler conductivity measurements. They are less accurate than inductive sensors because disturbances in the measurement occur more easily, for example when there are heavy pumps in the system. In that case, an inductive conductivity sensor is usually chosen.

Conductive sensors with 4 electrodes

However, the above sensor with 2 electrodes is not always the right choice when determining the conductivity of a liquid. Especially in liquids with a high ion content, the polarisation effect can occur. Here, there are so many ions in a liquid that they can repel each other. This has a negative influence on current and can therefore affect the accuracy of the measurement.

Especially for this type of situation, there are also conductive electrodes with 4 electrodes. Unlike the "regular" conductivity sensor, this sensor consists of a "currentless" core with 2 additional electrodes. As a result, the sensor is not affected by the polarisation effect. The connected transmitter measures the potential difference between sensor and the currentless core and can thus calculate the conductivity.

Inductive sensors

This type of sensor contains two coils, a transmitting coil and a receiving coil, and an electrode that measures the current. An oscillator is used to create a magnetic field that causes a current to flow to the receiving coil. An overlying electrode is used to measure conductivity.

As indicated earlier, this measurement is more reliable when, for instance, there are heavy pumps in the system, such as in cooling water systems. However, an inductive conductivity sensor is a lot more expensive than a conductive sensor.

A water softener also uses the conductivity of water to make water "soft" again

Conductivity | Value Increase / Decrease

The purer the liquid, the poorer the conductivity. After all, low conductivity means that there are few (conductive) particles and impurities in the water. Lowering conductivity is often used in water treatment systems and within industry.

For such applications, an ion exchanger is often used. This is because this system can remove cations and anions from water. In short, it softens hard water. Colloquially, this is also known as a softener.

How does an ion exchanger work?

An ion exchanger consists of special beads that remove ions from the water. In water softeners, for example, lime and magnesium are removed from the water. This is done by passing the "hard" water through a cylinder of special synthetic resin beads. These synthetic resin beads are able to bind both lime ions and magnesium ions to themselves and exchange them with the sodium ions attached to the resin. In this way, the water is softened and conductivity can be reduced.

Conductivity | Applications

As described earlier, conductivity gives more insight into the purity of the water. Partly because of this property, measuring conductivity is interesting for industries that need to work with pure water or where hygiene plays a major role.

Industries or sectors using conductivity measurement are:

Water conductivity is monitored inline in cooling water systems

Conductivity | Metering Pumps and Systems

Within Emec's product range, we offer various solutions for measuring and controlling the conductivity of liquids. From sensors to controllers, which allow you to record measurements and control dosing systems if required. You have also come to the right place for complete systems for treating cooling water. 

Sensors suitable for measuring conductivity 

At Dosing Pump Shop, we offer a wide range of sensors for measuring conductivity. From the more simple conductivity meter ECDC by ECDIND high precision inductive conductivity sensor.

Controllers to monitor conductivity

Emec offers a number of controllers that can read the above sensors and control dosing systems and pumps on them. The Emec MTower and CENTURIO are mainly designed for treating cooling water. These controllers have the function to measure conductivity and additional parameters as standard. For more information on these solutions and an overview of the additional parameters, please visit the product page.

About Emec Metering Pumps

Emec is an Italian company that has specialised in dosing systems and measuring equipment for chemicals for over 35 years. This extensive experience and passion for the product is reflected not only in the reliability and innovation of the dosing systems, but also in customer focus. For example, Emec offers a 5-year warranty* (!) as well as excellent after-sale support.

* Warranty applies to the equipment and diaphragm only. Not for the wet parts such as the pump head.

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