What Are The Different Types Of Conductivity Meters?
There are two common types of conductivity meters, contacting and electrodeless.
Contacting Type
Insulated from each other, the contacting type usually consists of two electrodes, which are usually made from 316 stainless steel, titanium-palladium alloy or graphite. They are sized and spaced to provide a known cell constant.
A cell constant refers to a theoretical electrode of two one centimetre square plates 1 cm apart. A cell constant has units of 1/cm (per centimetre), where the number refers to the ratio of the distance between the electrode plates to the surface area of the plate.
Electrodeless Type
The electrodeless type induces an alternating current (AC) in a closed loop of solution and measures its magnitude to determine its conductivity.
Benchtop or Portable Meter
Although they both offer the same level of performance, there are some significant differences between a meter that is portable and one that is designed to live on a bench in a laboratory.
Portable meters are designed to be operated with one hand, are often shockproof and can withstand exposure to corrosive elements. However, there is a trade off, as there is limited navigation, reduced functionality and a smaller display screen.
Benchtop meters have larger screens, additional features with more buttons for calibration and browsing data.
Both portable and benchtop conductivity meters run routine measurements in applications such as water analysis, chromatography, or biological research.
If you are unsure, then please get in contact with our team who will happily talk through the various options with you.
How is conductivity measured?
Conductivity is measured with a probe and a meter. Voltage is applied between two electrodes on a probe immersed in the sample water. The drop in voltage caused by the resistance of the water is used to calculate the conductivity per centimetre.
The meter converts the probe measurements and displays the result on an LCD screen for the user to see and record.
What is it used for?
Conductivity is a measurement of dissolved solids, acids, bases and salts in a liquid solution. Electrical conductivity in a solution is a sign of impurity and that is why it is often used to measure the purity of water, as it is an efficient way of detecting contaminants.
It is also an effective tool for measuring the concentration of acids and bases through conduction.
Temperature Dependence
The conductivity of any solution is temperature dependent, so it is critical that you use a temperature compensated instrument or calibrate the meter at the same temperature as the solution being measured.
Which Industries Typically Use Them?
Conductivity meters are widely used in industries where water is critical for their business.
Waste Treatment and Industrial Applications
Water taken directly from a tap, lake or river is not necessarily suitable for industrial purposes as it contains unwanted contaminants. If those ionic contaminants are not removed they are likely to cause corrosion and scaling in industrial equipment like heat exchangers, boilers and refrigerators.
Using a conductivity meter is the ideal instrument for testing and monitoring the build up of dissolved ionic solids and is often used to ensure water is safe to drink. Conductivity measurements are critical in the desalination process as the removal of salts is critical for drinkable water and to prevent scale and corrosion throughout the industrial process.
Agriculture and Hydroponics
Monitoring nutrient solution concentrations in the hydroponics industry is critical as it is a process that grows plants without soil. Measuring the salinity of surface water is even more critical in agriculture, as water containing high salt levels encourages undesirable plant growth.
Therefore, the continual conductivity measurement of water in both these industries is crucial. Some prefer to use a conductivity meter rather than a salinity meter.
Aquaculture
In the aquaculture industry, the continual monitoring of salt concentrations within the water is vital as aquatic plants and fish have a limited range of salt tolerances. A conductivity meter, alongside TDS meters and oxygen meters, are a key component of water quality control.
Some businesses use a conductivity meter instead of a pH meter due to the strong relationship between pH and conductivity.
How to Choose The Right Meter?
The type of meter you require depends on the industry and what you need to measure.
For those in the food industry where the measurement of salt is critical, a toroidal conductivity meter should be used. It is an electrodeless sensor that removes any pollution and reduces long-term maintenance costs.
For small volumes, a microsensor would be recommended, especially if you are taking readings from a small glass or plastic bottle (vials). However, for larger volumes, a cell type conductivity meter would be suggested, allowing you to connect it to large tanks or pipes.
Cell types are often used by the chemical and pharmaceutical industries.
For industries that operate at high temperatures and solvents, a glass electrode conductivity meter is recommended as it can handle harsher conditions. They require handling and storing with extreme care as they are easy to break but they are easy to maintain.
Glass is used as high temperatures cause chemical reactions to plastic.
How Do You Calibrate A Conductivity Meter?
Calibrating a conductivity meter is essential as it will ensure the accuracy of the readings. The majority of manufacturers follow a similar standardised procedure.
Each meter has a menu item allowing you to put it into calibration mode. Using a buffer solution, which has a known and constant conductivity value at a set temperature value. By placing the probe/sensor into that solution, you can adjust the meter’s reading so it matches the solution.
Get In Touch
If you require any further information on conductivity meters, sensors or buffer solutions, please get in contact.
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