Conductivity reveals a lot about the degree of purity of a body of water - provided that temperature and substance are correctly taken into account. We show how conductivity can be reliably measured and evaluated - including temperature compensation.
Conductivity is a key measured value in the analysis of water and other liquids. However, depending on the substance and area of application, different aspects need to be taken into account - above all temperature as the biggest influencing factor.
Conductivity is expressed in microsiemens per centimeter(µS/cm) and describes the ability of a liquid to conduct electricity. The conductance is the reciprocal of the electrical resistance. This means that the higher the conductivity, the lower the resistance - and the more dissolved ions there are in the liquid.
Pure water has a very low conductivity of only around 0.055 µS/cm. Water only becomes conductive through dissolved substances such as chlorides, sulphates or mineral salts - to around 500 µS/cm for drinking water. Increased conductivity can indicate contamination and is therefore an important environmental indicator.
Typical areas of application:
Please note: Conductivity only provides an initial indication. For a precise analysis, additional chemical tests are necessary - for example for hormones or pesticides, which do not form ions and are therefore not conductive.
Another area of application is hydraulic analysis: the conductivity can be artificially increased by adding salt at a specific point. Point measurements along the river or canal then allow conclusions to be drawn about the direction and speed of flow.
Conductivity is strongly dependent on temperature. Two samples of the same liquid can show different conductivity values at different temperatures - without their chemical composition having changed. Temperature compensation is therefore essential for comparable results.
The solution: Modern sensors measure conductivity and temperature simultaneously. Temperature compensation converts the measured conductivity value to a uniform reference temperature - usually 25 °C.
That depends on the substance being analyzed:
The formula for calculating the percentage temperature dependence is
α = (ΔK(T)/ΔT) / K(25°C) * 100Example calculation: Determination of the temperature dependency for a rapid descaler:
Calculation:
ΔK = 135.20 - 122.37 = 12.83 mS/cm ΔT = 26 - 20 = 6 °C K(25 °C) = 133.10 mS/cm α = (12.83 / 6) / 133.10 * 100 ≈ 1.60 %/°CConductivity measurement is a simple and effective method for analyzing liquids - provided that the temperature and medium are taken into account correctly. Whether in environmental technology, water analysis or industry: modern sensor solutions with integrated temperature compensation provide reliable values and therefore enable safe decisions to be made.