STELZNER® agricultural measurement systems

Measuring conductivity in a solution

Electrical conductivity determines the electrical current between two points (electrodes) of different voltage potentials in a liquid. The conductivity increases as the amount of salt, acid or base contained in a solution increases. Conductivity is measured in units of mS/cm. The scale for water-based solutions starts with pure water (conductivity equals 0.05 µS/cm at 25 °C) and ends with a basic solution of 1.0 mS/cm (e.g., potassium solutions). Potable or surface water has a conductivity value in a range from 0.1 to 1.0 mS/cm. Conductivity is measured using a measuring cell which consists (in the simplest case) of two similar electrodes. An AC voltage is applied to an electrode and this causes the ions in the solution to move in relation to the electrode. More current flows between the electrodes when more ions are contained in the solution. Using this measured current, the meter calculates the conductance of the solution and then, based on the cell specification, the actual conductivity value. Areas of applications: For horticulture, the conductivity value is also referred to as the EC value. The EC value is an indicator for the quantity of dissolved salts. It is specified in mS/cm. The EC 2000 is used in all areas of cultivation and irrigation systems, including classic floriculture, substrata production and soil-free cultivation. It enables you to monitor basis solutions and nutrient solutions during fertilization. You can also check the salt content in substrata mixtures. Please note: For the basis and nutrient salt solutions with high salt content, we recommend using the glass-platinum conductivity electrode instead of the carbon conductivity electrode. In solutions with high salt concentrations, the glass-platinum conductivity electrode has less polarization and thus provides improved linearity and more accurate readings. The EC 2000 is a precise measuring instrument with temperature compensation that can be calibrated. It is used for quickly determining the mS/ EC values in solutions from 0 – 20 mS/cm (with a carbon conductivity electrode) or 0 – 200 mS/cm (using a glass-platinum conductivity electrode).