Electrical conductivity is a measure of a water sample’s ability to conduct electricity, and therefore a measure of the water’s ionic activity and content. In a water sample, the higher the concentration of ionic (dissolved) constituents, the higher the conductivity.
Conductivity is usually measured in units of micro Siemens per centimeter (µS/cm) or milliSiemens per centimeter (mS/cm). 1 mS/cm equals 1,000 µS/cm.
Conductivity of the same water changes substantially as its temperature changes. This can have a confounding effect on attempts to compare this feature across different waters, or seasonal changes in this parameter for a particular body of water. When measuring in specific conductance, the conductivity is normalized to temperature of 25°C. This eliminates complication, and allows valuable comparisons at different water temperatures.
Most conductivity meters display temperature, conductivity, and specific conductivity. They are usually calibrated in specific conductivity mode, which eliminates the need to enter values compensated for temperature.
Electrical Conductivity Compensation Chart
Below are three identical water samples from the same location on Pine Pond. They are each at a different temperature. Notice that the specific conductivity of each sample is the same, but the conductivity readings are significantly different.