1. Knowledge Base
  2. Electrical Conductivity (EC)

Why do I need temperature compensation for measuring EC?

Conductivity changes with ion concentration and with temperature.

General Conductivity

When a solution is cooled, the ions do not have as much energy, so the conductance drops, and resistivity increases. For example, a standard potassium chloride solution used for the calibration of a cell constant and conductivity bridge, changes conductivity with the temperature. Having both the temperature and ion movement changing would make it near impossible to take useful conductivity measurements. If the temperature was held constant, the conductivity measurement would only have the variable of ion concentration. That is why temperature compensation with a temperature probe is important.

Absolute conductivity

Absolute conductivity is a conductivity measurement without temperature compensation. If the behavior of the conductivity change with the temperature change of a solution is known, the Conductivity measurements can be corrected to a reference temperature (typically 20 or 25°C) by carefully measuring the solution temperature. Fortunately, Hanna EC sensors incorporate an integral temperature sensor to measure solution temperature. Compensation corrects the measured conductivity to a reference temperature by applying a fixed factor β for linear compensation. High end meters allow adjustment of β to compensate for various solutions and permit the adjustment of a reference temperature over a wider range of temperatures. β for neutral salts is typically between 1.5 to 2.2%/°C.