cellkonstant

Cell constant, sometimes referred to as Zellkonstante in German literature, is a geometry-based factor used in electrochemical conductivity measurements to relate the conductance of a solution as measured by a cell to the solution’s electrical conductivity. It depends on the physical dimensions of the cell, notably the distance between the electrodes and their surface area.

For a conductivity cell with two electrodes, the cell constant K is defined by K = l/A, where l is the distance between electrodes and A is the electrode area. The unit is typically cm^-1. The sample conductivity κ (S/cm) is obtained from the measured conductance G (S) by the relation κ = G × K. Equivalently, G = κ / K. Thus, accurate knowledge of K is essential to convert measured conductance into true conductivity.

Calibration of the cell constant is commonly done with standard solutions of known conductivity, κ_s, yielding K = κ_s / G_s at a chosen temperature. Temperature affects the solution’s conductivity and instruments usually specify a reference temperature (often 20–25°C) with temperature compensation applied for κ.

Cell geometry variations include parallel-plate, concentric cylindrical, and other configurations; the geometry determines K and, consequently, the sensitivity and measurement range of the cell. A smaller K (larger electrode area or shorter gap) increases conductance for a given κ.

Practical considerations include the influence of electrode cleanliness, polarization, and fouling on G, which can affect accuracy. Regular calibration with standards is recommended, particularly for precise measurements or measurements across varying temperatures.

Applications are widespread in water quality testing, chemical analysis, and industrial process control.