The conductivity sensor is a two-pole cell whose resistance varies in function of the conductivity of the liquid it is immersed in. That conductivity will be proportional to the conductance of the sensor (the inverse of its resistance), multiplied by the constant cell, in the case of the Libelium sensor around 1 cm-1, leading to a value in Siemens per centimeter (S/cm). To power the conductivity sensor an alternating current circuit has been installed in order to avoid the polarization of the platinum electrodes.
