The cell constant is the ratio of the distance between the electrodes to the area of the electrodes and it is generally specified for direct contact (galvanic) measurement. Most conductivity sensors on the market measure conductance, not specific conductivity and conductance x cell constant = conductivity. ifm does not specify a cell constant because the sensor design does not use two probe-type electrodes. The housing of the LDL100 forms one electrode and the sensor tip forms the other electrode. For more information, see technology.