The differential type level indicator cum controller is used for measurementof difference of two liquid levels. The level is detected by capacitanceprinciple. The capacitance is formed between the active electrode (flexibleTeflon taped wire) and the reference wire. As the liquid level rises(or falls)the capacitance between the active electrode and reference increases(ordecreases) which is converted into equivalent signal. The output of twoprobe unit is fed to the controllerunit to display the difference in leveland operate alarm output at anydesired differential level.