an inductive conductivity sensor is immersed in a liquid to measure its conductivity . the sensor comprises a transducer for generating a changing magnetic field and for inductively measuring an electric current induced in the liquid by the changing magnetic field . the transducer has an external surface facing the liquid . a elastic membrane separates the external surface from the liquid . the elastic membrane is periodically inflated and deflated to deform its outer shape and thereby remove deposits formed on the membrane .