The runner blade clearance sensor measures distance variations between the turbine blade tip in relation to the throat ring surface. The surface of the turbine blade tip consists of NiCr conductive material absorbing high frequency Eddy currents generated by the measuring probe in order to provide an electrical signal proportional to the water gap. The probe itself is flush mounted on the throat ring at the turbine centre-line and measures static and dynamic distances in harsh hydraulic environments such as propeller or Kaplan turbines in large hydroelectric generators.