Eddy Current Sensor Probe : Eddy currents are formed when a moving (or changing) magnetic field intersects a conductor, or vice-versa.
The relative motion causes a circulating flow of electrons, or currents, within the conductor. These circulating eddies of current create electromagnets with magnetic fields that oppose the effect of the applied magnetic field.
The stronger the applied magnetic field, or greater the electrical conductivity of the conductor, or greater the relative velocity of motion, the greater the currents developed and the greater the opposing field Eddy current probes sense this formation of secondary fields to find out the distance between the probe and the target material.
Capacitance Proximity Sensors : Capacitive sensors use the electrical property of “capacitance” to make measurements.
Capacitance is a property that exists between any two conductive surfaces within some reasonable proximity. Changes in the distance between the surfaces change the capacitance. It is this change of capacitance that capacitive sensors use to indicate changes in position of a target.
High-performance displacement sensors use small sensing surfaces and as result are positioned close to the targets .