The eddy current method utilises high-frequency magnetic fields. The high-frequency magnetic field is generated by flowing a high-frequency current to the coil inside the sensor head. If a measurement target (metallic) is inserted into this magnetic field, electromagnetic induction causes magnetic flux to pass over the surface of the object and eddy currents to flow in the vertical direction. This causes the impedance of the sensor to change. Eddy current displacement sensors use the resulting change in oscillation to measure distance.