High frequency technology offers an extremely accurate distance measuring proximity sensor principle. In the close nearfield the resolution is better than 200 nanometer. The function is based on the shift of the resonance frequency of a cylindrical ceramic resonator by approaching conductive targets. Shown in the top photo is the electric field strength (red high, blue low) inside and outside the ceramic resonator. If a target enters the outside electromagnetic field of the sensor, the resonance frequency is shifted. The absolute value of the frequency shift determines the distance to the target.Photo of the sensor and simulation of the electric field strength within the sensor detection range