The working principle of ring capacitive sensor is introduced

that is capacitive fringe effect

and finite element model is established through the Hybrid-Trefftz algorithm

electric field analysis and simulation calculation of different sensor model are done with the finite element software ANSYS

and the optimal structure combination is obtained

and followed the example of optimal structure

the relation between dielectric constant and electric field intensity is given. The result of simulation shows the most direct and the most important two parameters that affect the sensor performance in the design of the ring capacitive sensor are the two electrodes spacing and the length. The smaller the dielectric constant of measured medium is

the greater the intensity of electric field intensity is. The simulation has good theoretical guidance for subsequent product design.