FINITE-ELEMENT MODELING AS A TOOL FOR DESIGNING CAPACITIVE POSITION SENSORS

In this paper a short overview is given of the methods that are availa ble for modelling the capacitance response of capacitive sensors. This includes the influence of alignment errors and electrode errors (geom etrical errors and defects) as well as parasitic capacitances. Three m ethods are presented: direct calculation of the capacitance by solving the electric-field equations; approximation of the capacitance by sim plifying the electric-field distribution; and modelling using the fini te-element method. The suitability of each of these methods for differ ent purposes is discussed. Conclusions are that in most cases approxim ations based on simplification of the electric field can be used to ge t an impression of the capacitance response, while for more complicate d cases and for higher accuracy the more time-consuming finite-element method can or even must be used.