| As a non-contact instrument for small-distance measurement, the high accuracy capacitance micrometer has many advantages such as wide measuring range, simple structure, easy to use etc. However, the traditional capacitance micrometer (double parallel electrodes capacitance sensor) has many defects, such as volume and install limits.The characteristics of traditional capacitance micrometer are outlined. On this basis, a new type of capacitance sensor structure is proposed, which is different from traditional capacitance micrometer. It has the two electrodes installed on the same side which can be called single-chip capacitance sensor. It can realize non-contact measurement in high definition and efficiency, so it will be widely used in the modern industry measurement and has a great prospect in the future.The electric field generated by this single-chip capacitance sensor is scattering, so it is hard to use the traditional electromagnetic theory to obtain accurate analytical solutions, which causes great difficulties to optimize the sensor performance. Using ANSYS finite element simulation combined with the specific way of experiment, the relationship between the electrode separation, thickness of electrodes and sensitive range of sensor are analyzed in this thesis.Using printed circuit board (PCB) technology,6 different structural parameters of the sensor are made. For metal and nonmetal materials measured, the simulation conclusions are verified:compared with simple single-chip capacitance sensor, the single-chip capacitance sensor with complicated electrodes has larger initial capacitance and higher sensitivity, and its characteristic is better than the former for a given sensor area.Different parameters have different influence to the sensor characteristics. The conclusions are:1) with the increase of electrode separation, the range of sensor increases while its sensitivity decrease; 2) the double-interdigital electrode sensor has lager range and higher sensitivity than the zaozi pattern sensor in the condition of same electrode separation; 3) the sensitivities of 6 sensors are linear by section, each section has different sensitivity. The closer the object being measured is, the higher sensitivity could be. The sensor designed in this thesis can work well for both metal and nonmetal objects:it has a range of 6000μm, sensitivity of 3.8fF/μm for metal objects and has a range of 170μm, sensitivity of 6.2 f F/μm for non-metal objects.Finally the fit method of nonlinear relationship between capacitance (altered into voltage later) and the measured distance is discussed.Using Proteus software, the overall program feasibility has been demonstrated, and the nonlinear correction of the prototype can be realized to a certain extent. |
