Research Of Measuring Methods Of Aperture Measuring Capacitance Sensor

Measuring the aperture of holes is a significant aspect of geometrical measuring, and it has the following properties. Firstly, the active space of metrical tools is limited in a narrow scope. Secondly, manipulation and adjustment of measurement are inconvenient. Thirdly, the measurement is inefficient and the aperture of very small holes is almost unable to measure at present. So far people haven't found a handy and inexpensive way to obtain the exact aperture of small holes whose diameters are belowΦ3mm.Capacitance sensor is an important technology for non-contact evaluation. Using capacitance sensor not only can measure the aperture of small blind holes and through holes, but also can obtain their shape errors of arbitrary cross-section and no influence of measuring force.In this dissertation, we analyzed the principle of aperture measuring capacitance sensor, which includes gauge head, measuring circuit and measuring software. The calculation method of the least protecting ring width bmin on the sensor's measuring electrode is studied. In addition, the method of design and process ofΦ3mm gauge head of the aperture measuring capacitance sensor is studied. And the calibration procedure of the aperture measuring system is presented based on analyzing its error. Finally, in the validating experiment we can find that the aperture measuring system has long-time stability and reliability, and the maximum offset is less than 0.23μm.In all, we studied a convenient and low-cost solution for measuring the aperture of small holes of diameters aroundΦ3mm. Our work will be beneficial to future research in the field of measuring aperture of smaller holes.