A coaxiality measurement method by using three capacitive sensors

Abstract This paper describes a method of determining the coaxiality errors between suspended coil and outer magnet yoke by using three capacitive sensors. The coaxiality error sources including the cylindrical error of the outer yoke of the magnet, the movement trajectory straightness error of the lifting stage and the tilt error of the suspended coil are identified. Three capacitive sensors are used to measure the coaxiality eccentric errors. The theoretical model and the mathematical relationship between the outputs of three capacitive sensors and the coaxiality errors are established. The method has an advantage that the third radial redundancy sensor can be used to eliminate the influence of the form and the size. And the experiments are conducted to measure the coaxiality errors.