Real-time measurement of eccentric motion with low-cost capacitive sensor

In the operation of rotating machinery, the axial tilt of a rotor is an inevitable phenomenon and often as important as its radial error motion. The cylindrical capacitive sensors (CCSs) have been developed and applied to measure such kind of errors in the past two decades. Compared with other competing sensors, such as optical, inductive, and piezoresistive transducers, CCSs have many advantages, such as low cost and power usage, and good stability, resolution, and speed, etc. In this paper, a new approach that measures the eccentric motions of a hydraulic pump by using a CCS is presented. With this proposed method, the eccentric motion can be acquired in real time with a carrier signal by a circuit of low-cost capacitance-to-digital converter. The analytical results are compared and verified with experiments.