Differential capacitive multi-axis distance sensor system for environments with electromagnetic noise

In this article, a capacitive distance measurement system with a novel evaluation circuit is described which operates according to the principle of amplitude modulation and is evaluated multi differentially. Due to the use of differential sensors, the influence of the capacitance between the object and ground is compensated and the immunity against potential changes of the measuring object is increased significantly compared to conventional capacitive measuring systems. The evaluation circuit is designed for extra high carrier frequencies, which reduces the influence of electromagnetic noise up to single-digit MHz range. By means of synchronisation, any number of single measuring systems can be combined to form a noise immune multi-axis measuring system, which especially meets the high requirements of the active magnetic bearing technology.