Design and Optimisation of a PCB Eddy Current Displacement Sensor

Abstract

Position sensing is one of the crucial parts of many systems, specifically in an active magnetic bearing. The position is used to control the magnetic forces within an active magnetic bearing to keep a rotor levitated. Sensors used in these systems must be very sensitive and are usually very expensive. In this paper a low cost printed circuit board position sensor is analysed. The sensor uses an excitation coil to establish a magnetic field. Four sensing coils are then used to measure the influence a conducting target has on the magnetic field to enable position sensing. The sensor's magnetic operation is analysed using finite element methods and very good correlation is found with measured results. The effects of the target material and the number of PCB layers are analysed. It is shown that a two layer sensor can produce acceptable sensitivity and linearity.

Driver Circuit Design for a New Eddy Current Sensor in Displacement Measurement of Active Magnetic Bearing Systems

“…The TFS model of ( 1)-( 4) has been developed and investigated in [15] by the PEEC method. A further and thorough analysis of the various influence factors on the sensitivity is conducted in [13] and [14] using the 2-D and 3-D FEM, respectively. The used TFS design in this article is proposed according to the analysis in [14], and it is specified in Table I.…”

“…The TFS is further developed for high-temperature AMBs using the thick-film manufacturing techniques in [11]. Furthermore, the sensor is modeled by different methods including the 2-D finite element model (FEM) [12], [13], 3-D FEM [14], and partial element equivalent circuit (PEEC) method [15], and optimal design laws for the TFS are summarized by comprehensively analyzing various parameters regarding the sensor performance.…”

Magnetic position sensors

“…Low-cost eddy current displacement sensors can be produced in PCB technology. A useful design case is shown in [44]. The working frequency of these sensors is 1-10 MHz.…”

A magnetic head-based eddy current displacement sensing method

“…In [18], a printed circuit board ECDS was designed for use in AMBs. When the sensor was employed, differential measurements of opposite coils were used to reduce the influence of common mode effects such as magnetic interference.…”