Customization of Digital Circuit for Material-Independent Eddy Current Proximity Sensor for Active Magnetic Bearings

The state of the art, commercial eddy current sensors can provide excellent quality of the measured position; however, the easier system integration, size of the conditioning electronics, cost, and interfacing delays are unfavorable. In this paper, a customization of the basic conventional single-coil eddy current proximity sensor for active magnetic bearings is presented. The signal conditioning is designed to be integrated with the main signal processing unit, which can also incorporate the active magnetic bearing system controller. The nonlinearities and dependencies on the electromagnetic properties of the target material are eliminated using software implementation. The highest signal to noise ration is observed for the aluminium-alloy target. It is shown that for the studied sensor the measuring range and accuracy are limited when under the materialindependent operation.