A non‐contact gap measurement method for narrow and irregular targets using inductive planar sensors with simple calibration

Abstract

Planar inductive sensors are widely used for non‐contact gap measurement. Usually, a change in size, shape, or material of the target requires a tedious recalibration of the measurement setup. This paper aims to present a new method to measure the gap from irregular and narrow targets using a planar inductive sensor without this tedious calibration process. The magnetic field distribution on this target was numerically studied, and the findings suggested that a simpler calibration would work by modeling the induced current in the target as a virtual planar coil. For this target, we found that the calibration curves corresponding to different materials can be obtained by adding a constant C to the base curve. To validate this approach, three planar coils of different sizes were tested with four metallic turbine blade‐shaped targets. Results showed that the measured gaps matched well with the real gaps, with a maximum error of about 3.703%. The new approach can be applied to various applications including 3D printer build platform calibration, bandsaw blade deviation detection, and blade tip clearance monitoring.