Design of a non-contact strain sensor based on amorphous ribbons

• A novel non-contact sensor is developed in favor of simplicity, low cost and miniaturization.
• A planar spiral coil combined with a Colpitts oscillator, in variation of impedance on the film coupled with the coil.
• The sensor does need to require complex hardware circuits and some expensive devices.
• We report a gauge figure of merit is approximately 5167.

Based on the magnetoelastic effect, this study develops a non-contact strain sensor consisting of a magnetoelastic film by using low-priced and highly-sensitive Metglas 2826MB (Fe40Ni38Mo4B18) amorphous ribbons as the strain measure material. Furthermore, a planar spiral coil combined in a Colpitts oscillator circuit is used to excite the magnetoelastic film. Under a tensile load, a mechanical deformation of the amorphous ribbons occurs and alters its permeability and conductivity, and induces an eddy current on the surface of the amorphous ribbons. This results in a variation of impedance on the film coupled with the planar spiral coil as well as in the corresponding voltage output to be measured. The experimental results show that the measurement sensitivity can reach 6.9 mV/MPa, and the corresponding gauge factor is approximately 5167. The advantages are a simplified manufacturing process, uniformity in coil characteristics, compactness, uncomplicated circuit architecture, and low manufacturing cost. Moreover, a promising potential for further improvement makes the designed sensor suitable for future practical applications.