Influence of bias magnetic field for sleeve eddy current sensor (SECS) in tension measurement

According to the inverse magnetostrictive effect, magnetic permeability variations in ferromagnetic materials under elastic stress offer the potential to measure tension. In this study, a prototype sensor was designed, fabricated, and tested. An eddy current sensor (ECS) with a single coil structure was used to detect tension due to its lower cost, simpler structure and less mutual interference than that of conventional elastomagnetic (EM) sensors. In addition, the influence of a sleeve structure on the ECS was investigated through experimental studies. The experimental results indicated that the use of sleeve structure could enhance the relative sensitivity and reduce the repeatability error of the sensor. Furthermore, a bypass structure was designed to adjust the bias magnetic field by changing air gap in the lower magnetic circuit or by rotating yoke in the upper magnetic circuit. The results demonstrated a linear relationship between voltage across the sensor and tension. Finally, the bias magnetic field and working frequency were optimized by monitoring the sensor sensitivity.