Temperature Drift Characteristics Analysis of GMM-FBG Current Sensor Based on Finite-Element Multi-Physics Simulations

A composite current sensor is designed with soft ferrite as the magnetizer in combination with giant magnetostrictive material (GMM) and fiber Bragg grating (FBG). The temperature drift characteristics of the GMM, detecting performances under thermal strain caused by temperature variation in the GMM rod, are investigated by simulating the coupled fields of magnetostriction and thermal expansion with the finite-element multi-physics method to explore the temperature-drift mechanism of the ferrite–GMM current detector. The sensing characteristics of the GMM-FBG current sensor under quasi-static current excitation at various work temperatures are evaluated by simulating thermal stress between the GMM and FBG to analyze the temperature drift mechanism of the Bragg wavelength signal modulated by FBG. Even though temperature elevation suppresses GMM magnetization and thereby reduces the slopes of stress–strain curves, the steering magnetization of magnetic domains in the GMM rod tends to saturation without appreciable thermal inhibition in the high-stress region of large current excitation, while the magnetostrictive strain is still abated by the reduction in magnetic flux density caused by the thermal expansion of GMM rods. The temperature elevation can also produce thermal stress between the GMM and FBG, which will decrease the detection sensitivity and testing range of the GMM-FBG current sensor. The temperature drift characteristics of the GMM-FBG are generalized into a formula by fitting the wavelength shifting as a function of thermal strain, which will significantly facilitate designing the scale calibration for various ambient temperatures. The present researchers provide a theoretical basis and experimental guidance for developing GMM-FBG current sensors with high sensitivity and stability.