Development of chipless, wireless current sensor system based on giant magnetoimpedance magnetic sensor and surface acoustic wave transponder

Non-Contact Current Sensing System Based on the Giant Magnetoimpedance Effect of CoFeNiSiB Amorphous Ribbon Meanders

A sensitive non-contact sensing system based on the CoFeNiSiB amorphous ribbon giant magnetoimpedance (GMI) effect is proposed for current testing. The sensing system consists of a GMI probe, a sinusoidal current generator, a voltage follower, a preamplifier, a low-pass filter, and a peak detector. Four different GMI probes derived from amorphous ribbon meanders are designed and fabricated through MEMS processes. GMI probes were driven by a 10 MHz, 5 mA AC current. A permanent magnet was used to provide a bias magnetic field for the probe. The effect of the bias magnetic field on the output DC voltage was investigated. This non-contact current sensing system exhibits good sensitivity and linearity at a bias magnetic field Hbias = 15 Oe. The sensitivity can reach up to 24.2 mV/A in the ±1.5 A range.

Visual management of medical things with an advanced color-change RFID tag

This paper proposes a visual management scheme of medical things with a color-change radio frequency identification (RFID) tag. The color-change RFID tag employs a specific RFID tag integrated circuit (IC) and a laminated pH-indicating paper. The IC has energy harvesting and switched ground functions, which enable it to generate electricity to the laminated pH-indicating paper. This phenomenon causes electrolysis of NaCl solution absorbed in the laminated pH-indicating paper. Electrolysis generates alkaline matter to change the color of the pH-indicating paper. This paper gives a new and sensitive structure of the laminated pH-indicating paper. The proposed advanced color-change RFID tag with new laminated pH-indicating paper succeeds in changing its color noticeably at a 1 m distance using an RFID reader radiating 1 W radio waves. The color change was observed 3-5 s after starting radio wave irradiation. The results of this experiment also confirm that the changed color can be held for over 24 h. Furthermore, two demonstrations of the visual management system of medical things (patient clothes and sanitizers) are presented.

Observation of the transition state of domain wall displacement and GMI effect of FINEMET/graphene composite ribbons

In this paper, the morphology, structure, and magnetic properties of FINEMET/graphene composite ribbons are systematically studied by SEM, Raman and static methods (hysteresis loops) and the dynamic method (giant magneto-impedance effect, GMI) respectively. It is revealed that with the increase of the number of graphene layers, the GMI effect of the FINEMET/graphene composite ribbons decreases, and the anisotropy field and the relaxation frequency of domain wall displacement of FINEMET/graphene composite ribbons increases. The result also confirmed that graphene does regulate the magnetic properties of FINEMET ribbon. Therefore, a comprehensive analysis of the influence of graphene on the magnetic properties of FINEMET ribbon is of important guiding significance in industrial applications.

In this paper, the morphology, structure, and magnetic properties of FINEMET/graphene composite ribbons are systematically studied by SEM, Raman and static methods (hysteresis loops) and the dynamic method (giant magneto-impedance effect, GMI) respectively.