Low Field Optimization of a Non-Contacting High-Sensitivity GMR-Based DC/AC Current Sensor

Area of Science:

• Electrical Engineering
• Materials Science
• Sensor Technology

Background:

• Galvanic isolation is crucial for current measurement devices, especially for DC and low currents where traditional methods are insufficient.
• Giant magnetoresistance (GMR) sensors offer a promising alternative but require optimization for sensitivity and linearity.

Purpose of the Study:

• To develop a practical method for enhancing the sensitivity and linearity of GMR-based current sensors.
• To adapt the GMR sensor for detecting magnetic nanoparticles (MNPs) in lab-on-a-chip applications.

Main Methods:

• Utilized a multi-trace current trace and a double differential GMR detection system to create a planar coil.
• Developed an analytical model to calculate the magnetic field generated by current in the GMR sensing area.
• Implemented an experimental setup for measuring DC and AC currents within a specific range.

Main Results:

• Achieved a significant increase in sensitivity, up to 13 times compared to a single biased sensor.
• Demonstrated measurement of DC and AC currents from 2-300 mA with sensitivities of 15.62 to 23.19 mV/mA.
• Established a detection limit of 100 μA for DC and 100-300 μA for AC currents (10 Hz to 50 kHz).
• Exhibited high immunity to external magnetic fields and a low temperature drift of -2.59 × 10^-4 A/°C due to the differential setup.
• Successfully adapted the setup for magnetic nanoparticle detection, reporting preliminary results.

Conclusions:

• The proposed GMR sensor design significantly improves sensitivity and linearity for low current measurements.
• The double differential setup provides robustness against external magnetic fields and temperature variations.
• The adaptable GMR sensor shows potential for applications in biomolecular labeling and lab-on-a-chip systems.