Device and method for detecting surface weak magnetic fields based on giant magneto-impedance effect

A magnetic field measurement method comprising:

• positioning a giant magneto-impedance probe at a first position near a surface of an object to be measured;
• applying an AC current to the giant magneto-impedance probe and measuring a first AC voltage of the probe;
• calculating impedance of the giant magneto-impedance probe based on the AC current and the first AC voltage, and determining a first magnetic field based on the impedance;
• positioning the giant magneto-impedance probe at a second position above the first position;
• applying the AC current to the giant magneto-impedance probe and measuring a second AC voltage of the probe;
• calculating impedance of the giant magneto-impedance probe based on the AC current and the second AC voltage, and determining a second magnetic field based on the impedance;
• calculating a measurement magnetic field at the first position near the surface of the object to be measured based on the first magnetic field and the second magnetic field.

A magnetic field detection device, comprising:

• a vibrating head on which a giant magneto-impedance GMI probe is mounted;
• an alternating current AC signal source configured to apply an AC current having a first frequency to the GMI probe;
• a vibration controller configured to control the vibrating head to vibrate at a second frequency based on a reference signal having a second frequency;
• a measurement circuit configured to measure an AC voltage signal at the first frequency provided by the GMI probe when the AC current at the first frequency is applied to the GMI probe, and generate a measurement signal indicating an amplitude of the AC voltage signal;
• an interlock circuit configured to extract the amplitude of the measurement signal based on the reference signal at the second frequency and provide the reference signal at the second frequency to the vibration controller;
• and
• a calculation unit configured to determine a magnitude of a magnetic field measured by the GMI probe based on the amplitude of the measurement signal.