GMI Magnetic Field Sensor with Feedback Coil Control
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Solution Overview
Problem
Current magnetic field measurement devices, such as fluxgates and giant magneto-impedance magnetometers, face limitations in measurement bandwidth and sensitivity, with fluxgates offering limited bandwidth and requiring encapsulation and thermal drift compensation, while giant magneto-impedance sensors have variable sensitivity dependent on the probe used.
Innovation Solution
A magnetic field measurement device featuring a control circuit with a correction module to control a working magnetic field generated by a feedback coil, optimizing probe sensitivity and minimizing noise, and utilizing a dual modulated electrical current and a single coil functioning as both pick-up and feedback coils to enhance sensitivity and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If giant magneto-impedance magnetometers are used to achieve higher measurement bandwidth, then measurement bandwidth is improved, but sensitivity becomes variable and dependent on the probe used
Solution Approach 1:
The patent applies parameter changes by systematically varying the DC magnetic field strength (Hdc) to optimize probe sensitivity. The control circuit adjusts the DC current through the feedback coil to establish an optimal working point where the probe's impedance variation is maximized, thereby achieving consistent high sensitivity across different probes while maintaining the high bandwidth characteristics of GMI magnetometers.
Solution Approach 2:
The patent implements feedback control by using the pick-up coil to detect the probe's response and feeding this information back to the control circuit. The control circuit then adjusts the DC magnetic field to maximize the detected signal, creating a closed-loop system that automatically optimizes sensitivity regardless of probe variations, thus resolving the sensitivity consistency issue.
2Measurement precision
If fluxgates are used to achieve precise measurement, then measurement precision is improved, but measurement bandwidth is limited
Solution Approach 1:
The patent applies dynamics by using a high-frequency AC current (0.5-100 MHz) through the probe in addition to the DC current. This dynamic excitation enables the GMI effect to operate at high frequencies, achieving measurement bandwidths much higher than traditional fluxgates while maintaining precision through the optimization of the DC bias field and the use of signal detection circuits.
3Device complexity
If a single coil is used to function as both pick-up and feedback coils, then device complexity is reduced, but control capability may be compromised
Solution Approach 1:
The patent applies universality by designing a single coil that performs multiple functions: it serves as both the feedback coil (generating DC magnetic field) and the pick-up coil (detecting probe response). The control circuit intelligently switches between these functions by controlling current flow direction and magnitude, thereby reducing device complexity without compromising control capability through sophisticated electrical control strategies.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device achieves improved sensitivity and reduced noise, making it easier to implement and use, with a sensitivity of 100 kV/T to 200 kV/T and temperature sensitivity lower than 2 nT/K, while allowing for multidimensional magnetic field measurements.
Implementation Method 1
GMI magnetometers comprise probes, generally formed from an amorphous wire, which are characterized by a large variation of their impedance when they are driven by a high-frequency current and subjected to an external magnetic field parallel to the main axis direction of the probe.
Implementation Method 2
a pick-up coil surrounds the probe of the GMI magnetometer. This pick-up coil is configured to sense a signal depending on the magnetic field generated by the high-frequency current in the probe
Implementation Method 3
a correction module connected to the preamplification module and to the buffer module, and being configured to control a working magnetic field generated by the feedback coil around the probe
Data Source
AI summary
This device for measuring a magnetic field comprises:a magnetic field sensor, comprising:a probe, anda pick-up coil and a feedback coil coiled around the probe, anda control circuit, comprising:a generation module comprising a probe signal generation unit, configured to generate an electrical current,a preamplification module,a buffer module, configured to deliver an output signal of the control circuit defining an output magnetic field value,a piloting module configured to pilot the probe signal generation unit to generate the electrical current in the probe.The control circuit comprises a correction module configured to control a working magnetic field, corresponding to a magnetic field maximizing the magnetic field sensitivity of the probe and minimizing the magnetic field noise of the probe.