Magnetometer Without Servo Control for Dense Sensor Arrays
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Solution Overview
Problem
In networks of magnetometers used for magnetocardiography or magnetoencephalography, the compensation magnetic field generated by one magnetometer interferes with nearby sensors, leading to measurement instabilities and errors, especially when sensor spacing is too close to effectively mitigate these issues.
Innovation Solution
A device and method that measure the magnetic field by directly utilizing the amplitude of resonances at the oscillation frequency of an excitation source, without servo-control in zero magnetic fields, and employ a secondary excitation source to provide a reference signal for calibrating the resonance slope, allowing for interference suppression and accurate field component measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetometers are spaced several centimeters apart to avoid interference, then measurement stability is improved, but the array cannot be used in applications requiring dense spacing (magnetocardiography or magnetoencephalography where spacing is 1 to 2 centimeters)
Solution Approach 1:
The patent extracts and eliminates the compensating magnetic field BC that causes interference. By removing the servo control system that generates this field, the magnetometer can operate in dense arrays without interfering with neighboring sensors, thus maintaining measurement stability at small spacings.
Solution Approach 2:
The patent changes the operating parameters by removing the zero-field servo control mechanism. This parameter change allows the magnetometer to function without generating compensating fields, enabling dense array configurations while maintaining measurement reliability.
2Measurement precision
If zero-field servo control is used to measure magnetic fields, then measurement precision is improved, but compensating magnetic fields generated interfere with nearby magnetometers in the network
Solution Approach 1:
The patent removes the compensating magnetic field BC generation mechanism from the system. By taking out the servo control that creates this harmful field, nearby magnetometers are no longer interfered with, while measurement precision is maintained through alternative methods.
Solution Approach 2:
The patent converts the harmful compensating field into a beneficial reference signal. By using the excitation field as a reference for calibration and processing the signal at the excitation frequency, the system achieves precise measurements without the harmful side effects of traditional servo control.
3Adaptability or versatility
If magnetometers operate in dense arrays with small spacing, then application feasibility for magnetocardiography or magnetoencephalography is improved, but measurement stability deteriorates due to interference from compensating fields
Solution Approach 1:
The patent extracts and removes the source of interference (compensating magnetic field) enabling dense array operation. This allows the system to be adapted for magnetocardiography and magnetoencephalography applications with 1 to 2 cm spacing while maintaining measurement stability.
4Measurement precision
If secondary excitation source is added for calibration, then measurement accuracy is improved through real-time resonance slope calibration, but device complexity increases
Solution Approach 1:
The patent makes the excitation coil serve multiple functions: it acts as both the measurement excitation source and the calibration reference source. This multi-functionality reduces device complexity while enabling real-time resonance slope calibration through the secondary excitation signal.
Solution Approach 2:
The patent merges the calibration function with the measurement excitation function. By combining these functions and using the same coil for both purposes with different signal frequencies, the device complexity is minimized while achieving accurate real-time calibration.
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
This approach reduces interference between magnetometers, enables accurate measurement of weak magnetic fields, and allows for real-time calibration, improving the reliability of magnetic field reconstruction in dense sensor arrays.
Implementation Method 1
an alternating excitation current is applied to an excitation coil surrounding a magnetic core
Implementation Method 2
measuring the amplitude of a signal at a harmonic of an oscillation frequency of an excitation source
Implementation Method 3
these pulses resonate at harmonics of the excitation current frequency. The amplitude of the even harmonics is proportional to the field being measured
Implementation Method 4
a laser source that emits a polarized beam towards the cell along a propagation direction
Implementation Method 5
A coil surrounds the cell, powered by a frequency generator to generate a sinusoidal excitation magnetic field, perpendicular to the propagation direction and parallel to the field to be measured
Data Source
Figure 1~3
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Figure 6
AI summary
The invention relates to a magnetometer (10) comprising a detector (13, 14) configured to measure the amplitude of an output signal at an oscillation frequency and to deduce therefrom a component of a magnetic field to be measured from the value of a resonance slope, characterized in that it comprises a primary excitation source providing a measurement signal (B1) oscillating at a primary oscillation frequency and a secondary excitation source providing a reference signal of known amplitude (B2) oscillating at a secondary oscillation frequency, the detector being configured to measure the amplitude of the output signal at a harmonic of the secondary oscillation frequency and to deduce said resonance slope. The invention also extends to an array of magnetometers as well as to a method for measuring a magnetic field without feedback control and with compensation for fluctuations in the resonance slope.