Magnetic Sensor Array Calibration for Precision Field Detection
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Solution Overview
Problem
Conventional magnetic field measuring apparatuses face challenges in accurately measuring and calibrating magnetic fields due to sensor errors and environmental noise, particularly when using magnetoresistive elements and magnetic flux concentrators, which affect the precision and linearity of magnetic field detection.
Innovation Solution
The apparatus employs a magnetic sensor array with magnetoresistive elements and magnetic flux concentrators, featuring a calibration magnetic field generating unit that produces an alternating magnetic field to calibrate sensor errors, and a signal space separating unit that uses orthonormal functions and basis vectors to separate the target magnetic field from disturbance fields, optimizing sensor calibration and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic sensor array with magnetoresistive elements and magnetic flux concentrators is used to detect magnetic fields, then the sensitivity and detection capability are improved, but sensor errors and environmental noise affect measurement precision
Solution Approach 1:
The patent applies preliminary calibration action by generating a calibration magnetic field before actual measurement to determine sensor characteristics and error parameters. The calibration process pre-characterizes each sensor's sensitivity, offset, and directional response, enabling subsequent compensation during measurement to reduce the impact of environmental noise and sensor errors.
Solution Approach 2:
The patent implements feedback through signal space separation that uses the calibrated sensor characteristics to continuously compensate for sensor errors and environmental interference. The system processes sensor output signals by referencing the calibration data to separate target magnetic fields from noise, providing ongoing correction to maintain measurement precision.
2Measurement precision
If signal space separation is performed to separate target magnetic field from disturbance fields, then the ability to detect weak magnetic fields is improved, but the complexity of data processing increases
Solution Approach 1:
The patent reduces processing complexity by performing preliminary calibration to establish sensor characteristics and basis vectors before actual measurement. This pre-computation of calibration parameters and basis vectors transforms the complex signal space separation problem into a more manageable form that can be efficiently executed during measurement using the pre-determined calibration data.
3Measurement precision
If calibration is performed using a calibration magnetic field generating unit, then sensor error is reduced, but the time required for calibration and measurement setup increases
Solution Approach 1:
The patent employs periodic action by using an alternating calibration magnetic field that oscillates at a specific frequency. This periodic calibration field enables frequency-based separation of calibration signals from DC offset and low-frequency drift, allowing calibration to be performed efficiently without requiring extended measurement periods. The alternating nature of the calibration field facilitates rapid characterization of sensor AC response.
Solution Approach 2:
The patent changes the parameter of the calibration magnetic field from static to alternating at a specific frequency range (10-1000 Hz). This parameter change enables the calibration process to distinguish calibration signals from environmental DC fields and low-frequency noise, reducing calibration time by allowing frequency-domain separation rather than requiring long-time averaging.
4Measurement precision
If magnetic flux concentrators are used to enhance magnetic field detection, then the sensitivity to weak magnetic fields is improved, but the linearity of detection is affected by sensor errors
Solution Approach 1:
The patent applies preliminary calibration to characterize each sensor's actual response to the calibration magnetic field, determining sensitivity factors and offset errors. This pre-measurement calibration establishes the relationship between applied magnetic field and sensor output for each individual sensor, enabling subsequent linearization of the detection system by compensating for manufacturing variations and non-ideal sensor responses.
Solution Approach 2:
The patent changes the operating conditions by applying an alternating calibration magnetic field and measuring sensor response at specific frequencies. This allows determination of frequency-dependent sensitivity parameters that can be used to linearize the sensor response across the operating range, compensating for non-linear effects introduced by magnetic flux concentrators and sensor manufacturing variations.
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 enhances the accuracy and linearity of magnetic field measurement by effectively calibrating sensor errors and suppressing environmental noise, allowing for precise detection of weak magnetic fields such as those from the human heart or other biological sources.
Implementation Method 1
each of the plurality of magnetic sensor cells having a magnetic sensor including a magnetoresistive element
Implementation Method 2
each of the plurality of magnetic sensor cells having a magnetic sensor including a magnetoresistive element and a magnetic flux concentrator
Implementation Method 3
a calibration magnetic field generating unit for generating a calibration magnetic field at a position on a straight line that can be drawn without crossing the plurality of magnetic sensor cells from the measurement space outside the measurement space
Implementation Method 4
a signal space separating unit for performing signal separation on a magnetic field spatial distribution indicated by the measurement data based on a position and magnetic sensitivity of each magnetic sensor
Data Source
AI summary
Provided is a magnetic field measuring apparatus for: acquiring the measurement data measured by a magnetic sensor array that is configured by arraying the plurality of magnetic sensor cells to form a surface covering at least a part of a target object to be measured; performing signal separation on a magnetic field spatial distribution indicated by the measurement data based on a position and magnetic sensitivity of each magnetic sensor; generating a calibration magnetic field at a position on a straight line that can be drawn without crossing the plurality of magnetic sensor cells from the measurement space outside the measurement space; and calibrating a sensor error for the magnetic sensor based on a separation error in a case where signal separation has been performed on a spatial distribution of the calibration magnetic field.