TMR Sensor Feedback Loop for Biomagnetic Resolution
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Solution Overview
Problem
Conventional magnetic sensors with TMR elements and bridge circuits face challenges in measuring weaker magnetic fields due to magnetic saturation, leading to reduced magnetic resolution, which is a limitation in biomagnetic field measurements such as magnetocardiography.
Innovation Solution
A magnetic field measuring device with a sensor unit, reference voltage generating unit, feedback current generating unit, and adjusting unit that adjusts the reference voltage based on output voltage differences to maintain a predetermined range, allowing for the measurement of weaker magnetic fields by generating a feedback magnetic field to diminish the input magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetic sensors with TMR elements and bridge circuits are used, then the device structure is simple, but the magnetic resolution lowers due to magnetic saturation
Solution Approach 1:
The patent implements a feedback mechanism where the output voltage from the TMR element is fed back through an operational amplifier to generate a compensating voltage that is applied to the bridge circuit. This feedback loop dynamically adjusts the operating point of the TMR element, preventing magnetic saturation and maintaining high magnetic resolution throughout the measurement range.
Solution Approach 2:
The patent changes the electrical parameters of the bridge circuit by dynamically adjusting the voltage applied to it based on the output signal from the TMR element. This parameter change allows the bridge circuit to compensate for the nonlinear characteristics of the TMR element and maintain optimal operating conditions, thereby improving magnetic resolution without significantly increasing device complexity.
2Measurement precision
If the magnetic operating point shifts to magnetic saturation region, then the device operation is simplified, but the magnetic resolution lowers
Solution Approach 1:
The feedback mechanism continuously monitors the output voltage from the TMR element and automatically adjusts the bridge circuit voltage to keep the magnetic operating point within the linear region. This eliminates the need for manual calibration and simplifies operation while maintaining high magnetic resolution by preventing saturation.
Solution Approach 2:
The system performs self-adjustment through the feedback loop, where the output signal automatically controls the operating point without external intervention. This self-service mechanism maintains optimal magnetic resolution across varying measurement conditions while keeping the operation simple and automatic.
3Measurement precision
If feedback current is supplied to generate feedback magnetic field, then the magnetic resolution is enhanced, but the device complexity increases
Solution Approach 1:
The operational amplifier in the feedback circuit serves multiple functions: it amplifies the TMR element output signal, generates the compensating voltage for the bridge circuit, and provides the feedback signal to maintain the operating point. This multi-functionality enhances magnetic resolution while minimizing the increase in device complexity by using a single versatile component.
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 enhances magnetic resolution by adjusting the magnetic operating point of the TMR elements, enabling the detection of weaker magnetic fields and reducing variance in feedback current, thereby improving sensitivity and accuracy in biomagnetic field measurements.
Implementation Method 1
one TMR element and three fixed resistors are used to form a bridge circuit
Implementation Method 2
an electrical power for causing a current to flow through a magnetic field generating coil is generated
Data Source
AI summary
A magnetic field measuring device that can measure a weaker magnetic field is provided. A magnetic field measuring device is provided, the magnetic field measuring device including: a sensor unit that has at least one magnetoresistive element; a reference voltage generating unit that outputs a reference voltage; a magnetic field generating unit that generates a magnetic field to be applied to the sensor unit; a feedback current generating unit that supplies, according to a difference between an output voltage of the sensor unit and the reference voltage, the magnetic field generating unit with a feedback current that generates a feedback magnetic field to diminish an input magnetic field to the sensor unit; a magnetic field measuring unit that outputs a measurement value corresponding to the feedback current; and an adjusting unit that uses the output voltage of the sensor unit to adjust the reference voltage.