Magnetic-Field Sensor Feedback Coil for Stray Field Cancellation
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Solution Overview
Problem
Magnetic-field sensors face sensitivity issues due to stray magnetic fields, which can mask the non-linear behavior of certain magnetoresistance elements, affecting their accuracy in detecting target positions.
Innovation Solution
A magnetic-field sensor design incorporating a feedback loop with a secondary coil circuitry that generates a compensatory magnetic-field signal to mitigate stray magnetic-field effects, improving sensitivity and accuracy by distinguishing between desired and stray signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetoresistance elements are used for magnetic field sensing, then the sensor can detect target position, but stray magnetic fields from the sensing element itself mask the reflected signal and reduce measurement precision
Solution Approach 1:
The patent implements a feedback mechanism where the sensing element's output is fed back through a feedback coil to generate a compensating magnetic field. This feedback loop detects the stray field effects and actively counteracts them, allowing the system to maintain measurement precision despite the presence of harmful stray fields from the sensing element itself.
Solution Approach 2:
The patent converts the harmful stray magnetic fields generated by the sensing element into a useful signal by using a feedback coil to transform them into a compensating field. The stray fields that were previously masking the reflected signal are now harnessed to drive the feedback mechanism that eliminates their harmful effects, turning a disadvantage into an advantage.
2Use of energy by moving object
If the magnetic field sensing element generates strong magnetic field signals, then the sensor can detect targets at greater distances, but the stray magnetic field effects increase and mask the reflected signal
Solution Approach 1:
The feedback mechanism continuously monitors the sensing element's output and generates a compensating field proportional to the stray field effects. This allows the system to operate with stronger magnetic field signals for extended detection range while the feedback actively cancels the proportionally increased stray field interference, maintaining measurement precision across varying signal strengths.
Solution Approach 2:
By converting the harmful stray fields into a compensating feedback signal, the system enables stronger primary magnetic field generation for greater detection range. The harm of increased stray fields at higher energy levels is transformed into the benefit of a stronger compensating signal that precisely counteracts the interference, allowing extended range operation without precision loss.
3Device complexity
If magnetoresistance elements with limited linear range are used, then the sensor can be made more compact, but the usable detection range is reduced
Solution Approach 1:
The feedback mechanism linearizes the response of magnetoresistance elements with inherently limited linear ranges by actively compensating for their non-linear behavior. This allows the use of compact magnetoresistance-based sensing elements while the feedback loop extends the effective linear detection range, reconciling structural compactness with operational versatility.
Solution Approach 2:
The feedback system dynamically adjusts the magnetic field parameters to maintain operation within the linear range of compact magnetoresistance elements. By changing the field strength and characteristics through feedback control, the system extends the usable detection range beyond the inherent limitations of the compact sensing elements, achieving both compactness and adaptability.
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 solution effectively reduces the impact of stray magnetic fields, enhancing the sensor's ability to accurately detect target positions and compensate for non-linear behaviors in magnetoresistance elements, thereby improving overall sensor performance.
Implementation Method 1
main coil circuitry configured to generate a first magnetic-field signal at a first frequency; a reflected signal is generated from a target caused by the first magnetic-field signal
Implementation Method 2
A linear range refers to a range where changes in a magnetic-field intensity is linear with changes in resistance. Some magnetoresistance elements, such as a TMR, have a limited linear range.
Implementation Method 3
secondary coil circuitry configured to receive the second feedback signal and to generate, based on the second feedback signal, a second magnetic-field signal to reduce the first magnetic-field signal received at the first magnetoresistance circuitry
Data Source
AI summary
In one aspect, a magnetic-field sensor includes main coil circuitry configured to generate a first magnetic-field signal at a first frequency; a first channel; a second channel; a subtractor circuit configured to subtract a second channel output signal from a first channel output signal to form a subtraction signal; an adder circuit configured to combine the first channel output signal and the second channel output signal to form a summation signal; processing circuitry configured to receive the summation signal and to provide a magnetic-field sensor output signal indicating a position of the target; feedback circuitry configured to receive the subtraction signal and to provide a first feedback signal to the processing circuitry, and a second feedback signal; and a secondary coil circuitry configured to receive the second feedback signal and to generate, based on the second feedback signal, a second magnetic-field signal to reduce the first magnetic-field signal received.