Magnetic Field Sensor Current Reversal for Offset Cancellation
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Solution Overview
Problem
Existing magnetic field sensors face limitations in accuracy, particularly in measuring peak voltages and detecting the strength and direction of ambient magnetic fields, due to issues with DC offset components and limited calibration times.
Innovation Solution
A magnetic field sensor design incorporating a microprocessor with integrated switches, a voltmeter, and an analogue-to-digital converter, along with a magnetic sensing element, which reverses current flow through the sensing element to improve measurement accuracy and direction determination, utilizing a timer to store and calculate the difference in voltage readings across the sensing element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If peak voltage measurement is used in a flux meter, then the magnetic field can be detected, but the measurement accuracy is limited
Solution Approach 1:
The patent applies periodic action by reversing the direction of electrical current through the magnetic sensing element between successive voltage measurements. This creates alternating current cycles that allow the system to measure voltage differences over time, transforming the measurement from a single peak voltage reading to a time-dependent voltage difference measurement, thereby improving accuracy and reliability
Solution Approach 2:
The patent implements feedback by using the voltmeter to continuously monitor the voltage across the magnetic sensing element and comparing successive voltage readings. The system uses the voltage difference between consecutive measurements to determine magnetic field strength, creating a feedback loop that continuously refines the measurement and improves both accuracy and reliability
2Duration of action of stationary object
If DC offset component is present in the measurement system, then the system can operate continuously, but the magnetic flux measurement accuracy is compromised
Solution Approach 1:
The patent uses periodic action by reversing current direction between successive measurements. This creates a time-varying voltage signal where the DC offset component appears as a constant background while the magnetic field-induced voltage varies with the current reversal. By measuring the voltage difference between successive reversals, the system effectively subtracts the DC offset, enabling continuous operation without compromising measurement accuracy
Solution Approach 2:
The patent converts the harmful DC offset component into a beneficial feature by using the voltage difference between successive measurements. The DC offset, which would normally degrade accuracy, is eliminated through the differential measurement approach, allowing the system to maintain continuous operation while achieving high measurement precision
3Measurement precision
If calibration time is extended to improve accuracy, then measurement precision improves, but the time required for calibration increases
Solution Approach 1:
The patent applies self-service by enabling the sensor to perform automatic calibration using its own voltage readings. The microprocessor automatically compares successive voltage measurements, determines the calibration constant, and stores it for use in subsequent measurements. This eliminates the need for manual calibration procedures, achieving high measurement precision while minimizing time loss through automated, self-performing 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 enhances the accuracy of magnetic field strength and direction measurements, allowing for more precise determination of ambient magnetic components and enabling the sensor to function as a compass by calculating the difference in successive voltage readings, thereby improving the overall performance of the magnetic field sensor.
Implementation Method 1
a magnetic sensing element, a voltmeter connected in the circuitry to provide a measure of the voltage across the magnetic sensing element
Data Source
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AI summary
A magnetic field sensor for determining the strength and/or direction of a component of an ambient magnetic field. It comprises electrical circuitry which incorporates a magnetic sensing element, a voltmeter connected in the circuitry to provide a measure of the voltage across the magnetic sensing element, an electrical energy supply connector connected to the magnetic sensing element to supply an electrical current which passes through that element when the sensor is in use, and switches to reverse the direction of the flow of electrical current through the magnetic sensing element between successive measurements of the said voltage by the said voltmeter. The magnetic sensing element comprises a coil surrounding magnetic material. The electrical energy source connector and the said switches are connected to the said coil. The voltmeter is connected to measure the voltage across the said coil. The circuitry further comprises a timer connected within the circuitry to cause the voltmeter to provide measurements V1 and V2 respectively at times T1 and T2 which occur after successive operations of the switches respectively at times T0 and T5, to initiate the passage of electrical current through the coil in respective opposite directions, such that T1 - T0 = T2 - T5 = ΔΤ, where ΔΤ is a predetermined period of time. A processor is connected in the circuitry to provide an indication of the value of V1-V2, the magnitude of which provides an indication of the strength of the said component, and the sign of which provides an indication of the direction of the said component. Also, a method of determining the strength and/or direction of a component of an ambient magnetic field using such a sensor.