AC Hall Sensor Frequency Shifting for Phase-Independent Magnetic Field Measurement
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Solution Overview
Problem
Conventional Hall effect sensors for measuring AC magnetic fields are limited by the need for complex switching circuitry and are prone to parasitic offset and induced signals, especially when measuring time-varying magnetic fields at unknown frequencies, requiring exact frequency and phase matching.
Innovation Solution
A method where the current to the Hall sensor is driven at a known frequency, allowing the output Hall voltage to be characterized in a specific frequency range, enabling phase-independent measurement of magnetic field spectral components without prior knowledge of the magnetic field frequency, thus overcoming the limitations of exact frequency and phase matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional Hall effect sensors use current spinning to measure AC magnetic fields, then measurement capability is provided, but complex switching circuitry is required and frequency limits are imposed
Solution Approach 1:
The patent extracts and eliminates the current spinning switching circuitry from the measurement system. Instead of using active switching transistors to modulate the current, the invention drives the Hall sensor with a continuous AC current at a known frequency, removing the complex switching infrastructure while preserving AC magnetic field measurement capability
Solution Approach 2:
The patent applies periodic action by driving the Hall sensor with AC current at a known frequency θ rather than using DC current with switching. This periodic current drive naturally modulates the Hall voltage at frequencies θ±ω, enabling AC magnetic field measurement without requiring active switching circuitry
2Adaptability or versatility
If Hall effect sensors measure time-varying magnetic fields, then AC magnetic field measurement is achieved, but parasitic offset and induced signals are generated
Solution Approach 1:
The patent moves the measurement to a different frequency dimension. By driving the Hall sensor at frequency θ and measuring the Hall voltage at frequencies θ±ω rather than at the magnetic field frequency ω itself, the measurement operates in a shifted frequency domain where parasitic offset and induced signals do not interfere
Solution Approach 2:
The patent converts the typically harmful parasitic offset and induced signals into beneficial frequency separation. The offset signal appears at frequency θ and the induced signal at frequency ω, while the useful Hall signal appears at frequencies θ±ω. This frequency separation allows easy filtering and extraction of the useful signal while rejecting the parasitic components
3Measurement precision
If previous harmonic signal techniques are used, then Hall signal at twice the frequency is obtained, but exact frequency matching and phase matching are required
Solution Approach 1:
The patent creates a universal measurement system that does not require tuning to specific frequencies. By driving the Hall sensor at a known frequency θ and measuring at θ±ω, the system can measure magnetic fields at any frequency ω without requiring the drive frequency to match the magnetic field frequency, eliminating the need for frequency and phase matching
4Measurement precision
If frequency matching is required for accurate measurement, then measurement accuracy is improved, but the application range is limited
Solution Approach 1:
The patent changes the measurement parameter from direct frequency matching to frequency shifting. Instead of requiring the drive frequency to equal the magnetic field frequency, the system drives at frequency θ and measures at θ±ω. This parameter change allows accurate measurement of magnetic fields at any frequency while maintaining broad application range
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 allows for accurate and cost-effective measurement of magnetic fields at any frequency, reducing the need for complex circuitry and minimizing parasitic signals, enabling broader applications in fields like automotive engines, fusion reactors, and power electronics.
Implementation Method 1
Hall effect sensors for time-varying magnetic fields at unknown frequencies
Data Source
AI summary
We use the AC Hall effect to characterize a magnetic field at an unknown frequency (or frequencies). The current to the Hall sensor is driven at a known frequency f. The output Hall voltage is characterized in a frequency range from f1 to f2 (with f<f1<f2 and f2−f1<2f). This provides a measurement of the magnetic field in a frequency range from f1−f to f2−f. The resulting measurement of magnetic field spectral components is phase-independent and requires no prior knowledge of exact magnetic field frequency.