Magnetic Field Sensor with Frequency Modulated Reference
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Solution Overview
Problem
Magnetic field sensors face challenges in maintaining accuracy over time due to mechanical and thermal stress, limited measurement bandwidth, especially for high-frequency currents, and difficulties in separating reference signals from measurement signals effectively.
Innovation Solution
A magnetic field sensor system that includes a reference magnetic field generator, a magnetic field sensing cell, and a signal processing circuit with feedback loops, utilizing frequency modulation and demodulation to separate and correct for error fluctuations, allowing for accurate measurement of external magnetic fields across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If factory calibration is used to compensate for voltage offset and temperature drift, then initial accuracy is improved, but accuracy deteriorates over time due to mechanical stress and ageing
Solution Approach 1:
The patent implements a feedback mechanism where the sensor continuously measures a known reference magnetic field and compares it against the expected value. The difference (error signal) is fed back to a correction circuit that adjusts the sensor output in real-time, compensating for drift caused by mechanical stress, ageing, and temperature changes. This closed-loop feedback ensures long-term accuracy maintenance.
Solution Approach 2:
The patent performs preliminary calibration by having the sensor measure a known reference magnetic field before actual measurements. This preliminary action establishes a baseline that is then used to detect and correct for subsequent drift, allowing the system to compensate for ageing and stress effects proactively rather than reactively.
2Device complexity
If reference signal is incorporated in measurement signal output, then signal processing is simplified, but signal pollution occurs reducing measurement accuracy
Solution Approach 1:
The patent segments the signal processing into distinct phases: a first phase where the sensor measures both the external magnetic field and the reference magnetic field, and a second phase where the reference measurement is used to correct the external field measurement. This temporal segmentation allows the reference signal to be separated from the measurement signal, preventing pollution while maintaining processing simplicity.
Solution Approach 2:
The patent uses the reference magnetic field measurement as an intermediary to indirectly correct the external field measurement. Instead of directly eliminating the reference signal from the output, the system uses the reference measurement as a mediator to calculate correction factors that are then applied to the external field signal, achieving signal separation without complex processing.
3Measurement precision
If separate Hall cells with reference coils are provided, then reference signal separation is improved, but device complexity and temperature sensitivity increase
Solution Approach 1:
The patent merges the reference magnetic field generation and measurement functions into a single integrated system. The same magnetic field sensor that measures the external field also measures the reference field generated by onboard coils, eliminating the need for separate Hall cells and reference coils. This integration reduces device complexity while maintaining reference signal separation capability through software-based correction algorithms.
4Measurement precision
If sensor is designed for low frequency measurement, then accuracy is improved, but measurement bandwidth is limited preventing high frequency current measurement
Solution Approach 1:
The patent implements dynamic correction algorithms that adapt to different measurement frequencies. The feedback mechanism continuously adjusts the correction factors based on the actual measurement conditions, allowing the sensor to maintain accuracy across a wide frequency range from DC to 100 kHz. This dynamic adaptation enables the sensor to transition smoothly between low-frequency and high-frequency operation without sacrificing precision.
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 system ensures reliable and accurate measurement of electrical currents over a large frequency bandwidth (0 to 100 kHz), effectively compensating for mechanical and thermal stress, and simplifies the separation of reference signals, enhancing the sensor's stability and responsiveness.
Implementation Method 1
a magnetic field sensing cell (6) including a magnetic field sensing element
Implementation Method 2
a reference magnetic field generator (8)
Data Source
AI summary
A magnetic field sensor comprises a reference magnetic field generator (8), a magnetic field sensing cell (6) including Hall effect sensing elements (12), and a signal processing circuit (4) connected to the output (11) of the magnetic field sensing cell and comprising one or more feedback lines (27, 28) for correcting error fluctuations in the transfer characteristic of the magnetic field sensor. The reference magnetic field generator is adapted to generate a frequency modulated reference magnetic field. The signal processing circuit further includes a modulator connected to the magnetic field sensing cell, adapted to modulate the output signal thereof at a frequency different from the modulation frequency of the reference magnetic field generator.