Magnetoresistive Sensor Autocalibration for Drift Compensation
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Solution Overview
Problem
Magnetoresistive sensors experience reliability and accuracy issues due to temperature drift, aging, and hysteresis, leading to inconsistent magnetic field measurements, which existing compensation methods fail to fully address.
Innovation Solution
A method involving additional magnetic field pulses to saturate and unsaturate the sensor, allowing for the measurement of resistance extremes, followed by autocalibration to determine a corrected resistance value for accurate magnetic field measurement, compatible with existing signal-processing and bridge-circuit techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional magnetoresistive sensors are used for magnetic field measurements, then the sensors can detect magnetic fields, but the measurements are affected by drift due to temperature, aging, and irradiation leading to inaccurate and unreliable results
Solution Approach 1:
The patent applies preliminary action by performing autocalibration before each measurement sequence. The sensor is subjected to saturation pulses of known strength and polarity to establish reference resistance values (Rmax and Rmin) before measuring the external magnetic field. This preliminary calibration action compensates for drift effects from temperature, aging, and irradiation, ensuring accurate measurements throughout the measurement process.
Solution Approach 2:
The patent implements feedback through the autocalibration process where the sensor's resistance response to known saturation pulses is used to determine correction factors. The measured resistance during calibration is fed back to calculate the sensor's current sensitivity and offset, which are then used to correct subsequent measurements, continuously maintaining measurement accuracy despite environmental drift.
2Measurement precision
If negative feedback is applied to compensate for sensitivity drift, then the magnetic field sensitivity coefficient can be stabilized, but the electricity consumption increases significantly
Solution Approach 1:
The patent applies periodic action by performing autocalibration only at specific intervals before measurement sequences rather than continuously applying feedback. The sensor is saturated with calibration pulses periodically to update reference values, which then remain valid for the subsequent measurement period. This periodic approach maintains sensitivity stability while dramatically reducing energy consumption compared to continuous feedback mechanisms.
3Measurement precision
If magnetoresistive elements are used to measure magnetic fields, then the resistance varies with the applied magnetic field, but hysteresis effects disturb the quality of measurements
Solution Approach 1:
The patent eliminates hysteresis effects by applying preliminary saturation pulses of both positive and negative polarity before measurement. These pulses drive the sensor into full saturation, resetting the magnetic state to a known condition. By performing this preliminary action, the sensor's hysteresis loop is effectively closed, and the sensor starts from a standardized state, ensuring consistent and reliable measurements regardless of previous measurement history.
4Temperature
If bridge circuits with multiple similar elements are used to compensate for thermal drift, then some thermal drift can be compensated, but the magnetic field sensitivity coefficient still drifts due to finite Curie temperature
Solution Approach 1:
The patent overcomes the limitations of bridge circuits by implementing active feedback through autocalibration. Instead of passively compensating for thermal drift using multiple similar elements, the system actively measures the sensor's actual response to known saturation pulses and uses this feedback to calculate correction factors. This feedback mechanism compensates for both thermal drift and sensitivity coefficient drift caused by finite Curie temperature, achieving superior measurement 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
This approach systematically corrects sensor sensitivity drift, eliminates hysteresis effects, and provides a reliable method for accurate magnetic field measurements by using the resistance extremes to determine a corrected resistance value, enhancing measurement reliability and accuracy.
Implementation Method 1
the electrical resistance of the material constituting the magnetoresistance is modified in the presence of a magnetic field
Implementation Method 2
applying in situ, prior to each measurement of the external magnetic field, at least one additional magnetic field pulse in the space containing the magneto-resistive sensor, which additional magnetic field pulse presents a first value having a first polarity that is positive or negative and a magnitude that is sufficient to saturate the sensor
Data Source
AI summary
The device for measuring magnetic field by using a magnetoresistive sensor comprises at least one magnetoresistive sensor (5), a module (50) for measuring the resistance of the magnetoresistive sensor (5), a generator module (40, 6) for generating an additional magnetic field in the space containing the magnetoresistive sensor (5), and a control unit (60) firstly for selectively controlling the generator module (40, 6) to apply an additional magnetic field pulse possessing a first value with first polarity that is positive or negative and magnitude that is sufficient to saturate the magnetoresistive sensor (5), and secondly for selectively controlling measurement of the resistance of the magnetoresistive sensor (5) by the module (50) for measuring resistance.