Open Loop MR Sensor In-Situ Normalization
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Solution Overview
Problem
Magnetic field sensors, particularly magneto-resistive (MR) sensors, face accuracy degradation due to long-term resistance shifts caused by thermal, electrical, and mechanical stresses, which affect the accuracy of open-loop magnetic field sensing applications.
Innovation Solution
The implementation of in-situ normalization methods using a magnetic field generation coil to place the MR sensor in a determined state, such as saturation, allowing for the calculation and application of normalizing factors to correct resistance shifts, and the use of a reference sensor to minimize errors and enhance sensitivity calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If open-loop MR sensing is used to achieve higher sensitivity compared to Hall sensors, then sensitivity is improved, but measurement accuracy deteriorates due to resistance shifts during operation
Solution Approach 1:
The patent applies preliminary action by performing normalization of the MR sensor output using stored maximum and minimum resistance values before using the sensor for measurement. This pre-processing step establishes a reference range that compensates for resistance shifts, allowing the sensor to maintain both high sensitivity and accurate measurements throughout its operational life.
2Device complexity
If open-loop configuration is used to simplify the sensing circuit, then device complexity is reduced, but measurement accuracy deteriorates due to sensitivity to absolute resistance fluctuations
Solution Approach 1:
The patent implements self-service by having the MR sensor automatically normalize its own output using internally stored maximum and minimum resistance values. This eliminates the need for external reference sensors or complex compensation circuits, maintaining circuit simplicity while significantly improving measurement accuracy through the self-normalization process.
3Duration of action of stationary object
If long-term operation is performed to achieve sustained sensing, then duration of action is extended, but measurement accuracy deteriorates due to resistance shifts from thermal, electrical and mechanical stresses
Solution Approach 1:
The patent stores the maximum and minimum resistance values of the MR sensor during manufacturing or initial calibration before long-term operation begins. These pre-stored reference values enable continuous normalization throughout the sensor's operational life, compensating for resistance drift caused by thermal, electrical, and mechanical stresses and maintaining measurement accuracy over extended periods.
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 significantly reduces measurement errors caused by resistance shifts, enabling accurate open-loop MR sensing by normalizing sensor outputs and improving sensitivity accuracy over time, even under stress conditions.
Implementation Method 1
a magnetic field generation coil to place the MR sensor in a determined state, such as saturation
Implementation Method 2
magneto-resistive (MR) sensors, the field value is derived directly from the MR sensor's resistance
Data Source
AI summary
An apparatus and a general method to measure a magnetic field using magneto-resistive sensors in an open-loop configuration are disclosed. A key feature is the regular in-situ normalization of the sensors to compensate for the effects of sensor aging.