Magnetic Field Sensor Self-Test via Switching Circuit
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Solution Overview
Problem
Conventional magnetic field sensors lack built-in self-test capabilities to effectively test the magnetic field sensing elements and all circuits within the sensor, especially in the presence of varying external magnetic fields.
Innovation Solution
The implementation of a magnetic field sensor with at least two magnetic field sensing elements and a switching circuit that can configure these elements into normal and diagnostic modes, allowing for self-testing regardless of the external magnetic field magnitude, by generating distinct signal portions responsive to measured and diagnostic magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional built-in self-test circuits are used in magnetic field sensors, then the self-test function can be activated, but the magnetic field sensing element and all circuits within the sensor cannot be effectively tested
Solution Approach 1:
The magnetic field sensor is divided into multiple sensing elements that can be independently configured. During diagnostic mode, these elements are arranged in a specific configuration that enables self-testing of individual elements and circuits, while during normal operation, they are arranged in a different configuration for standard sensing functionality.
Solution Approach 2:
The circuit configuration of the magnetic field sensing elements is made dynamic through switching circuitry. The elements can be switched between a normal mode configuration for regular operation and a diagnostic mode configuration for self-testing, allowing the same hardware to serve multiple functions based on operational requirements.
2Productivity
If magnetic field sensors operate in normal mode, then they can sense external magnetic fields, but they cannot perform self-testing regardless of external magnetic field magnitude
Solution Approach 1:
The magnetic field sensor alternates between normal sensing operation and diagnostic self-testing modes through periodic switching. During normal operation, the sensing elements are configured for external field detection. At diagnostic intervals, the switching circuit reconfigures the elements into diagnostic mode to perform self-testing, then returns to normal mode for continued sensing functionality.
3Device complexity
If a single magnetic field sensing element is used, then the circuit is simple, but comprehensive self-testing of all circuits cannot be performed
Solution Approach 1:
Multiple magnetic field sensing elements serve dual purposes: during normal operation, they function as sensing elements for detecting external magnetic fields, and during diagnostic mode, they are reconfigured to function as test signal generators and test subjects for comprehensive self-testing of all circuits including the sensing elements themselves.
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
Enables comprehensive self-testing of magnetic field sensors, ensuring functionality and sensitivity measurement or calibration, regardless of the external magnetic field strength, thereby enhancing reliability and maintenance capabilities.
Implementation Method 1
Hall effect elements generate an output voltage proportional to a magnetic field
Implementation Method 2
magnetoresistance elements change resistance in proportion to a magnetic field
Data Source
Figure 1~1A
Figure 2
Figure 2A~2C
AI summary
A magnetic field sensor includes a diagnostic circuit that allows a self-test of most of, or all of, the circuitry of the magnetic field sensor, including a self-test of a magnetic field sensing element used within the magnetic field sensor. The magnetic field sensor can generate a diagnostic magnetic field to which the magnetic field sensor is responsive.