Magnetic Field Sensor Axial Position Detection
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Solution Overview
Problem
Conventional magnetic field sensors, such as gear tooth sensors, do not provide an output signal representative of the relative location of the sensor and a target object in an axial direction along a movement line, and they fail to distinguish this location when the target object is spinning or stationary.
Innovation Solution
A magnetic field sensor system that includes a magnet generating a DC magnetic field and two magnetic field sensing elements positioned near ferromagnetic surfaces on a target object, generating electronic signals whose difference in amplitude indicates the relative location of the sensor and the target object along a movement axis, while being insensitive to the target object's rotation, using a differential amplifier and optional linearization and clamping modules to process these signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetic field sensors are used to detect gear tooth movement, then rotation speed and absolute angle can be sensed, but the relative location of the sensor and target object along the movement line cannot be provided
Solution Approach 1:
The sensor divides the detection function into multiple magnetic field sensing elements (first and second elements) positioned at different locations. Each element detects magnetic field variations independently, and their combined outputs provide both rotational information and axial position information, enabling precise relative location measurement without increasing overall device complexity
Solution Approach 2:
The invention extends the sensing capability from purely rotational detection to three-dimensional detection by adding axial position sensing along the movement line. The differential arrangement of sensing elements in space enables the sensor to detect variations in both rotational angle and axial position simultaneously, providing comprehensive relative location information
2Adaptability or versatility
If conventional magnetic field sensors detect target object movement, then rotation information can be provided, but the sensor cannot distinguish relative location when the target object is spinning or stationary
Solution Approach 1:
The sensor is designed to perform multiple detection functions simultaneously: it can detect rotational movement, axial position, and maintain accuracy regardless of whether the target object is spinning or stationary. The differential amplifier circuit processes signals from multiple sensing elements to provide universal detection capability across different operational states
Solution Approach 2:
The sensor system uses feedback through the differential amplifier to compare signals from multiple magnetic field sensing elements. This feedback mechanism enables the system to distinguish between rotational movement and axial position changes, maintaining measurement precision regardless of the target object's spin status by continuously adjusting based on the differential signal
3Object-affected harmful factors
If differential amplifier is used to process sensor signals, then noise rejection is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple magnetic field sensing elements and their signal processing into a single integrated differential amplifier circuit. This merging approach allows noise rejection functionality to be implemented efficiently without proportionally increasing device complexity, as the differential arrangement naturally rejects common-mode electrical noise while processing signals from multiple sensors
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 the generation of an output signal representative of the relative location of the magnetic field sensor and the target object in both linear and rotational movements, providing accurate positioning information regardless of the target object's spin status, with improved noise rejection and signal linearity.
Implementation Method 1
a magnet operable to generate a DC magnetic field
Implementation Method 2
first and second magnetic field sensing elements operable to sense first and second influenced magnetic fields, respectively, related to the DC magnetic field but influenced by at least one ferromagnetic surface
Implementation Method 3
Magnetic field sensors generally include a magnetic field sensing element and other electronic components
Implementation Method 4
influenced by at least one ferromagnetic surface upon a ferromagnetic target object
Data Source
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AI summary
A magnetic field sensor with a magnet is disposed proximate to a ferromagnetic target object having at least one ferromagnetic surface. The magnetic field sensor is operable to sense a relative location between the magnetic field sensor and the ferromagnetic target object along a movement line. In some embodiments, the target object is also spinning about a rotation axis parallel to the movement line. A corresponding method is described.