Magnetic Sensor Arrangement for Interference-Resistant Position Detection
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Solution Overview
Problem
Magnetic field sensors, particularly Hall sensors, are susceptible to interference from external magnetic fields, leading to undefined output signals when the magnetic field source is removed, as they rely on specific magnetic field strengths for end position detection.
Innovation Solution
A sensor arrangement comprising three magnetic field sensors arranged along a curved direction, with combination means and an evaluation unit to generate well-defined channel signals that compensate for interference, allowing for accurate end position detection even in the absence of the magnetic field source, by using differences and threshold comparisons to produce a clear output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetic field sensors are used for noncontact detection of positions and angles, then contactless measurement is achieved, but the sensors become susceptible to external magnetic field interference leading to undefined output signals
Solution Approach 1:
The measurement task is divided into two independent channels: a first channel for measuring the primary magnetic field component and a second channel for measuring interference fields. Each channel has its own combination means that processes signals from multiple magnetic field sensors (SM1, SM2, SM3) separately. This segmentation allows the evaluation unit to distinguish between useful measurement signals and interference, resolving the contradiction by enabling reliable output signal generation even in the presence of external magnetic field interference.
2Measurement precision
If end position detection is based on specific magnetic field strength thresholds, then position detection is achieved, but the detection becomes susceptible to interference fields that alter magnetic field strength
Solution Approach 1:
The evaluation unit acts as an intermediary that receives processed signals from both the first and second combination means. It compares the first channel signal (representing primary magnetic field) with the second channel signal (representing interference) and determines the end position based on their relationship rather than absolute threshold values. This intermediary processing eliminates susceptibility to interference fields while maintaining precise end position detection capability.
3Object-affected harmful factors
If multiple magnetic field sensors are combined to compensate for interference, then interference resistance is improved, but the device complexity increases
Solution Approach 1:
Multiple magnetic field sensors (SM1, SM2, SM3) are merged into two functional groups processed by first and second combination means. The first combination means combines signals for primary measurement, while the second combines signals for interference detection. This merging approach achieves interference compensation through signal combination rather than requiring completely separate sensor systems, thus improving interference resistance while controlling device complexity through functional integration.
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 sensor arrangement effectively reduces the impact of external interference, providing a well-defined output signal for determining the end position of a movable magnetic field source, ensuring accurate positioning regardless of alternating interference fields and the presence of the magnetic field source.
Implementation Method 1
Magnetic field sensors, particularly Hall sensors, are widely used for noncontact detection of positions and angles
Data Source
AI summary
A sensor arrangement comprises a first, a second and a third magnetic field sensor that are arranged along a curved principal direction. A first combination means is connected to the first and second magnetic field sensors and a first channel signal can be derived from the signals of the first and second magnetic field sensors by the first combination means. A second combination means is connected to the first, second and third magnetic field sensors (SM1, SWM2, SM3. A second channel signal is derived by the second combination means from signals of the first, second and third magnetic field sensors. An evaluation unit that is connected to the first and second combination means is set up to derive an end position of a magnetic source movable relative to the sensor arrangement as a function of the first and second channel signals.