Magnetic Field Sensor Offset Compensation via Secondary Magnet
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Solution Overview
Problem
Existing magnetic field sensing systems are not suitable for harsh environments, such as automobiles, due to a decrease in magnetic field strength caused by protective overmolding, which affects the accuracy of magnetic field measurements.
Innovation Solution
A measuring system comprising a magnetic device with two permanent magnetic poles, where a secondary magnetic field partially compensates the main magnetic field, allowing for a reduced magnetic flux density in specific regions to enhance the signal-to-offset ratio and improve measurement accuracy, particularly in the presence of an encoder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective overmold is added to enclose the sensing element, then reliability in harsh environments is improved, but magnetic field strength decreases
Solution Approach 1:
The sensing element is extracted from the encapsulated package and mounted directly on the circuit board, eliminating the need for protective overmolding while maintaining reliability through direct mounting protection
Solution Approach 2:
The magnetic field sensor is divided into separate components (sensing element, magnet, circuit board mounting) rather than being enclosed in a single package, allowing the sensing element to be positioned close to the magnet without protective packaging interference
2Strength
If the sensing element is positioned closer to the magnet, then magnetic field strength is improved, but manufacturing complexity increases
Solution Approach 1:
The sensing element and magnet are merged into a single integrated component mounted on the circuit board, eliminating the need for precise positioning between separate encapsulated units while maintaining close proximity for strong magnetic field detection
3Ease of manufacture
If encapsulated magnetic field sensors are used, then ease of manufacture is improved, but measurement precision in harsh environments deteriorates
Solution Approach 1:
The sensing element is extracted from the encapsulated package that limits magnetic field strength, and mounted directly on the circuit board where it can operate in harsh environments without the restrictive packaging, thereby improving measurement precision while maintaining ease of manufacture through simple mounting procedures
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 system achieves a significant increase in signal-to-offset ratio with a cost-effective design, enabling accurate magnetic field detection even in harsh environments by reducing magnetic flux density in certain areas, thereby enhancing measurement precision.
Implementation Method 1
The magnetic field is formed by superimposing the main magnetic field and the secondary magnetic field, whereby the secondary magnetic field at least partially compensates the main magnetic field in the first spatial direction
Implementation Method 2
at least one magnetic field sensor for detecting a flux density of the magnetic field at least in a first spatial direction
Data Source
AI summary
A measuring system having a magnetic device for generating a magnetic field and at least one magnetic field sensor for detecting a flux density of the magnetic field, at least in a first spatial direction. The magnetic device has a top side facing the magnetic field sensor, the magnetic field sensor is spaced apart from the top side of the magnetic device, the magnetic device has a main magnet, having two poles, with a main magnetizing direction for generating a main magnetic field and at least one secondary magnet, having two poles, with a secondary magnetization direction for generating a secondary magnetic field, the main magnet has larger dimensions than the at least one secondary magnet, the magnetic field is formed by superposition of the main magnetic field and the secondary magnetic field, the secondary magnetic field at least partially compensates the main magnetic field in the first spatial direction.