Distance Sensor with U-Shaped Magnet and Differential Readout
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing distance measuring devices face challenges in accurately measuring distance with high reliability due to interference from DC magnetic fields and limited signal excursion, which affects the precision and consistency of distance determination.
Innovation Solution
A distance measuring device is designed with two magnetic field sensors and a permanent magnet, where the sensors are arranged to detect changes in the magnetic flux, generating a difference signal that suppresses DC magnetic fields and enhances signal excursion, allowing for improved distance determination. The sensors are monolithically integrated with a semiconductor body and arranged to measure the magnetic field changes caused by a ferromagnetic encoding element, with the permanent magnet having a U-shaped design and recess to optimize the magnetic flux neutralization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single magnetic field sensor is used, then the device structure is simple, but DC magnetic field interference cannot be suppressed and measurement precision is reduced
Solution Approach 1:
The magnetic field sensing function is segmented into two separate sensors instead of using a single sensor. This segmentation allows the system to differentiate between DC magnetic field components and AC signal components, enabling suppression of DC interference while maintaining measurement precision.
Solution Approach 2:
A ferromagnetic encoding element is introduced as an intermediary between the permanent magnet and the magnetic field sensors. This encoding element modulates the magnetic field, creating detectable AC signals that carry distance information while allowing the system to reject DC magnetic field interference.
2Reliability
If magnetic field sensors are arranged to detect flux changes, then signal excursion is enhanced, but the magnetic-flux-free region must be neutralized requiring additional design
Solution Approach 1:
The permanent magnet is designed with an asymmetric U-shaped structure with a recess, creating an asymmetric magnetic field distribution. This asymmetry ensures that the magnetic flux lines are concentrated in specific regions, enhancing the magnetic-flux-free region neutralization effect and improving signal detection reliability.
Solution Approach 2:
The magnetic circuit is pre-configured with a permanent magnet and ferromagnetic encoding element to establish a controlled magnetic field environment before measurement begins. This preliminary arrangement ensures that the magnetic-flux-free region is properly neutralized, providing a stable baseline for accurate distance measurements.
3Measurement precision
If two magnetic field sensors are used with difference signal determination, then DC magnetic fields are suppressed, but device complexity increases
Solution Approach 1:
The outputs of two magnetic field sensors are combined through difference signal determination in the analysis circuit. This merging approach cancels out common-mode DC magnetic field interference while preserving the differential AC signal that contains distance information, achieving precision enhancement without excessive complexity.
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 solution effectively rejects DC magnetic fields, increases signal excursion, and enhances the reliability of distance determination by neutralizing the magnetic-flux-free region, leading to more precise and consistent measurements.
Implementation Method 1
a first magnetic field sensor, wherein the magnetic field sensor provides a first measurement signal as a function of the strength of the magnetic field
Implementation Method 2
the value of the output signal based on the neutralization of a magnetic-flux-free region is a function of a distance of a ferromagnetic encoding element from the two magnetic field sensors
Data Source
AI summary
A distance measuring device with two magnetic field sensors and a permanent magnet and a semiconductor body is provided. The device includes a monolithically integrated evaluation circuit, and a difference signal can be determined by means of the magnetic field sensors and provides an output signal as a result of the determination. The value of the output signal based on the neutralization of a magnetic-flux-free region is a function of a distance of a ferromagnetic sensing element from the two magnetic field sensors. The semiconductor body is arranged between U-shaped pole shanks of the magnet, which is magnetized in the X direction, wherein the first magnetic field sensor is arranged in an area located between two opposing shanks of the first pole, and the second magnetic field sensor is arranged in an area located between two opposing shanks of the second pole.