Dual Hall Speed Sensor Magnetic Interference Compensation
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Solution Overview
Problem
Existing speed sensors, particularly those using Hall detectors, are susceptible to external disturbing magnetic fields, which can cause the magnetic field in the detector to be diminished or amplified, leading to inaccurate or missing digital signals, resulting in incorrect tachograph records.
Innovation Solution
A speed sensor design featuring two Hall sensors with basic magnets oriented in opposite directions, where one sensor's magnetic field is strengthened and the other's weakened by an external disturbing magnet, ensuring at least one sensor remains within its sensitivity range, producing accurate digital signals even in the presence of external magnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single Hall sensor is used for speed detection, then the device complexity is low, but the reliability deteriorates when exposed to external disturbing magnetic fields
Solution Approach 1:
The patent divides the single sensing function into two separate Hall sensors, each with its own basic magnet oriented in opposite directions. This segmentation allows the system to maintain low individual sensor complexity while achieving high overall reliability through redundancy and differential measurement, resolving the contradiction between simple structure and reliable operation in magnetic interference environments.
2Measurement precision
If the Hall detector is placed in close proximity of the gearwheel for accurate speed scanning, then the measurement precision is improved, but the susceptibility to external magnetic fields increases
Solution Approach 1:
The patent converts the harmful external magnetic field into a beneficial differential signal. By orienting the two basic magnets in opposite directions, the external field affects both sensors differently, creating a measurable difference that can be used to compensate for interference. This transforms the harmful magnetic interference into useful information for maintaining measurement precision.
3Device complexity
If threshold values for analog-to-digital conversion are fixed, then the device complexity is low, but the measurement precision deteriorates when magnetic field intensity varies
Solution Approach 1:
The patent implements dynamic threshold adjustment in the electronic circuit, where the threshold values for analog-to-digital conversion are automatically adapted to the actual magnetic field conditions. This dynamic adaptation maintains measurement precision across varying magnetic field intensities while keeping the circuit design practical and implementable.
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 dual Hall sensor arrangement prevents concurrent elimination of magnetic fields, allowing for continuous and accurate speed measurement of a gearwheel, even when exposed to external disturbing magnetic fields, thereby providing undistorted and exact information about the gearwheel's speed.
Implementation Method 1
speed sensors with Hall detectors are used. The Hall detector is placed in close proximity of the gearwheel periphery
Implementation Method 2
the magnetic lines of force of the basic magnet of the Hall sensor are concentrated in the Hall detector center causing thus the increase in the Hall detector output voltage
Data Source
AI summary
A speed sensor (1) including a first magnetic sensor (3) with a first magnetic detector (30), which is connected to an electronic circuit for conversion of its output analog signal to a first digital signal and a second magnetic sensor (4) with a second magnetic detector (40), which is also connected to an electronic circuit for conversion of its output analog signal to a second digital signal.