Magnetic Field Sensor Differential Measurement
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Solution Overview
Problem
Existing magnetic field measuring devices are limited in accurately detecting asymmetrical z-components of magnetic fields due to interference from magnetic DC fields and lack of sensitivity to z-direction components, particularly when the magnetic field is not aligned with the sensors.
Innovation Solution
A magnetic field measuring device with two orthogonally arranged Hall sensors and a magnet, where the sensors are spaced apart in the x-z plane and a ferromagnetic body is used to deflect magnetic field lines, allowing differential measurement of z-component signals, thereby enhancing sensitivity and reducing DC field interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single Hall sensor is used to measure magnetic field components, then the device structure is simple, but the sensitivity to z-direction magnetic field components and the ability to detect asymmetrical fields is insufficient
Solution Approach 1:
The measurement function is segmented into two separate Hall sensors positioned at different locations in the x-z plane. Each sensor measures the magnetic field at its specific position, and the differential measurement of these two sensors enables detection of z-component variations that would be invisible to a single sensor, thereby improving measurement precision without requiring each individual sensor to be more complex
Solution Approach 2:
A ferromagnetic body is introduced as an intermediary element to deflect magnetic field lines. This ferromagnetic body modifies the magnetic field distribution in the z-direction, creating asymmetrical field patterns that the two Hall sensors can detect differentially. The ferromagnetic body acts as a mediator that translates z-direction field variations into measurable signal differences between the two sensors
2Measurement precision
If magnetic field sensors are arranged symmetrically with respect to the magnet, then the device structure is balanced and simple, but the ability to detect asymmetrical z-components of magnetic field is reduced
Solution Approach 1:
The two Hall sensors are deliberately positioned asymmetrically with respect to the magnet's symmetry plane, both in terms of their separation distance and their offset from the symmetry plane. This asymmetric arrangement ensures that when a ferromagnetic body deflects magnetic field lines in the z-direction, the two sensors experience different field strengths, creating a measurable differential signal that directly corresponds to the asymmetrical z-component of the magnetic field
3Measurement precision
If the magnetic field lines are parallel to the x-y plane, then the sensors can easily measure x and y components, but the z-component of the magnetic field cannot be detected
Solution Approach 1:
The ferromagnetic body serves as a mediator that transforms the magnetic field configuration. By placing this ferromagnetic body at different positions in the z-direction, the magnetic field lines are deflected to pass through the ferromagnetic body and emerge with z-direction components. This allows the Hall sensors, which are sensitive to z-components, to detect field variations that would otherwise be purely in the x-y plane
Solution Approach 2:
The position of the ferromagnetic body in the z-direction is varied to modulate the magnetic field. As the ferromagnetic body moves closer to or farther from the Hall sensors, it changes the degree of magnetic field line deflection, thereby changing the z-component of the magnetic field at the sensor locations. This parameter change enables dynamic control of the z-component signal for detection purposes
4Measurement precision
If DC magnetic fields are present in the measurement environment, then the overall magnetic field strength increases, but the measurement accuracy is reduced due to DC offsets
Solution Approach 1:
The differential measurement approach extracts and isolates the AC signal component (variations in z-component magnetic field) from the DC background field. By subtracting the signals from two symmetrically positioned sensors, the common-mode DC offset is rejected, and only the differential AC signal corresponding to the modulated z-component remains, thereby extracting the useful information while eliminating the harmful DC interference
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 device effectively doubles signal deviation by differentially measuring magnetic field components, suppressing DC field offsets and improving detection of asymmetrical z-components, with increased sensitivity and accuracy.
Implementation Method 1
the magnetic field sensors each have a z - measure components of a magnetic field
Implementation Method 2
the magnetic field of the first magnet must be modulated by means of a ferromagnetic body in such a way that the magnetic field lines of the magnet are deflected from the rest position in the x-y plane at least partially and differently in the z-direction at both magnetic field sensors
Data Source
Figure 1~4
Figure 5~6
AI summary
A magnetic field measuring device comprising a first semiconductor body with a surface formed in a first xy plane, wherein the first semiconductor body has two spaced-apart magnetic field sensors arranged along a first connecting line on its surface, and wherein the magnetic field sensors each measure a z-component of a magnetic field, and the x-direction and the y-direction and the z-direction are each orthogonal to each other, and further comprising a first magnet with a planar principal extensional surface formed in a second xy plane and with a symmetry surface formed in an xz plane, wherein the direction of magnetization is substantially or exactly parallel to the principal extensional surface and substantially or exactly parallel to the symmetry surface, and the first semiconductor body and the first magnet are rigidly fixed to each other.and the first semiconductor body is arranged translationally offset from the first magnet in the xy-plane, wherein an offset formed in the z-direction between the first xy-plane and the second xy-plane is smaller than a thickness formed in the z-direction of the first magnet, and wherein both magnetic field sensors are spaced apart from each other in the xz-plane and are arranged in the xz-plane along the extent of the north pole or along the extent of the south pole, and wherein, in the case of a z-component of the magnetic field of the first magnet that is asymmetric with respect to the symmetry surface, the magnetic field sensors form different signals with respect to each other in order to measure the signals differentially.