Pulse-Induction Coil Layout for Stray Magnetic Field Rejection
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Solution Overview
Problem
Pulse-induction displacement transducers are vulnerable to adverse effects from stray alternating or changing magnetic fields, leading to false readings, particularly in applications like automotive systems where dynamo or electric motor-generated fields interfere with the sensor's accuracy.
Innovation Solution
The transducer design features two coil parts wound in opposite senses, connected in series, with pulse induction circuitry between their terminals, and a target covering both parts to cancel out the impact of stray magnetic fields by inducing opposite voltages, thus reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single coil component is used in the pulse-induction displacement transducer, then the device complexity is reduced, but the transducer becomes vulnerable to stray alternating magnetic fields causing false readings
Solution Approach 1:
The coil component is segmented into two separate coil parts (first coil part and second coil part) wound in opposite senses. Each coil part is exposed to the target, and their opposing wound configurations cause them to respond differently to stray magnetic fields versus target-induced fields, enabling discrimination between interference and valid signals
Solution Approach 2:
The two coil parts are given different local qualities by winding them in opposite senses (directions). This creates asymmetry in their response to magnetic fields: when exposed to the same stray alternating magnetic field, they generate opposing voltages that cancel each other, while their response to the target remains differential and detectable
2Reliability
If two coil parts wound in opposite senses are used, then the transducer reliability against magnetic interference is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The coil is divided into two distinct coil parts that can be manufactured and assembled separately. This segmentation allows for standardized manufacturing processes for each part while maintaining the overall functional requirement of opposite winding senses, making the precision requirement manageable through modular production
Solution Approach 2:
The intentional asymmetric winding (opposite senses) is designed into the system as a functional feature rather than a precision constraint. The asymmetry is what enables the interference rejection mechanism, and the system is designed to accommodate this asymmetry rather than require perfect symmetry, thereby reducing the actual precision burden
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
This configuration substantially cancels the effect of stray magnetic fields, ensuring accurate measurements by maintaining consistent exposure of both coil parts to the target, thereby minimizing interference and maintaining sensor reliability.
Implementation Method 1
cause a pulse of electrical current to pass through the at least one coil component
Implementation Method 2
measure the electrical current passing through the at least one coil component, or a voltage across it, at a time when any electrical current through or voltage across the at least one coil component would have died away in the absence of a target
Data Source
AI summary
A pulse-induction displacement transducer comprising at least one coil component (100,150), at least one target (112,174), and pulse induction circuitry (102,152} constructed and arranged to cause a pulse of electrical current to pass through the said at least one coil component (100,150). The pulse ends abruptly. Subsequently, the electrical current passing through the said at least one coil component (100,150), or the voltage across it, is measured at a time when any electrical current through or voltage across the said at least one coil component (100, 150) would have died away in. the absence of a target. This provides an indication of the relative position between the target (112,174) and the said at least one coil component (100, 150). The said at least one coil component (100,150) comprises a first terminal portion (108,158), a first coil part (104,152) connected directly or indirectly to the said first terminal portion (108,158) and wound in one sense. The coil component (100,150) also comprises, in series with the said first coil part (104, 152), a second coil part (164) wound in the opposite sense. The said second coil part (106,164) is connected directly or indirectly to a second terminal portion (110, 168). The said pulse induction circuitry (102,152) is connected between the said first terminal portion (108,158) and the said second terminal portion (110,168).