Bifilar Wound Speed Sensor for Signal Matching
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Solution Overview
Problem
Existing magnetic sensors with multiple output channels for measuring rotational speed, such as in gas turbine engines, face challenges in achieving equal signal magnitudes due to varying rates of magnetic flux change, making it difficult to ensure detection consistency across channels, especially when one channel fails.
Innovation Solution
The magnetic sensor design features primary output circuits wound around each other, ensuring each experiences the same change in magnetic flux, resulting in identical induced voltages across channels, which are electrically independent and insulated from each other.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If primary windings are positioned at different physical locations around the pole piece, then the sensor can detect magnetic flux changes, but each channel produces different signal magnitudes requiring complex adjustment
Solution Approach 1:
The patent combines multiple primary windings into a single bifilar coil structure where two coils are wound together in parallel around the pole piece. This merging approach ensures both channels experience identical magnetic flux changes, producing equal signal magnitudes without requiring complex individual positioning or adjustment mechanisms.
Solution Approach 2:
The patent applies local quality by ensuring the bifilar coil structure provides uniform magnetic field exposure to both windings at the same location. The close spacing and parallel winding arrangement create locally identical magnetic coupling conditions, guaranteeing equal signal output from both channels.
2Manufacturing precision
If the number of turns on primary coils is varied to balance outputs, then signal magnitudes can be equalized, but the process becomes time-consuming and difficult to manufacture
Solution Approach 1:
The patent merges the winding process into a single bifilar operation where two coils are wound simultaneously in parallel. This eliminates the need for separate winding and adjustment operations for each channel, significantly simplifying manufacturing while ensuring precise signal matching through identical winding conditions.
Solution Approach 2:
The bifilar structure creates identical copies of the winding pattern for both channels. By winding both coils together in the same passes, the patent ensures exact replication of turn count and positioning, guaranteeing equal signal magnitudes without requiring manual adjustment or measurement.
3Ease of manufacture
If bifilar coil arrangement is used, then manufacturing is simplified, but coils may not pick up exactly the same magnetic field if spaced apart
Solution Approach 1:
The patent merges the two coils into a tightly bound bifilar structure where the coils are wound adjacent to each other around the pole piece. This close coupling ensures both windings experience the same magnetic flux density, eliminating signal magnitude differences while maintaining manufacturing simplicity.
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 approach simplifies manufacturing and replication, providing consistent signal magnitudes across channels, reducing the complexity and time required for adjustment and positioning, and enhancing the reliability of sensor redundancy.
Implementation Method 1
a coil forming part of an electric circuit is wound around a magnetically energised pole piece. A voltage is induced in the coil by changes in the magnetic flux pattern associated with the pole piece, caused by the relative movement of a projection made of magnetic material in the proximity of the pole piece.
Data Source
AI summary
A probe for sensing the movement of a body of magnetic material comprises a magnetically energisable pole piece and a plurality of electrically conductive circuits, coupled to the magnetic pole piece, such that a change in magnetic flux in the pole piece caused by movement of the body relative to the pole piece induces a voltage in each of the circuits. The electrically conductive circuits are wound around in a symmetrical fashion each other such that in the vicinity of the magnetic pole piece each circuit experiences substantially the same change in magnetic flux. A probe of this type provides a plurality of substantially identical output signals and is easy to manufacture and replicate.