Inductive Rotational Speed Sensor Using PCB Traces
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Solution Overview
Problem
Conventional rotational speed measurement systems are often expensive, bulky, and prone to noise and interference, lacking the accuracy and digital signal robustness needed for harsh environments, and require complex setups for advanced networking and wireless communication.
Innovation Solution
An inductive rotational speed sensor assembly with non-axisymmetric receiver windings and additional poles on printed circuit boards (PCBs) for enhanced precision, using electromagnetic coupling to generate a robust signal, and a method to calculate rotational speed from signal peaks, incorporating filters, amplifiers, and pulse counting circuits for accurate output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional contactless electromagnetic wound coils or magnet systems are used for rotational speed measurement, then non-contact measurement is achieved, but the device becomes bulky, heavy, and expensive
Solution Approach 1:
The patent replaces heavy mechanical electromagnetic wound coils with planar printed circuit board traces that generate electromagnetic fields inductively. This substitution maintains the contactless measurement capability while dramatically reducing the weight and bulk of the sensor assembly by using thin PCB traces instead of traditional wound coil structures.
Solution Approach 2:
The patent changes the physical form and electrical characteristics of the sensing coils from three-dimensional wound coils to two-dimensional planar PCB traces. This parameter change in coil geometry and construction method enables contactless measurement with significantly reduced weight and improved integration while maintaining the necessary electromagnetic coupling for speed detection.
2Reliability
If conventional electromagnetic wound coils or magnet systems are used, then non-contact measurement is achieved, but the device size increases
Solution Approach 1:
The patent replaces bulky mechanical electromagnetic wound coils with compact planar PCB trace structures. This substitution achieves the same contactless measurement function while occupying minimal space, as the sensing elements are integrated directly into the PCB plane rather than requiring external coil assemblies.
Solution Approach 2:
The patent merges the sensing coil structure with the PCB substrate itself, integrating the electromagnetic sensing function directly into the circuit board. This merging eliminates the need for separate coil assemblies and reduces the overall sensor footprint while maintaining contactless measurement capability.
3Reliability
If conventional sensors are used in harsh environments with mechanical vibrations and variable temperatures, then measurement is possible, but noise and signal interference increase
Solution Approach 1:
The patent replaces mechanical contact-based sensors with inductive PCB-based sensing that has no moving parts or physical contact points. This substitution eliminates friction, wear, and mechanical noise while the planar trace structure provides inherent stability against thermal expansion and vibration, reducing noise and interference in harsh environments.
Solution Approach 2:
The patent employs digital signal processing and microcontroller-based compensation that automatically adapt to environmental conditions. The system self-corrects for temperature variations and vibration effects through embedded algorithms, maintaining measurement accuracy without external intervention or additional shielding components.
4Measurement precision
If analog signals are used for rotational speed measurement, then measurement is achieved, but the system is sensitive to electromagnetic interference
Solution Approach 1:
The patent replaces analog signal transmission with digital signal processing throughout the measurement system. The microcontroller converts raw sensor data into digital readings and communicates rotational speed information digitally, providing immunity to electromagnetic interference that plagues analog systems while maintaining precise measurement capability.
Solution Approach 2:
The patent implements digital signal processing with filtering and compensation algorithms that continuously monitor and correct for interference. The microcontroller processes signals with digital filters that reject noise and interference, providing stable accurate measurements even in electrically noisy environments where analog systems would fail.
5Measurement precision
If traditional sensor systems are used, then rotational speed measurement is achieved, but cost increases
Solution Approach 1:
The patent replaces expensive precision mechanical sensors and wound coil assemblies with standard PCB manufacturing processes. The sensing elements are created using conventional PCB trace deposition techniques, eliminating the need for specialized coil winding equipment and precision mechanical assembly, thereby significantly reducing manufacturing cost while maintaining measurement precision.
Solution Approach 2:
The patent designs a multi-functional integrated circuit board that combines sensing, signal processing, filtering, and communication functions in a single PCB assembly. This universal design eliminates the need for multiple separate components and assemblies, reducing both material costs and manufacturing complexity while providing precise rotational speed measurement.
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 provides a cost-effective, compact, and accurate rotational speed measurement with improved linearity and resistance to noise and electromagnetic interference, enabling efficient digital signal communication.
Implementation Method 1
A high frequency alternating current input signal is applied to a transmitter coil to generate an alternating magnetic field
Implementation Method 2
The alternating magnetic field couples to a resonant target coil which in turn couples back to a receiver coil
Data Source
Figure 1
Figure 2A~2D
AI summary
An inductive rotational speed sensor assembly (100) includes a first PCB (10) with a transmitter coil (12) configured to convert an alternating electrical input into an alternating magnetic field. A second PCB (20) is operatively connected to the first PCB for relative rotation and includes a resonance coil (25; 25, 25A) in combination with a capacitor configured to couple to the alternating magnetic field of the first PCB to output a modulating position signal. The first PCB includes a receiver coil (15; 15, 15A) configured to receive the first and the modulating position signal and to output a signal indicative of rotational speed of the second PCB relative to the first PCB, derived from the frequency or time separation between pulses in the received signal indicating a high coupling between transmitter and receiver coil.