Helical Slow-Wave Position Sensor for Harsh Environments
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Solution Overview
Problem
Existing position sensors face challenges with low accuracy, sensitivity, and resolution at low frequencies, and require complex and costly electronic circuitry, making them unsuitable for harsh environments and high-reliability applications.
Innovation Solution
A sensing apparatus using a coupled slow-wave structure with impedance conductors curled into helices or spirals, connected by coaxial cables to a remote electronics module, allowing the sensing element to operate in harsh environments while keeping the electronics module separate and reducing the need for complex circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electronic circuits are integrated close to the sensing element, then signal processing is efficient, but the electronics are exposed to harsh environmental conditions causing reliability issues
Solution Approach 1:
The sensor system is divided into two separate modules: a sensing element that can withstand harsh environments and a protected electronics module that processes signals in a benign environment. The sensing element includes a resonant circuit with a coil and capacitor that detects changes in resonant frequency, while the electronics module contains the microprocessor and signal processing circuits connected via shielded cable.
Solution Approach 2:
A shielded cable acts as an intermediary transmission medium between the sensing element and the protected electronics module. This cable transmits the resonant frequency signal from the harsh environment to the protected electronics while maintaining signal integrity through shielding, allowing the electronics to remain in a benign environment.
2Measurement precision
If complex electronic circuitry is used to improve measurement accuracy, then measurement precision increases, but device complexity and cost increase
Solution Approach 1:
The sensing element uses a passive resonant circuit consisting of a coil and capacitor that naturally oscillates at a resonant frequency. This self-oscillating circuit eliminates the need for complex active electronic components at the sensing location, reducing circuit complexity while maintaining measurement precision through frequency-based detection.
Solution Approach 2:
The system replaces complex electronic signal processing at the sensing element with a simple resonant frequency measurement. Instead of using complex circuits to detect position changes, the invention uses changes in resonant frequency of the LC circuit, which can be measured accurately with simple frequency counting electronics located in the protected module.
3Volume of moving object
If the sensing element is made compact to reduce size, then device dimensions decrease, but sensitivity and resolution deteriorate
Solution Approach 1:
The invention transitions from amplitude-based or voltage-based sensing to frequency-based sensing. By measuring changes in resonant frequency rather than signal amplitude, the system achieves high sensitivity and resolution independent of the physical size of the sensing element. The frequency measurement provides inherent immunity to signal attenuation and allows compact design without sacrificing precision.
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 accurate and reliable measurements of linear distance, rotary motion, and liquid levels in harsh environments with improved sensitivity and resolution, and allows for simple and reliable redundancy, enabling operation in extreme temperatures, radiation, and vibrations.
Implementation Method 1
a sensing element formed as a section of a coupled slow-wave structure including at least two impedance conductors each curled into a helix or spiral with opposing directions of winding around a dielectric base to form a resonator
Implementation Method 2
create a resonant circuit with the sensing element... This will cause the frequency of the resonant circuit to change proportionally to the movement of the target tube
Implementation Method 3
When an electromagnetic field is excited near a movable object, the parameters of the electromagnetic field, such as resonant frequency, phase, or amplitude, vary with the change of position of the movable object
Data Source
AI summary
A sensing apparatus for use in harsh environments to measure a target characteristic. The apparatus has a sensing element formed as a section of a coupled slow-wave structure including at least two impedance conductors each curled into a helix with opposing directions of winding around a dielectric base to form a resonator. The sensing element provides as an output signal a digital frequency that depends on the value of the measured characteristic. A target tube moves over the sensing element, covering and uncovering portions of the sensing element. An electronics module receives the output signal and displays the measured characteristic. A separate coaxial cable is connected to each impedance conductor on one end and to the electronics module on the other end, with the length of the coaxial cables separating the electronics module from the sensing element by a distance sufficient to avoid exposing the electronics module to the harsh environments.