Capacitive Pressure Sensor with Segmented Plates
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Solution Overview
Problem
Capacitive pressure sensors face challenges in harsh environments due to stray capacitance and durability issues, particularly in applications with high temperatures and high pressure ranges, where sensors with many moving parts are prone to breakdowns.
Innovation Solution
A capacitive pressure sensor design featuring a tubular housing with deflatable capacitor plate segments and an anvil within, minimizing stray capacitance and maximizing durability by using a low dielectric insulator and materials tolerant to high temperatures, allowing operation from near freezing to over 500 degrees Fahrenheit and sensing pressures from 0 to 5,000 PSI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitance based pressure sensor is used, then sensitivity to pressure change is improved, but stray capacitance negatively affects performance
Solution Approach 1:
The capacitor plates are segmented into multiple sections (first capacitor plate segment and second capacitor plate segment) positioned on opposite sides of the tubular housing. This segmentation allows the sensor to achieve high sensitivity through multiple capacitive measurements while minimizing stray capacitance effects by distributing the capacitive elements throughout the structure rather than concentrating them in one location.
Solution Approach 2:
The patent transitions from a conventional single-plate capacitor design to a three-dimensional arrangement where capacitor plate segments are positioned on opposite sides of a tubular housing. This dimensional change allows the sensor to utilize the full volume of the housing for capacitive sensing, improving sensitivity while the opposing plate configuration helps cancel out stray capacitance effects.
2Measurement precision
If pressure sensors with many moving parts are used, then sensing capability is improved, but durability deteriorates due to breakdowns
Solution Approach 1:
The patent extracts and eliminates moving parts from the pressure sensor design. The diaphragm is made from a flexible material that deflects in response to pressure changes without requiring mechanical joints, bearings, or other moving components. This extraction of moving parts maintains sensing capability through capacitive detection while dramatically improving durability and reliability.
Solution Approach 2:
The patent replaces traditional mechanical pressure sensing mechanisms with a capacitive sensing system. Instead of using mechanical linkages, gears, or moving components to detect pressure, the system uses changes in capacitance caused by diaphragm deflection. This substitution eliminates mechanical wear and breakdown while maintaining accurate pressure sensing capability.
3Ease of manufacture
If conventional capacitors are used in harsh environments, then cost is reduced, but usability deteriorates due to temperature limitations
Solution Approach 1:
The patent employs composite material construction for the tubular housing and diaphragm assembly. The housing can be made from materials tolerant to high temperatures and harsh environments, while the diaphragm uses flexible materials with appropriate thermal stability. This composite approach enables the sensor to operate in harsh conditions from near freezing to over 500 degrees Fahrenheit while remaining cost-effective.
Solution Approach 2:
The patent changes the operational parameters of the capacitor by using a tubular housing configuration with capacitor plate segments positioned on opposite sides. This geometric parameter change allows the capacitor to withstand high temperatures and harsh environmental conditions that would normally limit conventional capacitor performance, extending usability to extreme temperature ranges.
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 effectively minimizes stray capacitance and enhances durability, enabling accurate pressure sensing across a wide range of temperatures and pressures with minimal moving parts, thus improving the sensor's usability in harsh conditions.
Implementation Method 1
Capacitance of the variable capacitor changes in response to a first change in a size of the first gap and a second change in a size of the second gap
Implementation Method 2
The first capacitor plate segment and the second capacitor plate segment are deflectable in response to the pressure of the fluid
Data Source
AI summary
A pressure sensor for sensing pressure of a fluid includes a tubular housing that has a first capacitor plate segment and a second capacitor plate segment. Each of the first capacitor plate segment and the second capacitor plate segment includes a respective substantially planar inner surface. The pressure sensor also includes an anvil positioned within the tubular housing. The anvil and the tubular housing function as opposite terminals of a variable capacitor. A first capacitor plate side of the anvil and the first capacitor plate segment face each other and have a first gap therebetween. A second capacitor plate side of the anvil and the second capacitor plate segment face each other and have a second gap therebetween. Capacitance of the variable capacitor changes in response to a first change in a size of the first gap and a second change in a size of the second gap.