Fill-Fluid-Free Capacitive Pressure Sensor
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Solution Overview
Problem
Pressure transmitters filled with dielectric fluid, such as silicone oil, risk contaminating the process fluid if they leak, as existing technologies rely on fill fluids to enhance sensor resolution, leading to potential product contamination and system issues.
Innovation Solution
A pressure transmitter design that eliminates the need for fill fluid by using a capacitive pressure sensor with a pair of process fluid pressure ports and variable capacitors that directly measure differential and line pressures, with deflectable diaphragms and capacitive plates to detect pressure changes without any fill fluid, ensuring the process fluid itself acts on the sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dielectric fill fluid is used in capacitive pressure sensor, then sensor resolution is improved, but risk of fluid leakage and process fluid contamination increases
Solution Approach 1:
The patent removes the dielectric fill fluid from the pressure sensor chamber, eliminating the source of potential contamination. The sensor operates with the process fluid directly acting on the diaphragm without any fill fluid present, thus extracting the harmful element while maintaining sensing capability through alternative capacitive measurement architecture.
Solution Approach 2:
The patent introduces a non-contaminating dielectric barrier layer on the capacitive plates that allows electrical field interaction while preventing direct contact between any residual dielectric material and the process fluid. This intermediary layer enables the sensor to maintain high resolution measurements without the contamination risk associated with traditional fill fluids.
2Measurement precision
If dielectric fill fluid is used to increase capacitance, then sensor resolution is improved, but device complexity and potential leak paths increase
Solution Approach 1:
The patent eliminates the fill fluid chamber and associated sealing structures, simplifying the overall device architecture. By removing the need for fill fluid containment, the sensor design reduces the number of potential leak paths and simplifies the structural complexity while achieving comparable or superior resolution through direct capacitive coupling.
Solution Approach 2:
The patent uses thin dielectric barrier films on the capacitive plates to achieve the necessary electrical isolation and capacitance enhancement without requiring bulky fill fluid reservoirs or complex sealing mechanisms. This thin-film approach reduces device complexity while maintaining the electrical properties needed for high-resolution measurements.
3Quantity of substance
If fill fluid is used in pressure sensor, then capacitance is increased, but reliability decreases due to potential leaks
Solution Approach 1:
The patent removes the fill fluid entirely from the sensing chamber, eliminating the reliability issue associated with potential leaks. The sensor achieves adequate capacitance through direct coupling between the diaphragm and capacitive plates, with or without thin dielectric barrier layers, thereby improving reliability by eliminating the fill fluid containment requirement.
Solution Approach 2:
The patent employs composite structures combining the diaphragm material with integrated capacitive plate assemblies, where the diaphragm itself serves as one element of the capacitive system. This composite approach eliminates the need for separate fill fluid chambers and improves reliability by creating a more integrated, leak-free structure.
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 design prevents fluid contamination by eliminating the risk of fill fluid leaks, maintaining high sensor resolution and accuracy while ensuring the process fluid directly interacts with the pressure sensor, thus avoiding contamination and enhancing operational safety and reliability.
Implementation Method 1
A first variable capacitor is disposed within the pressure sensor and has a capacitance that varies with differential pressure between the process fluid ports
Implementation Method 2
a deflectable diaphragm that deflects in response to pressure applied thereto
Data Source
AI summary
A pressure transmitter is provided. The pressure transmitter includes a pressure sensor including a pair of process fluid pressure ports each having a deflectable diaphragm. A first variable capacitor is disposed within the pressure sensor and has a capacitance that varies with differential pressure between the process fluid ports. A second variable capacitor is disposed within the pressure sensor and has a capacitance that varies with line pressure.