Capacitive Sensor Plates for Downhole Pressure and Temperature Measurement
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Solution Overview
Problem
Downhole pressure and temperature sensors face challenges in harsh environments due to sensitivity to changes in pressure and temperature, requiring technologies that can differentiate between pressure and temperature responses effectively.
Innovation Solution
The development of pressure and temperature sensors using conductor plates with varying coefficients of thermal expansion, where a hermetic seal and adjustable gaps allow for gas retention and venting to isolate responses to pressure and temperature changes, enabling frequency shifts in electromagnetic signals for accurate measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor uses conductor plates with different coefficients of thermal expansion, then temperature response is improved, but pressure sensitivity increases causing cross-contamination
Solution Approach 1:
The sensor structure is segmented into a first conductor plate optimized for temperature response using high CTE material, and a second conductor plate that provides pressure reference. This segmentation ensures that temperature-induced expansions are captured by the first plate while the second plate remains relatively stable, preventing pressure sensitivity from becoming a harmful cross-contamination factor.
Solution Approach 2:
Different regions of the sensor system have different material properties tailored to their specific functions. The first conductor plate uses high CTE material locally where temperature response is needed, while the second conductor plate uses different material properties where pressure stability is required. This local quality differentiation improves temperature response while minimizing unwanted pressure sensitivity.
2Stability of the object's composition
If conductor plates are fixed relative to each other with hermetic seal, then structural stability is improved, but ability to respond to environmental changes deteriorates
Solution Approach 1:
The hermetic seal is designed to be dynamically adaptive rather than rigidly fixed. The seal maintains structural stability while allowing controlled relative movement between the first and second conductor plates in response to temperature and pressure changes. This dynamic design enables the sealed structure to expand, contract, or shift positions without compromising the seal integrity, thus maintaining both structural stability and environmental responsiveness.
3Measurement precision
If gas is retained in adjustable gap between plates, then frequency shift response to pressure is improved, but device complexity increases
Solution Approach 1:
The gas trapped in the adjustable gap between conductor plates serves a dual function: it acts as a spring element providing restoring force and simultaneously serves as the sensing medium that transmits pressure changes to the plates. This self-service approach eliminates the need for additional mechanical springs or complex pressure transmission mechanisms, achieving improved frequency shift response while minimizing device complexity.
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
These sensors effectively isolate pressure and temperature responses, providing accurate and reliable measurements in harsh downhole environments by using the gas retained between plates to adjust frequency based on pressure or temperature changes, reducing cross-sensitivity and enhancing measurement precision.
Implementation Method 1
The first layer has a high coefficient of thermal expansion relative to the first substrate. The second layer has a high coefficient of thermal expansion relative to the second substrate.
Implementation Method 2
A hermetic seal is located at the edges of the first and second conductor plates. The first and second conductor plates are fixed relative to one another, and a gas is retained in an adjustable gap between the first and second conductor plates.
Data Source
AI summary
Methods for making and systems employing pressure and temperature sensors are described. Embodiments include a capacitive element including a first conductor plate and a second conductor plate. Each plate includes a conductor layer formed on a substrate. In a pressure sensor embodiment, seal is positioned at or near the edges of the conductor plates, and a gas retained in a gap defined between the plates. In a temperature sensor embodiment, the gap defined between the plates is in fluid communication with the external environment.