Capacitive Pressure Sensor Thermal Expansion Compensation
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Solution Overview
Problem
Conventional capacitive pressure sensors are sensitive to temperature changes, leading to errors in pressure measurements due to thermal expansion and friction between components, which existing solutions attempt to mitigate with multiple electrodes but increase complexity and cost.
Innovation Solution
The design incorporates a single electrode with an electrode extension and an electrically insulative joint, where the geometries and materials of the first body, electrode, and electrode extension are selected to offset thermal expansion, reducing temperature-induced errors and eliminating the need for reference electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive pressure sensors are used, then pressure measurement function is provided, but temperature changes cause thermal expansion and friction leading to measurement errors
Solution Approach 1:
The patent applies thermal expansion principle by designing the electrode extension with specific geometry and material properties that cause it to expand thermally in a controlled manner. This expansion compensates for the thermal expansion of the first body, thereby maintaining a stable gap between the electrode and diaphragm across temperature changes, eliminating temperature-induced measurement errors without requiring reference electrodes
Solution Approach 2:
The patent changes physical parameters including the coefficient of thermal expansion, geometry, and material composition of the electrode extension to achieve thermal compensation. By carefully selecting these parameters, the electrode extension's thermal behavior is tuned to offset the thermal expansion of the first body, maintaining measurement precision across varying temperatures
2Measurement precision
If multiple electrodes including reference electrodes are used to compensate for temperature changes, then temperature error is reduced, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the reference electrode from the sensor structure, replacing it with a single electrode combined with a thermally compensating extension. This simplification achieves temperature compensation through the electrode extension's controlled thermal expansion rather than through differential measurement using multiple electrodes, thereby reducing device complexity while maintaining temperature error compensation
Solution Approach 2:
The electrode extension serves multiple functions: it provides the electrical connection for the electrode and simultaneously acts as a thermal compensation mechanism. By integrating these two functions into a single component with specific geometric and material properties, the patent eliminates the need for separate reference electrodes while maintaining temperature compensation capability
3Measurement precision
If multiple electrodes including reference electrodes are used to compensate for temperature changes, then temperature error is reduced, but manufacturing cost increases
Solution Approach 1:
The patent removes the reference electrode component, reducing the number of parts that need to be manufactured, assembled, and calibrated. This simplification directly reduces manufacturing cost while maintaining temperature compensation through the integrated electrode extension design
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 approach results in pressure sensors with improved thermal performance, reduced complexity, and lower costs, while maintaining reliable and accurate pressure measurements.
Implementation Method 1
the first body, the electrode, and the electrode extension have respective geometries and coefficients of thermal expansion selected such that, in response to changes in temperature, expansion of the electrode and the electrode extension offsets changes in the gap resulting from expansion of the first body
Implementation Method 2
a capacitance between the diaphragm and the electrode
Data Source
AI summary
Disclosed example pressure sensors include: a first body defining a reference pressure cavity; a second body defining a measured pressure cavity and having an inlet configured to receive a fluid; a diaphragm between the reference pressure cavity and the measured pressure cavity; a single electrode comprising a plate portion having a first face facing the diaphragm and separated from the diaphragm by a gap to form a capacitance between the electrode and the diaphragm; an electrode extension fixed to the electrode and extending through an aperture in the first body; an electrically insulative joint disposed between the electrode extension and the first body at least partially within the aperture; and wherein the first body, the electrode, and the electrode extension have respective geometries and coefficients of thermal expansion selected such that, in response to changes in temperature, combined expansion of the electrode and the electrode extension offsets changes in the gap resulting from expansion of the first body.