Capacitive Pressure Sensor with Triaxial Guard Electrode for High-Temperature Precision
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Solution Overview
Problem
Existing capacitive pressure sensors face challenges in high-temperature applications due to significant temperature variations, which affect material properties and lead to measurement uncertainties, and the integration of temperature sensors is often bulky and prone to parasitic capacitances, degrading measurement precision.
Innovation Solution
A capacitive pressure sensor design that integrates a temperature sensor within the sensor structure, using a triaxial configuration with a guard electrode and dielectric elements, and a triaxial cable structure to minimize parasitic capacitances, allowing for precise temperature measurement close to the membrane and accurate pressure calculation through real-time thermal correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is integrated into the capacitive pressure sensor, then temperature measurement precision is improved, but parasitic capacitance increases and degrades measurement accuracy
Solution Approach 1:
The guard electrode is maintained at the same electric potential as the capacitive electrode through the triaxial cable structure. This equipotential configuration eliminates voltage differences between adjacent conductors, thereby minimizing parasitic capacitance effects while allowing the temperature sensor to be positioned close to the membrane for accurate temperature measurement
2Measurement precision
If the temperature sensor is placed close to the membrane, then temperature measurement accuracy is improved, but mechanical stress on the sensor structure increases
Solution Approach 1:
The temperature sensor is nested within the existing triaxial cable structure, with the sensor positioned close to the membrane but integrated into the protected interior space. This nesting approach allows close proximity for accurate temperature measurement while the surrounding guard electrode and cable structure provide mechanical protection and stress distribution
3Measurement precision
If a triaxial cable structure is used, then parasitic capacitance is reduced, but device complexity increases
Solution Approach 1:
The triaxial cable structure serves multiple functions simultaneously: it provides electrical connections for the capacitive electrode and guard electrode, maintains equipotential conditions to minimize parasitic capacitance, and integrates the temperature sensor within its structure. This multi-functionality reduces the need for separate components and connections, offsetting the initial complexity with consolidated design benefits
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
Enables high-precision pressure measurements in noisy and high-temperature environments with reduced mechanical stress and parasitic capacitance, achieving accuracy below 1% and extending sensor lifespan by minimizing thermal drift and mechanical stresses.
Implementation Method 1
measuring the displacement of a membrane under the effect of a pressure difference by measuring the capacitive coupling between this membrane and an electrode
Implementation Method 2
The membrane, of circular shape, is integral with the walls on its periphery and undergoes a bulging by elastic deformations under the effect of the pressure difference
Implementation Method 3
A thermocouple is added to the sensor to measure the temperature and correct the pressure measurement
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention relates to a capacitive measurement device comprising first measurement means designed to carry out a first measurement and/or detection function in relation to an object placed nearby, said first measurement means comprising: a capacitive electrode (1) and a guard electrode (2), excitation means which maintain the capacitive electrode (1) and the guard electrode (2) at a substantially identical AC electric potential, and first electronic means for measuring the capacitance between the capacitive electrode (1) and the object (20). The invention is characterized in that it further includes second measurement means designed to carry out a second measurement function, said second means being placed substantially in the vicinity of either the capacitive electrode (1) or the guard electrode (2) and maintained by the excitation means at an AC electric potential substantially identical to that of the guard electrode (2). The invention also relates to a method implemented in this device or apparatus.