Capacitive Pressure Sensor Thermal Deformation Control
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Solution Overview
Problem
Capacitive pressure sensors face accuracy issues due to thermal deformation causing positional deviations of the electrode face relative to the diaphragm and changes in the gap between them, leading to inaccurate pressure measurements.
Innovation Solution
A capacitive pressure sensor design that includes a pressing mechanism to maintain the insulating positioning member's position parallel to the diaphragm, and a support structure where the electrode member and body have similar thermal deformation volumes to minimize gap changes, ensuring consistent measurement conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the insulating positioning member is pressed in the direction vertical to the diaphragm to keep the gap constant, then the gap between the diaphragm and electrode face remains stable, but the position of the electrode face in the direction parallel to the diaphragm cannot be prevented from deviating due to thermal deformation
Solution Approach 1:
The pressing mechanism is designed to dynamically adjust and maintain the electrode face position in the parallel direction through elastic pressing force, allowing the system to adapt to thermal deformations while keeping the electrode face centered on the diaphragm
Solution Approach 2:
The pressing mechanism changes the pressing force parameter to compensate for thermal expansion differences between the support part and insulating positioning member, maintaining positional accuracy despite temperature variations
2Device complexity
If the support part and insulating positioning member have the same thickness, then the structure is simplified, but thermal deformation causes significant gap deviation due to different thermal expansion coefficients
Solution Approach 1:
The design explicitly accounts for thermal expansion by using materials with different thermal expansion coefficients for the support part and insulating positioning member, and designs their thicknesses to compensate for the resulting differential expansion, maintaining gap stability
Solution Approach 2:
The design uses composite material selection where the support part and insulating positioning member are made of different materials (metal and ceramic/glass respectively) with complementary thermal properties to achieve thermal compensation
3Measurement precision
If the electrode face position deviates from the diaphragm center due to thermal deformation, then the capacitance change detection becomes less accurate, but adding a pressing mechanism increases device complexity
Solution Approach 1:
The pressing mechanism uses the thermal expansion of the support part itself to generate the pressing force on the insulating positioning member, making the system self-regulating without requiring external control mechanisms
Solution Approach 2:
The insulating positioning member acts as an intermediary that translates the thermal expansion of the support part into controlled pressing force on the electrode member, mediating between thermal deformation and positional stability
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 maintains accurate pressure measurements by preventing positional deviations and gap changes due to temperature fluctuations, enhancing measurement accuracy and robustness.
Implementation Method 1
a diaphragm (2) that deforms under pressure
Implementation Method 2
While the support part 11A made of the metal expands with an increase in temperature, the other cylindrical portion of the insulating positioning member 4A made of the glass or ceramic hardly deforms
Implementation Method 3
a capacitive pressure sensor for measuring the pressure of a fluid based on a change in capacitance between a diaphragm that deforms under pressure and an electrode member opposed to the diaphragm
Data Source
Figure 1
Figure 2
Figure 3(a)~3(c)
AI summary
Provided is a capacitive pressure sensor that prevents the position of an electrode face in the direction parallel to a diaphragm from deviating from the position of the diaphragm, and accurately measures pressure. The capacitive pressure sensor includes: the diaphragm that deforms under pressure; an electrode member having the electrode face opposed to the diaphragm with a gap between the diaphragm and the electrode face; a body having one end to which the diaphragm is joined, and accommodating at least a portion of the electrode member; an insulating positioning member that is provided in the body and positions at least the portion of the electrode member in the body; and a pressing mechanism that holds and presses the insulating positioning member or the electrode member in the direction parallel to the diaphragm.