Capacitive Pressure Sensor Radial Slots
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Solution Overview
Problem
Capacitive pressure sensors face challenges in measuring extremely low pressures due to instability in electrode gap spacing and mechanical hysteresis caused by temperature and pressure changes, leading to inaccurate pressure measurements.
Innovation Solution
The introduction of a series of slots in the compliant ring to reduce radial spring constant and enhance radial compliance, allowing for elastic operation against temperature and pressure changes, thereby stabilizing the electrode gap and reducing mechanical strain and shear forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If very narrow gaps are used between the flexible diaphragm and the fixed electrode structure to measure extremely low pressures, then measurement precision is improved, but stability of the sensor output deteriorates due to changes in electrode gap spacing
Solution Approach 1:
The fixed electrode structure is divided into a center electrode and an outer electrode, creating separate measurement paths. The compliant ring is segmented with radial slots that allow independent radial movement of the electrode support, enabling compensation of gap spacing changes while maintaining measurement precision
Solution Approach 2:
The compliant ring's radial spring constant is modified by introducing radial slots, changing its mechanical parameter from rigid to radially compliant. This allows the electrode support to move radially and compensate for gap spacing changes, maintaining sensor output stability while using narrow gaps for precise low pressure measurement
2Stability of the object's composition
If the electrode support is made rigid to maintain electrode gap spacing, then stability is improved, but measurement precision deteriorates due to mechanical hysteresis and shear forces from temperature and pressure changes
Solution Approach 1:
The fixed electrode support is changed from a rigid static structure to a dynamic structure with radial compliance. The radial slots enable the support to move radially in response to temperature and pressure changes, eliminating mechanical hysteresis while maintaining electrode gap spacing stability through elastic deformation
Solution Approach 2:
The rigid electrode support is replaced with a compliant ring structure containing radial slots that act as flexible elements. This thin-walled structure with radial slots provides radial compliance to accommodate thermal and pressure-induced dimensional changes, eliminating shear forces and mechanical hysteresis while maintaining gap spacing stability
3Strength
If clamped joints are used to secure the electrode support to the sensor housing, then structural integrity is improved, but measurement precision deteriorates due to mechanical hysteresis from slip and shear forces
Solution Approach 1:
The clamped joint connection between the electrode support and sensor housing is removed entirely. The radial slots in the compliant ring eliminate the need for rigid clamping, as the slots themselves provide the necessary compliance and positioning without generating mechanical hysteresis or slip
Solution Approach 2:
The rigid clamped joint is replaced with a flexible compliant ring structure containing radial slots. This thin-walled compliant structure maintains structural integrity while eliminating shear forces and mechanical hysteresis associated with clamped joints, as it deforms elastically to accommodate dimensional changes
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 solution improves the precision and stability of pressure measurements by reducing the effects of environmental factors, maintaining calibrated accuracy, and enabling the detection of smaller pressure ranges with reduced electrical noise and temperature coefficients.
Implementation Method 1
The radial slots reduce the radial spring constant of the compliant ring so that the electrode support moves radially to compensate for changes in electrode gap spacing
Data Source
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AI summary
An improved capacitive manometer, the manometer comprises: (a) a diaphragm including a common electrode and (b) an electrode structure including a center electrode and ring electrode, wherein the diaphragm is movable relative to the electrode structure between (i) a zero position when the pressure on each side of the diaphragm is the same and (ii) a maximum differential position when the maximum measurable differential pressure is applied to the diaphragm; and a diaphragm support structure arranged so as to support the diaphragm so that the diaphragm is constrained relative to the electrode structure, and the common electrode is spaced from and axially aligned with the center and ring electrodes relative to an alignment axis of the manometer; and an electrode support structure arranged to support the electrode structure and comprising a compliant ring including at least three flexures integrally formed in the ring and angularly spaced around the alignment axis; wherein the electrode support is clamped in place relative to the diaphragm at the locations of the compliant ring flexures.