Resonant Pressure Sensor Structure to Resist Balloon Effect
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Solution Overview
Problem
Conventional resonant pressure sensors experience a 'balloon effect' at high static pressures, leading to degraded linearity and measurement precision due to peripheral deformation of the diaphragm, making it difficult to achieve high precision measurements under high static pressure conditions.
Innovation Solution
A resonant pressure sensor design featuring a substrate with a cantilever structure and strain-mitigating holes, where the first and second resonators made of semiconductor material with differing impurity concentrations are used to detect static pressure and temperature, respectively, ensuring high linearity and precision across varying static pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional diaphragm structure is used in a resonant pressure sensor, then the sensor can detect pressure changes through resonance frequency shifts, but the peripheral portion deforms under high static pressure causing the balloon effect and degraded linearity
Solution Approach 1:
The substrate is divided into a fixed portion and a separated portion, with the resonator placed only in the separated portion. This segmentation prevents the resonator from experiencing peripheral deformation while maintaining pressure sensing capability through the strain transmitted via the substrate connection.
Solution Approach 2:
The substrate is designed with non-uniform properties: the fixed portion provides structural support and connection to the housing, while the separated portion provides strain transmission to the resonator without experiencing peripheral deformation. This local differentiation resolves the contradiction between structural integrity and measurement linearity.
2Measurement precision
If the resonator is placed on the entire substrate surface, then it can detect strain from pressure changes, but it also experiences peripheral deformation under high static pressure reducing measurement accuracy
Solution Approach 1:
The substrate area is segmented into fixed and separated portions, with the resonator confined to the separated portion. This segmentation isolates the resonator from the balloon effect that occurs in the fixed portion under high static pressure, while maintaining strain detection capability through the connected substrate structure.
Solution Approach 2:
The resonator is extracted from the region susceptible to balloon effect (fixed portion) and placed only in the separated portion. This extraction removes the harmful influence of peripheral deformation on the resonator while preserving the essential strain transmission function through the substrate connection.
3Device complexity
If a single resonator is used for pressure detection, then the structure is simple, but temperature changes also affect resonance frequency making it difficult to distinguish pressure effects from temperature effects
Solution Approach 1:
Two resonators with different pressure sensitivities are combined in the same substrate-separated portion. This merging allows simultaneous detection of pressure and temperature effects, enabling compensation calculations to achieve accurate pressure measurement despite temperature variations.
Solution Approach 2:
The system uses feedback from the second resonator (which has different pressure sensitivity) to compensate for temperature effects on the first resonator. By comparing the resonance frequency shifts of both resonators, the system can distinguish and compensate for temperature-induced frequency changes, maintaining accurate pressure measurement.
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
The design achieves high linearity and excellent measurement precision regardless of the magnitude of static pressure applied, effectively mitigating the balloon effect and enhancing measurement accuracy under high static pressure conditions.
Implementation Method 1
detects a static pressure applied by a pressure-receiving fluid as a change value of a resonance frequency based on a strain arising in the substrate portion
Implementation Method 2
a first resonator that is disposed in the substrate-separated portion and detects as a change value of a resonance frequency based on a strain arising in the substrate portion
Data Source
AI summary
A resonant pressure sensor has high linearity and includes: a housing; and a pressure sensing unit that detects a static pressure based on a change value of a resonance frequency and includes: a housing-fixed portion; a substrate that includes a substrate-fixed portion and a substrate-separated portion; the pressure-receiving fluid that is interposed in a gap between the housing-fixed portion and the substrate and envelops the substrate; and a first resonator that is disposed in the substrate-separated portion and detects the change value of the resonance frequency based on a strain in the substrate caused by the static pressure applied by the pressure-receiving fluid, wherein the first resonator is made of a semiconductor material including an impurity, a concentration of the impurity is 1×1020 (cm−3) or higher, and an atomic radius of the impurity is smaller than an atomic radius of the semiconductor material.