Pressure Sensor Asymmetric Cavity Design for Zero Shift
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Solution Overview
Problem
Existing pressure sensors with multiple diaphragms face challenges in integrating multiple functions while maintaining accuracy, as they cannot employ symmetric structures, leading to difficulties in minimizing zero shift and variations due to temperature and static pressure.
Innovation Solution
A pressure sensor design featuring a planar sensor chip with multiple diaphragms, pressure inlet chambers, and strain gauges, where cavities are strategically placed to adjust stresses and ensure zero output voltage when pressure differences between surfaces are zero, allowing for the integration of multiple functions and suppression of zero shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a pressure sensor includes a plurality of diaphragms to integrate multiple functions, then the functionality of the sensor is improved, but the accuracy of the sensor decreases due to inability to employ symmetric structure
Solution Approach 1:
The patent applies asymmetry principle by intentionally designing asymmetric cavity structures to compensate for the asymmetric arrangement of multiple diaphragms. The cavities are positioned and dimensioned asymmetrically to balance the stress distribution across different diaphragms, thereby minimizing zero shift while maintaining multi-functionality. This resolves the contradiction by transforming the unavoidable asymmetry from a harmful factor into a compensatory mechanism.
Solution Approach 2:
The patent employs parameter changes by adjusting the cavity volumes, positions, and shapes to optimize the stress compensation effect. By varying these geometric parameters, the sensor achieves zero output voltage when pressure difference is zero, even with multiple diaphragms in asymmetric arrangement. This allows maintaining measurement precision while integrating multiple sensing functions.
2Measurement precision
If a symmetric structure is employed to minimize zero shift and variations, then the measurement precision is improved, but the device complexity increases when integrating multiple diaphragms
Solution Approach 1:
The patent uses asymmetry to simplify the overall structure by eliminating the need for complex symmetric arrangements. Instead of creating symmetric multi-diaphragm structures, the patent employs asymmetric cavity designs that achieve the same zero-shift minimization effect with simpler, more flexible structural configurations suitable for integrating multiple functions.
Solution Approach 2:
The cavities act as intermediary elements that mediate between the asymmetric diaphragm arrangement and the required symmetric stress distribution. These cavities serve as stress compensation chambers that balance the mechanical stresses across different diaphragms, enabling precision measurement without requiring complex symmetric structural arrangements.
3Adaptability or versatility
If multiple diaphragms are integrated to detect multiple pressures, then the adaptability of the sensor is improved, but the zero shift and variations due to temperature and static pressure increase
Solution Approach 1:
The patent applies parameter changes by optimizing cavity volumes, positions, and shapes to compensate for temperature and static pressure effects on multiple diaphragms. By adjusting these geometric parameters, the sensor maintains stable zero output across varying environmental conditions while detecting multiple pressure types, thereby improving reliability without sacrificing adaptability.
Solution Approach 2:
The cavities serve as intermediary compensation chambers that isolate and balance the effects of temperature and static pressure on different diaphragms. These intermediaries allow each diaphragm to respond to its specific pressure measurement while the cavity system collectively compensates for environmental variations, maintaining reliability across multiple sensing functions.
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 the simultaneous measurement of differential and absolute pressures with high sensitivity and accuracy, effectively minimizing the impact of temperature and static pressure on output voltage.
Implementation Method 1
a semiconductor piezoresistive pressure sensor in which a piezoresistance is formed in a semiconductor diaphragm that is a pressure sensing portion
Implementation Method 2
an output voltage of a Wheatstone bridge circuit made up of the plurality of strain gauges provided for the diaphragm
Data Source
AI summary
A pressure sensor includes a sensor chip. The sensor chip has two diaphragms, recessed portions that serve as first pressure inlet chambers disposed so as to respectively adjoin top surfaces of the diaphragms, and recessed portions that serve as second pressure inlet chambers disposed so as to respectively adjoin bottom surfaces of the diaphragms. A cavity is provided in the sensor chip such that, when a difference between pressures respectively applied to a top surface and bottom surface of the diaphragm is zero, an output voltage of a Wheatstone bridge circuit made up of strain gauges provided in the diaphragm is zero.