Strain Gage Positioning for Parasitic Force Compensation
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Solution Overview
Problem
Conventional strain gage based pressure sensors are prone to errors in output signals due to parasitic forces such as mounting, thermal-mismatch, and package forces, which can significantly affect the accuracy of fluid pressure measurements.
Innovation Solution
A method for manufacturing pressure sensors involves positioning strain gages on a circular membrane using a mathematical model and finite element algorithms to minimize the impact of parasitic forces by determining optimal positions that reduce the variation between maximum and minimum error signals, thereby enhancing sensitivity to fluid pressure while minimizing sensitivity to parasitic forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gages are positioned on the membrane to improve pressure measurement accuracy, then measurement precision is improved, but sensitivity to parasitic forces increases
Solution Approach 1:
The patent applies asymmetry by positioning strain gages at non-symmetric locations on the membrane. Specifically, the first strain gage is positioned at a first location and the second strain gage at a second location, where these locations are deliberately asymmetric with respect to the membrane center. This asymmetric positioning creates differential strain responses that cancel out parasitic forces while maintaining pressure sensitivity, directly resolving the contradiction between measurement precision and parasitic force sensitivity.
Solution Approach 2:
The patent implements local quality by assigning different positioning criteria to different strain gages based on their specific functional roles. The first strain gage is positioned to optimize for pressure detection, while the second strain gage is positioned to optimize for parasitic force compensation. Each gage's location is independently optimized for its specific purpose, allowing the system to simultaneously achieve high pressure measurement accuracy and low parasitic force sensitivity.
2Power
If strain gages are positioned to maximize output signal, then power is improved, but reliability decreases due to increased susceptibility to parasitic forces
Solution Approach 1:
The patent applies the counterweight principle by positioning the second strain gage specifically to counterbalance the effects of parasitic forces on the first strain gage. The asymmetric positioning creates opposing strain responses that cancel out parasitic force effects while maintaining the overall output signal strength. This allows the sensor to maintain high power output while achieving improved reliability through parasitic force compensation.
3Ease of manufacture
If conventional strain gage positioning is used, then ease of manufacture is maintained, but measurement precision deteriorates due to parasitic force errors
Solution Approach 1:
The patent implements preliminary action by pre-calculating and pre-positioning the strain gages at optimized asymmetric locations before the actual manufacturing process. The positioning method determines optimal locations in advance based on mathematical models, and then these pre-determined positions are used during manufacturing. This approach maintains ease of manufacture by providing clear, predetermined positioning guidelines while achieving superior measurement precision through the optimized asymmetric positioning.
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 approach significantly reduces the influence of parasitic forces on the output signal, leading to improved accuracy and reliability in fluid pressure measurements by optimizing the placement of strain gages on the membrane.
Implementation Method 1
A strain gage based pressure transducer that utilizes an integrated Wheatstone bridge exhibits a high over pressure capability, high output, low offset and linear output
Implementation Method 2
connecting the four strain gages to form a Wheatstone bridge circuit
Data Source
AI summary
A method of manufacturing a pressure sensor is shown, wherein the pressure sensor comprises a port element with a sealing structure and a membrane. Four strain gages will be attached to the membrane. The gages are used in a Wheatstone bridge to sense the fluid pressure. A first finite element action determines a first contour around the membrane central axis with equal compressive strain and a second contour around the membrane central axis with equal tensile strain wherein when fluid pressure is applied to the membrane strain on the first contour is opposite strain on the second contour. A second finite element action determines the four positions of the strain gages on the first and second contour such that the difference between the highest error signal and the lowest error signal at the output of the Wheatstone bridge is minimal under influence of parasitic forces.