Media Isolated Pressure Sensor Low Aspect Ratio Cavity
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Solution Overview
Problem
Media isolated pressure sensors with high aspect ratios in the pressure transfer fluid cavity exhibit significant temperature-induced offset variation, making them costly and requiring extensive calibration for accurate results.
Innovation Solution
A pressure sensor design featuring a housing with a fluid passageway, a diaphragm, and a carrier forming a transfer fluid cavity with a pressure sensing die, where the aspect ratio of the transfer fluid is minimized to reduce temperature expansion effects, using a pressure transfer fluid like oil or gel within the cavity, and signal conditioning circuitry for output processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pressure transfer fluid cavity with high aspect ratio is used to isolate the pressure sense element from the media, then media isolation and protection are improved, but temperature-induced offset variation increases and calibration cost increases
Solution Approach 1:
The patent changes the aspect ratio parameter of the pressure transfer fluid cavity from high to low. Specifically, the cavity height is reduced to be substantially equal to or less than the cavity width, creating a low aspect ratio geometry that minimizes temperature expansion effects on the pressure transfer fluid while maintaining adequate media isolation functionality.
Solution Approach 2:
The patent uses a pressure transfer fluid (such as oil or gel) as an intermediary substance between the diaphragm and the pressure sense element. This mediator transfers pressure from the media to the sensor while providing media isolation, and the low aspect ratio cavity design minimizes temperature-induced volume changes of this intermediary fluid.
2Reliability
If a pressure transfer fluid cavity with high aspect ratio is used, then media isolation is achieved, but manufacturing cost increases due to calibration requirements
Solution Approach 1:
The patent changes the aspect ratio parameter of the pressure transfer fluid cavity from high to low. Specifically, the cavity height is reduced to be substantially equal to or less than the cavity width, creating a low aspect ratio geometry that minimizes temperature expansion effects on the pressure transfer fluid while maintaining adequate media isolation functionality.
Solution Approach 2:
The patent converts the potential harm of temperature-induced pressure changes in the transfer fluid into a benefit by designing a low aspect ratio cavity. This geometry minimizes the volume of the transfer fluid, thereby reducing temperature expansion effects and eliminating the need for expensive calibration procedures.
3Reliability
If a pressure transfer fluid cavity with high aspect ratio is used, then media isolation is achieved, but device complexity increases
Solution Approach 1:
The patent changes the aspect ratio parameter of the pressure transfer fluid cavity from high to low. Specifically, the cavity height is reduced to be substantially equal to or less than the cavity width, creating a low aspect ratio geometry that minimizes temperature expansion effects on the pressure transfer fluid while maintaining adequate media isolation functionality.
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 reduces temperature-related offset variations and calibration needs, enhancing accuracy and cost-effectiveness by maintaining a low aspect ratio of the pressure transfer fluid, thus improving the sensor's performance and reliability.
Implementation Method 1
Pressure sensors often use a pressure sense element that is configured to detect a pressure of a media to be sensed by converting mechanical stress caused by the incoming pressure of the media into an electrical output signal
Implementation Method 2
pressure from the media is applied to the diaphragm, which is then transferred through the pressure transfer fluid and ultimately to the pressure sense element
Data Source
Figure 1
AI summary
A media isolated pressure sensor is disclosed that helps improve performance and reduce cost. In one illustrative embodiment, a pressure sensor may include a carrier having one or more holes defined therein. The carrier may be coupled to a diaphragm on one side, and a pressure sensing die on the other, with the pressure sensing die in fluid communication with the hole in the carrier. The carrier, diaphragm and pressure sense die may form a transfer fluid cavity, which is filled with a pressure transfer fluid. An input pressure from a media to be sensed may be provided to the diaphragm, which transmits the pressure to the pressure sensing die via the pressure transfer fluid. The pressure sensing die remains isolated from the media to be sensed.