High Temperature Pressure Sensor Assembly
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Solution Overview
Problem
Conventional pressure sensors for turbomachines have limited upper temperature ranges, restricting their ability to provide accurate pressure readings in high-temperature environments.
Innovation Solution
A pressure sensor assembly featuring a MEMS pressure sensing transducer with gold or noble metal electrode pins, a high-temperature plastic inner casing, and a glass-ceramic seal, along with a pressure transmitting fluid, allowing for accurate pressure measurements up to 315°C and beyond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional pressure sensors are used, then the sensor structure is simple and easy to manufacture, but the upper temperature range is limited and accurate readings cannot be obtained above 125°C
Solution Approach 1:
The pressure sensor is divided into multiple functional modules: a pressure sensing transducer (MEMS device) sealed in an inner casing, an outer casing with capsule header, isolator plate, and pressure transmitting fluid system. Each module is designed independently to handle specific requirements, allowing the overall system to achieve high temperature operation while maintaining manufacturability of individual components.
Solution Approach 2:
The sensor employs composite material construction including: (1) inner casing made of high temperature plastic or insulating material, (2) outer casing and capsule header made of high temperature metal, (3) glass-ceramic seal material providing both sealing and electrical insulation, (4) noble metal or gold-plated electrode pins for electrical connectivity, and (5) specialized pressure transmitting fluid with high temperature stability. This multi-material approach enables operation above 299°C while maintaining structural integrity and electrical functionality.
2Measurement precision
If the sensor operates at high temperatures above 299°C, then accurate pressure readings can be obtained, but the pressure transmitting fluid may outgas and cause embolisms in the diaphragm
Solution Approach 1:
The patent selects pressure transmitting fluid based on critical temperature parameters, specifically choosing fluids with maximum operating temperatures above 315°C to prevent outgassing. The fluid is engineered or selected to maintain stable physical and chemical properties throughout the operating temperature range, ensuring reliable pressure transmission without embolism formation in the MEMS diaphragm.
Solution Approach 2:
The pressure transmitting fluid acts as an intermediary medium that isolates the pressure sensing transducer from direct thermal exposure while accurately transmitting pressure information. The fluid's high temperature stability prevents degradation and outgassing, maintaining a reliable interface between the external pressure environment and the sensitive MEMS sensor element.
3Reliability
If gold or noble metal electrode pins are used, then electrical connectivity and high temperature stability are improved, but manufacturing cost increases
Solution Approach 1:
Instead of using noble metals throughout the entire sensor structure, the patent applies gold plating or noble metal electrode pins only at the critical electrical connection points where wire bonding occurs. This localized application provides the necessary electrical stability and solderability at high temperatures while minimizing the amount of expensive material required, thereby reducing overall manufacturing cost.
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 linear signal output and accurate pressure readings at temperatures exceeding 299°C, surpassing the limitations of conventional sensors which fail to operate effectively above 125°C.
Implementation Method 1
a pressure transmitting fluid (e.g. a petroleum oil or other high temperature/low vapor pressure fluid) is disposed in the fluid volume to transmit pressure from the pressure isolator to the pressure sensing transducer
Implementation Method 2
the pressure sensing transducer being connected to the electrode pins via a plurality of wire bonds
Implementation Method 3
the capsule header electrode pin channels including a ceramic seal (e.g. glass-ceramic seal or other high temperature insulating refractory or glassy material) disposed therein such that the capsule header electrode pin channels engage the electrode pins in an insulating sealed relationship
Implementation Method 4
a pressure isolator disposed on the isolator plate and configured to deflect in response to a change in ambient pressure
Data Source
AI summary
A pressure sensor assembly (100) includes a pressure sensor (101) having a pressure sensing transducer connected to a plurality of electrode pins (103) via a plurality of electrode pads (105) disposed on the transducer, an inner casing (107) configured to hold the pressure sensing transducer including a plurality of inner casing electrode pin channels (111) having the electrode pins disposed therein. The pressure sensor further includes an outer casing (115) holding the inner casing therein having a capsule header (117) with a plurality of capsule header electrode pin channels (119) defined therein which can include a ceramic seal (133) disposed therein such that the capsule header electrode pin channels engage the electrode pins in an insulating sealed relationship. The outer casing further includes an isolator plate (127) including an isolator plate fluid port (129) defined therein and a pressure isolator (131) disposed on the isolator plate and configured to deflect in response to a change in ambient pressure. The pressure sensor includes a pressure transmitting fluid disposed in the fluid volume.