Acoustic High-Pressure Sensor Using Ultrasonic Fill Liquid
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Solution Overview
Problem
Conventional pressure sensors, such as capacitive and piezoresistive sensors, face challenges in accurately measuring high pressures due to limitations in diaphragm movement, creep, deformation, and sensitivity to chemical attacks, which result in drift and maintenance issues.
Innovation Solution
A pressure sensor design featuring a housing filled with a compressible organic liquid, where the pressure is transmitted to the liquid through an elastically deflectable diaphragm, and the pressure measurement is based on the change in velocity of sound in the liquid, which is measured using ultrasonic transducers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If piezoresistive sensors are used to measure high pressures, then the measurement range can be extended, but zero-point drift occurs due to creep and plastic deformation of materials
Solution Approach 1:
The patent replaces the mechanical piezoresistive measurement system with an acoustic measurement system. Instead of measuring pressure directly through mechanical deformation of piezoresistive elements, the invention uses ultrasonic transducers to measure the velocity of sound in the fill liquid, which changes with pressure. This substitution eliminates the creep and plastic deformation issues inherent in mechanical systems.
Solution Approach 2:
The patent introduces a fill liquid as an intermediary between the pressure to be measured and the measurement system. The pressure is transmitted to the fill liquid, and the velocity of sound in this liquid is measured. This intermediary approach allows indirect measurement that avoids direct mechanical contact and associated deformation problems.
2Stress or pressure
If piezoresistive sensors are used for high pressure measurement, then pressure can be measured, but aging and fatigue phenomena occur in deformable components
Solution Approach 1:
The patent replaces mechanical measurement components that undergo aging and fatigue with acoustic measurement components. The ultrasonic transducers measure pressure-induced changes in sound velocity without experiencing the same mechanical stress cycles, thereby improving reliability and reducing aging effects.
3Stress or pressure
If piezoresistive sensors are used in contact with process media, then pressure can be measured, but chemical attack and corrosion affect sensor durability
Solution Approach 1:
The patent uses a fill liquid as a protective intermediary that isolates the sensitive piezoresistive sensor chip from direct contact with the process medium. The fill liquid transmits pressure while providing chemical protection, preventing corrosion and oxidation of the sensor components.
Solution Approach 2:
The patent replaces direct mechanical contact between the sensor and process medium with an acoustic measurement system through the fill liquid, eliminating the chemical attack pathway while maintaining pressure measurement capability.
4Measurement precision
If capacitive pressure sensors are used, then measurement can be performed, but maximum diaphragm movement limits the maximum pressure measuring range
Solution Approach 1:
The patent replaces the capacitive measurement system that relies on diaphragm movement with an acoustic measurement system. The ultrasonic transducers measure pressure through changes in sound velocity in the fill liquid, which does not require large mechanical displacements and can operate at much higher pressures.
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 solution provides a stable, drift-free, and maintenance-free pressure measurement over a long period, capable of measuring high pressures with high accuracy, and is resistant to chemical attacks and mechanical fatigue.
Implementation Method 1
an elastically deflectable diaphragm (7), which has a rear side (7b) facing the volume (5) filled with the fill liquid and a front side (7a) opposite the rear side (7b), in such a manner that the diaphragm transmits a pressure lying on the front side (7a) of the diaphragm to the fill liquid
Implementation Method 2
a measuring unit (1, 10), which is adapted to ascertaining a variable dependent on velocity of sound in the fill liquid and, based on the measured variable, to determine a pressure measured value representing the pressure lying on the front side (7a) of the elastically deflectable diaphragm
Data Source
AI summary
A pressure sensor for measuring high pressures includes: a housing having a sealed volume filled with a compressible fill liquid, wherein the housing includes an elastically deflectable diaphragm having a rear side facing the filled volume and a front side opposite the rear side such that the diaphragm transmits a pressure applied to the front side of the diaphragm to the fill liquid; and a measuring unit adapted to ascertain a variable dependent on velocity of sound in the fill liquid and, based on the measured variable, to determine a pressure measured value representing the pressure on the front side of the diaphragm, wherein the fill liquid contains an organic compound, which is present in the fill liquid at a volume fraction of greater than 99%.