Density and Viscosity Sensor With Thin Membrane Housing
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Solution Overview
Problem
Existing sensors for measuring fluid density and viscosity are bulky, intrusive, and prone to measurement perturbations due to pressure and temperature effects, limiting their accuracy and usability in small sample chambers or high-pressure, high-temperature environments.
Innovation Solution
A density and viscosity sensor utilizing a resonating element with two distinct resonance modes, coupled to a membrane within a housing of reduced thickness, allowing efficient mechanical vibration transfer and operation at high pressures and temperatures, with a piezoelectric element isolated from the fluid to minimize stress and enhance measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bulky sensor housing with piezoelectric transducer elements is used, then the sensor can perform density and viscosity measurements, but the sensor becomes intrusive and cannot be used in small sample chambers or high-pressure environments
Solution Approach 1:
The patent employs a thin membrane (30-100 micrometers thick) as the housing structure that separates the piezoelectric element from the fluid while maintaining mechanical coupling. This thin-film approach reduces the sensor volume significantly compared to traditional bulky housings, enabling use in small sample chambers and high-pressure environments while preserving measurement capability through the membrane's flexibility and vibration transfer properties
Solution Approach 2:
The patent replaces the traditional mechanical housing structure with a membrane-based system that combines structural support, fluid isolation, and vibration transmission functions. The membrane substitutes for a solid housing, allowing the piezoelectric element to be positioned closer to the fluid interface while maintaining sealing and pressure resistance, thus reducing overall sensor size
2Reliability
If the piezoelectric element is placed inside the sensor housing, then the element can be protected, but the element is exposed to high stress at high pressure and cannot operate accurately
Solution Approach 1:
The membrane serves as an intermediary between the piezoelectric element and the fluid pressure environment. It transmits mechanical vibrations to the piezoelectric element while isolating the element from direct exposure to high fluid pressure and stress, enabling accurate measurements even in high-pressure conditions up to 30 Kpsi
3Device complexity
If the sensor geometry does not allow alignment with fluid flow, then the sensor structure can be simplified, but large measurement perturbations occur at high fluid velocities
Solution Approach 1:
The patent employs a dynamically responsive membrane structure that can adapt to fluid flow conditions. The membrane's flexibility allows it to maintain effective vibration coupling with the piezoelectric element regardless of flow direction or velocity, eliminating the need for complex geometric alignment while ensuring accurate measurements across varying flow conditions
4Measurement precision
If additional temperature and pressure sensors are added for corrections, then measurement accuracy can be improved, but device complexity and cost increase
Solution Approach 1:
The membrane-based piezoelectric sensor system inherently compensates for temperature and pressure effects through its own structural response. The membrane's vibration characteristics automatically reflect the environmental conditions, eliminating the need for separate temperature and pressure sensors. The system self-adapts to environmental variations, maintaining measurement accuracy without additional correction sensors
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 sensor achieves accurate measurements over an extended pressure and temperature range, reducing measurement time and minimizing acoustic wave generation, enabling operation up to 30 Kpsi and 200°C with improved displacement-to-volume ratio and reduced microphonic effects.
Implementation Method 1
The tines are excited to vibrate resonantly and in anti-phase by one or more piezoelectric exciting elements
Implementation Method 2
The resonating element is excited to vibrate resonantly and in anti-phase
Implementation Method 3
The membrane movement generates a large acoustic signal in the fluid
Implementation Method 4
the membrane having a thickness enabling transfer of mechanical vibration between the actuating/detecting element and the resonating element
Data Source
AI summary
A density and viscosity sensor for measuring density and viscosity of a fluid, and method for measuring, are presented herein. The sensor comprises a resonating element, and actuating/detecting element, a connector and a housing. The actuating/detecting element is positioned within a chamber defined by the housing so as to be isolated from the fluid. The resonating element is arranged to be immersed in the fluid, and has a shape defining a first resonance mode and a second resonance mode characterized by different resonance frequencies and different quality factors. The first resonance mode is adapted to move a volume of fluid, and the second resonance mode is adapted to shear a surrounding fluid.