Wireless SAW Fluid Sensor Eliminates Tank Penetrations
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Solution Overview
Problem
Existing measuring devices for fluid mediums, such as those in fuel tanks for launch vehicles, face challenges in reliably measuring properties like fill level and electrical capacitance while maintaining a tight seal, especially in demanding environments with low temperatures and high mechanical loads, due to the need for multiple coaxial connections that can handle low electrical signals and withstand mechanical stress.
Innovation Solution
A measuring device utilizing surface acoustic wave sensors (SAW) with non-electrically conductive carrier layers and antennas, allowing for wireless interrogation and response signals to measure electrical capacitance between electrodes, reducing the need for multiple connections and enhancing sealing, particularly suitable for cryogenic fluids like liquid hydrogen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple coaxial connections are used to connect electrodes to external measuring amplifiers, then electrical signal transmission is enabled, but the sealing of the environmental envelope deteriorates and device complexity increases
Solution Approach 1:
The patent extracts the electrical connection function from the environmental envelope by using wireless communication. The electrodes are electrically connected to the SAW sensor, which communicates wirelessly with external devices via electromagnetic waves, eliminating the need for coaxial connections through the tank wall and thus preserving the sealing integrity.
Solution Approach 2:
The patent replaces the mechanical coaxial connection system with an electromagnetic field-based wireless communication system. Instead of physically penetrating the environmental envelope with electrical cables, the system uses electromagnetic waves to transmit measurement data, substituting a mechanical-electrical system with an electromagnetic field system.
2Reliability
If multiple coaxial connections with special connectors are used, then low electrical signals can be transmitted, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent extracts the signal transmission function from the physical coaxial cable system and implements it through wireless electromagnetic communication. This eliminates the need for multiple connectors and coaxial connections, significantly reducing device complexity while maintaining signal transmission capability.
Solution Approach 2:
The patent substitutes the complex mechanical connector system with a simplified electromagnetic field-based wireless communication system. The SAW sensor converts electrical signals from the electrodes into acoustic surface waves, which are then converted back to electrical signals and transmitted wirelessly, replacing the cumbersome coaxial connection infrastructure.
3Ease of operation
If feedthrough openings are created for coaxial connections, then electrical access is provided, but the tightness and sealing capability deteriorate
Solution Approach 1:
The patent removes the need for feedthrough openings by implementing wireless communication. The SAW sensor and antenna system enables electrical access functionality without creating any physical penetrations in the environmental envelope, thus maintaining complete sealing integrity.
Solution Approach 2:
The patent replaces the mechanical feedthrough opening system with an electromagnetic field-based wireless communication system. Instead of creating physical openings in the environmental envelope for cable passage, the system uses electromagnetic waves to transmit signals through the envelope wall, eliminating the sealing compromise.
4Reliability
If special connectors suitable for low electrical signals and high mechanical loads are used, then signal transmission reliability is improved, but the manufacturing precision and cost increase
Solution Approach 1:
The patent extracts the signal transmission function from the mechanical connector system and implements it through wireless communication. This eliminates the need for precision-manufactured connectors that must withstand mechanical loads while maintaining sealing, as the wireless system requires no physical connection points.
Solution Approach 2:
The patent substitutes the mechanically robust connector system with an electromagnetic field-based wireless communication system. The SAW sensor and antenna system transmits signals through electromagnetic waves, eliminating the need for precision connectors that must simultaneously handle electrical signals and mechanical stresses.
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 reliable, wireless, and autonomous measurement of fluid properties with improved tank tightness, capable of operating in harsh conditions like low temperatures and high acceleration without the need for local energy sources, and allows for precise determination of fill levels and fluid distribution within the tank.
Implementation Method 1
Surface acoustic wave (SAW) sensors are passive wireless sensors that convert electromagnetic waves of an interrogation signal into acoustic surface waves by an interdigital transducer (IDT) antenna using piezoelectric substrates. These waves are then manipulated by the physical quantity to be measured. The manipulated surface waves are then converted back into an electromagnetic response signal by the IDT and radiated.
Implementation Method 2
The antenna is arranged within the environment and is electrically connected to the interrogator outside the environment by means of an electrical connection through a through-opening through an environmental casing. A wireless query signal from the interrogator is transmitted to the surface acoustic wave sensor via the antenna. The surface acoustic wave sensor can be excited by the query signal, and a wireless response signal can be received via the antenna and transmitted to the interrogator.
Data Source
Figure 1~3
Figure 4~5
AI summary
The invention relates to a measuring device (1) for a fluid medium (2) in an environment (3) comprising at least two electrodes (6) arranged in the environment (3) and spaced apart from each other, which are configured to measure an electrical capacitance in the space between them, characterized in that the measuring device (1) additionally comprises at least one surface acoustic wave (SAW) sensor (7, 11, 13), a non-conductive substrate (15), at least one antenna (16) and at least one interrogator, wherein the electrodes (6) are mounted on the non-conductive substrate (15), and wherein the two electrodes (6) are electrically connected to the surface acoustic wave (SAW) sensor (7, 11, 13).wherein the antenna (16) is arranged within the environment (3) and is electrically connected to the interrogator (19) outside the environment (3) by means of an electrical connection (17) through a through-opening (18) in an environmental envelope (4), wherein a wireless interrogation signal (30) can be transmitted from the interrogator (19) to the surface acoustic wave sensor (7, 11, 13) by means of the antenna (16), wherein the surface acoustic wave sensor (7, 11, 13) can be excited by the interrogation signal (30) and a wireless response signal (38) can be received by means of the antenna (16) and transmitted to the interrogator (19), wherein the response signal (38) can be evaluated by means of the interrogator (19) or a separate evaluation unit in order to measure the electrical capacitance between the electrodes (6) and to determine at least one property of the fluid medium within the environment (3).