Optical Liquid Level Sensor for Flammable Environments
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Solution Overview
Problem
Conventional liquid level measurement systems, such as those used for fuel level detection in aircraft, face challenges in providing precise and safe measurements in flammable environments, particularly due to the risk of electrical faults and the need for improved sensing methods.
Innovation Solution
A liquid level detection system utilizing a dual thermistor bead point level sensor with optical communication through a fiber optic cable, which isolates the sensor from electrical faults and allows for safe installation in flammable environments by using photonic power and a signal conditioning circuit to generate pulses for determining the liquid level, eliminating the need for electrical conductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional electrical conductors are used to power and signal the level sensor, then the system can operate with conventional electronics, but the system becomes unsafe in flammable environments due to electrical faults and spark risks
Solution Approach 1:
The patent replaces electrical conductors with optical fibers to transmit power and signals to the level sensor. The fiber optic cable transmits modulated light signals that carry both power and data, eliminating electrical conductors entirely. This substitution removes the spark hazard in flammable environments while maintaining system functionality.
Solution Approach 2:
The patent introduces an optical-to-electrical converter as an intermediary device between the optical transmission medium and the level sensor. This converter receives optical signals from the fiber optic cable and converts them to electrical signals for the sensor, enabling electrical isolation while maintaining operational capability.
2Object-affected harmful factors
If electrical conductors are used for power and signaling, then the system structure is simpler, but the system generates harmful electrical faults and sparks in flammable environments
Solution Approach 1:
The patent replaces electrical signal transmission with optical signal transmission through fiber optic cables. The optical interface converts electrical signals to optical signals for transmission through the fiber, and then back to electrical signals at the sensor. This eliminates electrical faults and sparks while introducing optical conversion components.
3Measurement precision
If a single thermistor bead is used for level detection, then the system is simpler, but the system cannot reliably differentiate between cold-dry and hot-wet conditions
Solution Approach 1:
The patent divides the level detection function into two separate thermistor beads instead of using one. Each bead is positioned at different locations or orientations, allowing them to independently sense different conditions. This segmentation enables reliable differentiation between cold-dry, hot-wet, and other conditions through comparative measurement.
Solution Approach 2:
The patent assigns different functional characteristics to different thermistor beads by positioning them in different locations or orientations within the sensor assembly. This allows each bead to sense specific local conditions, enabling the system to differentiate between various thermal and moisture states through their distinct responses.
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 system provides precise liquid level detection with enhanced safety and ease of installation by preventing electrical faults and reducing power consumption, making it suitable for flammable environments and other applications.
Implementation Method 1
A second optoelectronic interface is provided which receives the photonic power and converts it to electrical power. The first optoelectronic interface and second optoelectronic interface are in optical communication through a fiber optic cable.
Implementation Method 2
Heat dissipation of the thermistor bead changes according to the wet/dry state of the bead, which in turn changes its resistance. This is sensed as a voltage change across the thermistor bead.
Implementation Method 3
These are negative temperature coefficient, wire wound resistors that are excited with a steady state current. Heat dissipation of the thermistor bead changes according to the wet/dry state of the bead
Data Source
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Figure 3~4
AI summary
A liquid level detection system (100) comprising a level sensor (102) configured to be at least partially disposed in a liquid storage vessel (104) and exposed to liquid, wherein the level sensor includes a dual thermistor bead sensor, a first optoelectronic interface (106) operatively connected to the dual thermistor bead sensor, wherein the first optoelectronic interface includes a signal conditioning circuit connected to the dual thermistor bead level sensor to provide electrical power to the dual thermistor bead level sensor and to receive voltage readings therefrom and a second optoelectronic interface (108) operatively connected to the first optoelectronic interface (106), and a fiber optic cable (110) optically connecting the first optoelectronic interface (106) to the second optoelectronic interface (108) to provide photonic power to the first optoelectronic interface (106) and to transmit data from the first optoelectronic interface (106) to the second optoelectronic interface (108).