Liquid Level Sensing System Using Differential Temperature Probes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional liquid level sensing systems for aerospace launch vehicles are fragile and have slow response times, especially under high mechanical shock levels and cryogenic temperatures, which can lead to premature or late engine shutdowns.
Innovation Solution
A liquid level sensing system using two temperature sensing probes spaced apart to provide an output proportional to the time rate of change of the difference between their signals, allowing for rapid detection of liquid level transitions with improved mechanical robustness and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional bare wire sensing elements are used, then the system is simple in structure, but the response time is slow and mechanical durability is poor
Solution Approach 1:
The sensing element is divided into multiple discrete temperature sensing probes spaced apart along the liquid flow direction. Each probe independently measures temperature, and their signals are processed differentially to detect liquid level transitions. This segmentation enables faster response by distributing the sensing function across multiple points rather than relying on a single bare wire element.
Solution Approach 2:
Temperature sensing probes serve as intermediary elements that indirectly detect liquid level through temperature differences caused by liquid contact. The probes convert thermal energy to electrical signals, which are then processed by the differentiating circuit to produce rapid liquid level detection. This intermediary approach allows use of more durable, structured sensing elements while maintaining sensitivity.
2Reliability
If conventional bare wire sensing elements are used, then the system is easy to manufacture, but mechanical durability under high shock levels is poor
Solution Approach 1:
The sensing element is divided into multiple discrete temperature sensing probes spaced apart along the liquid flow direction. Each probe independently measures temperature, and their signals are processed differentially to detect liquid level transitions. This segmentation enables faster response by distributing the sensing function across multiple points rather than relying on a single bare wire element.
Solution Approach 2:
The sensing system employs structured temperature sensing probes with robust construction suitable for cryogenic and high-shock environments. These probes integrate temperature-sensitive elements within durable housings, combining thermal sensitivity with mechanical strength. The composite structure maintains ease of installation while significantly improving resistance to mechanical shock and environmental conditions.
3Use of energy by moving object
If the sensing element has high resistance, then power consumption is reduced, but response time increases
Solution Approach 1:
The system employs a differentiating circuit that processes signals from multiple temperature probes to detect the rate of change of temperature difference. This feedback mechanism amplifies the transient signal during liquid level transitions, enabling rapid detection even with high-resistance probes that consume less power. The differentiating action highlights the dynamic change rather than relying on steady-state signal levels.
Solution Approach 2:
The system uses multiple temperature probes rather than a single element, providing redundant sensing capability. The differential processing of multiple signals enhances the detection of liquid level transitions while allowing each individual probe to operate at lower power levels. The collective action of multiple high-resistance probes maintains sensitivity while reducing overall power consumption compared to a single low-resistance element.
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 achieves faster response times and enhanced mechanical durability, enabling precise fuel level monitoring in aerospace applications, reducing the risk of engine shutdown errors.
Implementation Method 1
a first temperature sensor connected to the housing and configured to output a first signal representing a first temperature measured at the first temperature sensor, a second temperature sensor connected to the housing and configured to output a second signal representing a second temperature measured at the second temperature sensor
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A liquid level sensing system including a housing configured to hold a liquid, a first temperature sensor connected to the housing and configured to output a first signal representing a first temperature measured at the first temperature sensor, a second temperature sensor connected to the housing and configured to output a second signal representing a second temperature measured at the second temperature sensor, and a circuit configured to receive the first and second signals as input and to provide an output signal proportional to the time rate of change of the difference between the first signal and the second signal.