Dual NTC Sensor Fill-Level Detection for Lab Cabinets
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Solution Overview
Problem
Existing fill-level measuring devices for laboratory cabinet devices, such as temperature control cabinets, lack reliability and efficiency in detecting the water level in liquid containers used for maintaining humidity, often requiring removal before sterilization and failing to provide precise measurements.
Innovation Solution
A fill-level measuring device utilizing two NTC temperature sensors, where one sensor remains outside the liquid and the other is submerged, with the difference in thermal output and resistance used to detect changes in the liquid level, allowing for continuous monitoring and alerting when the level falls below a threshold, and designed to withstand high temperatures for sterilization without removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single NTC sensor is used for fill-level detection, then the device complexity is reduced, but the measurement precision and reliability deteriorate due to inability to distinguish between temperature changes and fill-level changes
Solution Approach 1:
The single sensing function is segmented into two specialized sensors: a first NTC sensor positioned above the liquid level for reference temperature measurement, and a second NTC sensor positioned at the liquid level for actual fill-level detection. This segmentation allows differentiation between temperature variations and fill-level changes, resolving the measurement precision issue while maintaining manageable device complexity.
Solution Approach 2:
The first NTC sensor acts as an intermediary reference element that provides environmental temperature data independent of liquid contact. By comparing the resistance values of both sensors, the system can distinguish whether resistance changes are due to temperature fluctuations or actual fill-level changes, thereby improving measurement precision without excessive complexity.
2Area of stationary object
If the NTC sensors are positioned close to the liquid container wall for compact design, then the device footprint is reduced, but the measurement precision deteriorates due to thermal interference from the container wall
Solution Approach 1:
The sensor positioning strategy applies local quality by placing the second NTC sensor in direct liquid contact at a specific location away from the container wall, while the first sensor is positioned in the air space above. This localized differentiation ensures that the liquid-contacting sensor measures true liquid temperature and level, while the air-positioned sensor provides reference data, maintaining measurement precision within a compact footprint.
3Productivity
If the fill-level measuring device is designed to withstand sterilization temperatures without removal, then the productivity is improved by eliminating removal/reinstallation steps, but the device complexity increases due to high-temperature material requirements
Solution Approach 1:
The design accepts and adapts to the high-temperature parameter by selecting NTC sensors and container materials rated for sterilization temperatures (typically up to 121°C or 134°C). This parameter change approach allows the device to remain in place during sterilization, improving productivity by eliminating removal/reinstallation operations, while the material selection complexity is managed through standard high-temperature component choices.
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 solution provides a reliable and efficient means to monitor the fill-level of liquid containers within laboratory cabinet devices, ensuring accurate detection and alerting mechanisms without the need for device removal during sterilization, maintaining precise temperature control and humidity levels.
Implementation Method 1
They are supplied with a current, which is as large that self-heating occurs. The current thus initially heats them up and keeps them at an excess temperature above the temperature of their surroundings.
Implementation Method 2
Due to the NTC behavior, according to which the electrical resistance increases with the decreasing temperature—caused by the heat emission to the environment
Implementation Method 3
The first NTC temperature sensor and the second NTC temperature sensor emit a different thermal output to their respective environment if these environments have different thermal conductivities. Since the thermal conductivity of air is much worse than that of a liquid, especially of water, the second NTC temperature sensor emits a higher thermal output than the first NTC temperature sensor.
Data Source
AI summary
The invention relates to a fill-level measuring device for a laboratory cabinet device, for measuring a fill-level in a liquid container in the interior of the laboratory cabinet device, which detects the fill-level by comparing the measurement of two NTC temperature sensors, the first of which is arranged in the air of the interior and the second in the liquid of the liquid container.