Liquid Level Meter Using Temperature Difference Feedback
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Solution Overview
Problem
Conventional liquid level detection methods using resistive temperature detectors are prone to erroneous detection due to individual differences in detector characteristics and noise, and require multiple detectors to accurately measure multiple liquid levels, leading to space occupancy and labor-intensive adjustments.
Innovation Solution
A liquid level meter employing a first resistive temperature detector and a temperature measuring body positioned higher than the detector, with a control unit that adjusts current values to maintain a predetermined temperature difference, allowing accurate detection of liquid level changes by analyzing current value changes over time, thereby reducing erroneous detection and detector count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple resistive temperature detectors are used to detect multiple liquid levels, then detection coverage is improved, but device complexity and space occupancy increase
Solution Approach 1:
The detection function is segmented into two distinct components: a temperature measuring body that monitors temperature at a fixed higher position, and a single resistive temperature detector that measures its own temperature at variable liquid levels. This segmentation allows one detector to effectively monitor multiple liquid levels by comparing temperature differences, reducing the need for multiple detectors while maintaining detection accuracy.
Solution Approach 2:
Temperature serves as an intermediary parameter to detect liquid level changes. Instead of directly measuring liquid level with multiple detectors, the system uses temperature difference as a mediator: the temperature measuring body provides reference temperature data, and the resistive temperature detector compares its temperature against this reference to infer liquid level position, thereby reducing detector quantity while preserving detection capability.
2Measurement precision
If resistive temperature detectors are used for liquid level detection, then detection capability is achieved, but erroneous detection occurs due to individual differences in detector characteristics
Solution Approach 1:
The system implements feedback control by continuously monitoring the temperature difference between the resistive temperature detector and the temperature measuring body. When the temperature difference exceeds a predetermined threshold, the control unit adjusts the current supplied to the resistive temperature detector to maintain the temperature difference within the threshold. This feedback mechanism compensates for individual detector variations and noise, significantly improving detection reliability and reducing erroneous detections.
Solution Approach 2:
The system changes the operating parameter (current) of the resistive temperature detector dynamically to maintain a stable temperature difference. By adjusting the current based on the temperature difference feedback, the system compensates for variations in detector characteristics and environmental noise, ensuring reliable detection despite individual detector differences.
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 enables precise liquid level detection independent of detector variations, suppressing errors by setting current limits and improving detection accuracy without the need for multiple detectors, thus optimizing space and production efficiency.
Implementation Method 1
resistive temperature detectors R1 and R2 such as platinum are vertically inserted into a container C
Implementation Method 2
since the heat dissipation constant when the resistive temperature detector is in a liquid phase L is larger than the heat dissipation constant when the resistive temperature detector is in a gas phase G
Implementation Method 3
a temperature measuring body disposed at a position higher than a position of the first resistive temperature detector disposed
Implementation Method 4
when a current value flowing through the first resistive temperature detector has changed by a predetermined constant value or more within a predetermined period of time
Data Source
AI summary
The liquid level meter according to the present invention includes a resistive temperature detector, a temperature measuring body located above it, a temperature detecting unit detecting temperatures of the resistive temperature detector and the temperature measuring body, a current controlling unit determining a current value to be flowed through the resistive temperature detector so that the resistive temperature detector and the temperature measuring body become a predetermined temperature difference, a power supply unit supplying the current of the determined current value to the resistive temperature detector, and a liquid level detecting unit detecting a position of a liquid level. The liquid level detecting unit detects the change in the relative position of the liquid level relative to the resistive temperature detector by determining whether a change width of the current value flowing through the resistive temperature detector during a predetermined period of time is positive or negative, and whether the change width is not less than a predetermined value. As a result, the position of the liquid level can be accurately detected without being affected by the variation in the characteristics of the resistive temperature detector.