Liquid Depth Sensing via Bubble Collector and Differential Pressure
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Solution Overview
Problem
Existing liquid depth sensing and identification systems face challenges in detecting small pressure pulse variations due to different types of liquids while measuring the pressure head of liquids in deep containers, as the absolute pressure is high, making it difficult to resolve minute distinctions while providing the necessary range to measure liquid depth from full to empty.
Innovation Solution
The system incorporates a bubble collector and sensors to measure both the overall pressure head and the type/condition of the liquid, using a differential pressure sensor or a mass flow sensor to detect minute variations in pressure or mass flow, allowing for fine resolution of 'bubble signatures' and pressure head measurement, regardless of the liquid depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a purge tube is used to detect liquid depth and type by measuring pressure pulse variations, then liquid identification capability is improved, but measurement precision deteriorates because the pressure variations are extremely small compared to the absolute pressure head
Solution Approach 1:
A bubble collector is introduced as an intermediary component between the purge tube and the pressure sensor. The collector captures bubbles as they emerge from the purge tube, creating a localized region where pressure variations can be measured more effectively. This intermediary structure amplifies the signal by concentrating the bubble flow and pressure variations in a controlled volume, making the minute pressure pulses detectable despite the high absolute pressure head.
Solution Approach 2:
The measurement system is segmented into two distinct measurement functions: (1) measurement of absolute pressure head to determine liquid depth, and (2) measurement of pressure pulse variations to identify liquid type. By separating these measurement functions and using the bubble collector to enhance the pulse signal, the system can accurately measure both the large absolute pressure values and the small variations without interference between the two measurements.
2Adaptability or versatility
If the purge tube extends to the bottom of deep tanks to measure full depth range, then depth measurement range is improved, but pressure head becomes excessively high making bubble signature detection difficult
Solution Approach 1:
The bubble collector serves as a pressure reduction intermediary that allows the purge tube to extend to deep tanks while maintaining detectable bubble signatures. By capturing bubbles in a localized collector volume, the system reduces the effective pressure head that the sensor must measure, enabling accurate bubble signature detection even when the purge tube reaches the bottom of deep containers.
Solution Approach 2:
The system transitions from measuring pressure variations in the vertical depth dimension (which becomes overwhelming in deep tanks) to measuring pressure variations in the localized bubble collection volume. This dimensional shift allows the sensor to focus on the bubble signature characteristics rather than being overwhelmed by the absolute pressure head from deep tank depths.
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 accurate detection of liquid type and condition, along with measuring the liquid depth, by capturing bubbles and measuring the pressure differences within a collector, providing the necessary resolution to distinguish between different liquids even at high pressure heads.
Implementation Method 1
a second or liquid quality or identification pressure sensor being incorporated to detect the minute variations in pressure occurring between the outlet of the purge tube and the pressure within the collector
Implementation Method 2
The system incorporates sensors both for determining the overall pressure head or depth of liquid in a tank, and also for determining the type and/or condition of the liquid at the lower end of the purge tube
Implementation Method 3
As the purge tube emits a stream of gaseous bubbles during operation, the bubbles are captured by the collector as they escape from the end of the purge tube
Data Source
AI summary
The liquid depth sensing and identification system determines both the pressure head or depth, and therefore the quantity, of a liquid in a tank, as well as determining the characteristics of the liquid at the bottom of the probe. Two principles of operation are disclosed herein. The system may use a gas bubble collector about the outlet end of the purge tube, with the difference in height of the collector and purge tube mouths defining the very small difference in pressure head required to resolve the bubble emission characteristics produced in different liquids. Alternatively, the system incorporates a mass flow sensor capable of detecting minute changes in mass flow as bubbles are emitted from the purge tube in order to determine the type and characteristics of the liquid. The system operates using an open loop principle of operation, with no feedback provided to control the purge pump.