Semi-permeable Membrane RH Generator for Tap Water Calibration
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Solution Overview
Problem
Existing devices for calibrating relative humidity (RH) sensors require distilled water to create saturated salt solutions, limiting their usability with ordinary tap water.
Innovation Solution
The use of semi-permeable membranes to allow water vapor from tap water to pass through and condense onto a specific salt, creating a known relative humidity environment without the need for distilled water, allowing for calibration of RH sensors with ordinary tap water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If distilled water is used to create saturated salt solutions, then the relative humidity calibration accuracy is ensured, but the ease of operation and accessibility are reduced due to the requirement for specialized water
Solution Approach 1:
A semi-permeable membrane is introduced as an intermediary between the tap water reservoir and the salt solution chamber. The membrane selectively allows water molecules to pass through while blocking impurities, enabling the use of ordinary tap water to create an accurate saturated salt solution without direct contact between the water and salt
Solution Approach 2:
The invention changes the physical state of water from liquid to vapor and back to liquid through phase transitions. Tap water evaporates, the vapor passes through the semi-permeable membrane, and then condenses onto the salt, creating a saturated solution. This phase change process naturally purifies the water while maintaining calibration accuracy
2Ease of operation
If semi-permeable membranes are used to allow water vapor passage, then the ability to use ordinary tap water is enabled, but the device complexity increases due to the additional membrane component
Solution Approach 1:
The semi-permeable membrane performs multiple functions automatically without external intervention: it filters impurities from tap water, selectively transports water vapor molecules, and maintains the separation between the water reservoir and salt solution. The system self-regulates the water transfer process through natural evaporation and condensation cycles
Solution Approach 2:
The semi-permeable membrane utilizes its porous structure to achieve selective permeability. The pores are sized to allow water vapor molecules to pass through while blocking larger impurity molecules, enabling the device to use ordinary tap water while maintaining solution purity through the material's inherent filtering properties
3Quantity of substance
If water vapor is transferred through a semi-permeable membrane, then pure water can be obtained from tap water, but the time required for water transfer increases due to the diffusion process
Solution Approach 1:
The invention utilizes phase transitions (evaporation and condensation) to accelerate the water transfer process. By converting liquid tap water to vapor and then condensing it on the salt side, the system achieves rapid purification and transfer without relying solely on slow diffusion through the membrane, significantly reducing the time required to obtain pure water in the salt solution
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 the calibration of RH sensors using ordinary tap water by generating a pure water vapor environment that equilibrates with the salt, producing a consistent known RH level for sensor accuracy testing.
Implementation Method 1
Vapor from a lower reservoir of ordinary tap water is allowed to pass through a semi-permeable membrane via diffusion due to the gradient pressure difference with the upper chamber
Implementation Method 2
Vapor from a lower reservoir of ordinary tap water is allowed to pass through a semi-permeable membrane via diffusion due to the gradient pressure difference with the upper chamber
Implementation Method 3
The salt then captures the pure water vapor via the vapor pressure differences around the salt and the air and generates an equilibrated air environment around the salt with a known % RH
Data Source
AI summary
Disclosed RH generators include a lower component having a first chamber and an upper component including a second chamber, the upper component being coupled to the lower component to couple the first chamber to the second chamber. The first chamber is configured to contain liquid water and generate 100% RH, while the second chamber is configured to contain salt and generate a second RH less than 100% RH. A first membrane is positioned between the first chamber and the second chamber to allow water vapor to pass between the first and second chambers while blocking liquid water, the salt, and other larger molecules. The upper component is couplable to an RH probe with a second membrane separating the second chamber from the RH probe, which allows water vapor to pass between the second chamber and the RH probe to expose the RH probe to the second RH.