Amperometric Sensor Gel Membrane for Free Chlorine Measurement
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Solution Overview
Problem
Current methods for measuring free chlorine concentration in water distribution networks require frequent maintenance, are costly, and lack efficiency, especially in pressurized conditions, as they often necessitate the use of pH probes or electrolytes that degrade quickly and can lead to water losses.
Innovation Solution
An amperometric sensor with two working electrodes coated with a gel membrane permeable to hypochlorous acid and hypochlorite ions, which establishes a stable diffusion layer, allowing for direct measurement of free chlorine concentration without a pH probe or electrolyte, maintaining functionality for over a year without maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pH probe is used to measure free chlorine concentration, then measurement precision is improved, but device complexity and maintenance frequency increase
Solution Approach 1:
The patent extracts and eliminates the pH probe from the measurement system by using a gel membrane that inherently maintains a stable pH environment. The gel membrane contains a buffer system that automatically regulates pH, removing the need for a separate pH sensing component while preserving measurement accuracy.
Solution Approach 2:
The gel membrane serves multiple functions simultaneously: it acts as a pH stabilizer, a chlorine-permeable barrier, and a protective coating for the electrode. This multi-functionality replaces the need for separate pH probe and membrane components, simplifying the overall device structure.
2Measurement precision
If a pH probe is used to measure free chlorine concentration, then measurement precision is improved, but maintenance frequency increases
Solution Approach 1:
The gel membrane contains an self-regulating buffer system that automatically maintains optimal pH conditions for chlorine measurement without external intervention. The membrane self-adjusts to pH changes in the water sample, eliminating the need for frequent manual calibration and maintenance operations required by external pH probes.
3Ease of operation
If electrolyte is used in the probe cavity, then free chlorine measurement is enabled, but service life decreases due to electrolyte degradation
Solution Approach 1:
The patent replaces the consumable electrolyte with a reusable gel membrane that has a significantly extended service life. The gel membrane's buffer system and permeable structure allow for long-term stable operation without the rapid degradation associated with traditional electrolyte solutions, reducing maintenance frequency and improving reliability.
4Ease of operation
If electrolyte is used in the probe cavity, then free chlorine measurement is enabled, but water losses increase due to bypass circuit requirements
Solution Approach 1:
The patent removes the electrolyte component from the measurement system, eliminating the need for bypass circuits to protect the electrolyte from contamination. The gel membrane's inherent properties allow direct measurement in the main water flow without diverting water through separate measurement paths, thereby preventing water losses.
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 long-term, cost-effective, and compact measurement of free chlorine concentration in water distribution networks, preventing water losses and maintaining accuracy in pressurized conditions, allowing for reliable verification of water quality at the point of distribution.
Implementation Method 1
The membrane is in contact with the working electrodes and comprises a gel capable of letting through hypochlorous acid (HOCl) and hypochlorite ions (OCl−)
Implementation Method 2
The application of a difference in electric potential to the terminals of the reference and working electrodes reduces the hypochlorous acid and produces an electric current which can be measured
Data Source
AI summary
An amperometric sensor circuit for measuring chlorine concentration in water. The circuit includes first and second working electrodes coated with a hydrophilic membrane. A power supply and biasing circuit is configured to deliver a generally constant voltage between the first working electrode and a reference electrode and to generally deliver a constant current between the second working electrode and a counter electrode. A measurement circuit measures the current between the counter electrode and the first working electrode. A processing circuit is provided for determining the chlorine concentration based on the current measured by the measurement circuit.