pH Sensor Calibration in Low-Electrolyte Water Using Conductivity Correlation
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Solution Overview
Problem
Existing pH measurement methods in demineralization plants and electrolyte-poor water suffer from long-term drift, leading to inaccurate readings and the inability to achieve high absolute accuracy over extended periods, particularly in applications requiring precise measurement of organic anions and TOC.
Innovation Solution
A software-based recalibration method using a correlation diagram of conductivity and pH values to adjust measurement range limits, compensating for long-term drift by analyzing measurement data points and ignoring outliers, thereby maintaining accurate pH readings over extended periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hardware calibration using buffer solutions is performed frequently, then measurement accuracy is maintained, but system complexity and maintenance requirements increase
Solution Approach 1:
The patent replaces the mechanical/hardware calibration system (buffer solutions, calibration electrodes) with a software-based recalibration method. The software algorithm processes existing measurement data to automatically adjust pH values, eliminating the need for physical calibration materials and procedures while maintaining measurement accuracy.
Solution Approach 2:
The system performs self-calibration by utilizing its own operational data (conductivity and pH measurements taken during normal operation) to recalibrate itself. The method processes measurements from the actual process conditions to determine correction factors, allowing the system to maintain accuracy without external calibration resources.
2Duration of action of stationary object
If KCl replenishment systems are used to extend cell lifespan, then measurement stability is improved, but systematic deviation from true values remains unknown
Solution Approach 1:
The patent implements feedback by continuously monitoring the relationship between conductivity and pH measurements during normal operation. The system uses this feedback data to calculate correction factors that compensate for systematic deviations, allowing the cell to maintain both longevity and accuracy over extended periods.
Solution Approach 2:
The method changes the approach from relying solely on electrolyte replenishment to actively adjusting measurement parameters through software. By calculating correction factors based on the deviation between expected and actual measurement relationships, the system compensates for systematic errors without requiring frequent hardware intervention.
3Measurement precision
If frequent recalibration is performed, then measurement accuracy is maintained, but stable measured values are disrupted
Solution Approach 1:
The system performs preliminary analysis of measurement data during normal operation to determine appropriate correction factors before they are needed. By proactively identifying calibration needs and calculating adjustments in advance, the system can apply corrections without disrupting the stability of ongoing measurements.
Solution Approach 2:
The calibration method is dynamic rather than static, allowing the system to adapt correction factors based on actual operational conditions. The software continuously refines calibration parameters based on real-time data, enabling the system to maintain both accuracy and stability by adjusting to changing process conditions without requiring frequent rigid recalibration events.
Data Source
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AI summary
A method for software calibration of pH measurements in a demineralization plant or electrolyte-depleted water, comprising the steps of: measuring pH values and/or conductivities during the operation of a demineralization plant at at least one measuring point or in electrolyte-depleted water; displaying pairs of conductivity and pH values as points in a correlation diagram with conductivity on the x-axis and pH on the y-axis; identifying an acceptable range of values within the correlation diagram above a theoretical lower pH limit and below a theoretical upper pH limit; using the identified range limits to recalibrate the measurement range limits of the pH measuring devices in the software to compensate for long-term drift of measuring cells used for recording pH and conductivity values.