pH Sensor Safe Harbor Shielding for High Purity Water
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Solution Overview
Problem
High purity water pH measurement systems face accuracy and precision issues due to unstable conductivity caused by the flowing liquid junction between the reference electrode and the solution ground, leading to noisy pH readings.
Innovation Solution
A pH sensor design incorporating a safe harbor to isolate the area between the capillary junction and the solution ground from bulk flow, reducing fluidic currents and stabilizing conductivity, utilizing a laser-drilled capillary with a 1M potassium chloride solution and a stainless steel solution ground electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a flowing liquid junction is used to achieve stable potential at the reference electrode, then the reference electrode potential stability is improved, but the conductivity stability deteriorates due to fluidic currents in high purity water
Solution Approach 1:
The sensor is divided into functionally independent components: the reference electrode assembly with flowing liquid junction, the solution ground electrode, and the measurement electrode. Each component performs its specific function without interfering with others, allowing the reference electrode to maintain stable potential through flowing junction while the solution ground provides stable conductivity reference independent of fluidic currents
Solution Approach 2:
The solution ground electrode acts as an intermediary between the reference electrode and the measurement electrode. It provides a stable electrical reference that is not affected by the fluidic currents in the flowing liquid junction, thereby mediating the connection between the potential-stable reference electrode and the measurement system
2Reliability
If a flowing liquid junction is used to eliminate junction potential, then the reference electrode performance is improved, but measurement precision deteriorates due to noisy pH readings in high purity water
Solution Approach 1:
Different regions of the sensor have optimized local properties: the reference electrode region has a flowing liquid junction for stable potential, while the solution ground electrode region provides a stable conductivity reference. The measurement electrode region is designed to detect pH without being affected by the fluidic currents in the reference electrode region
Solution Approach 2:
The solution ground electrode serves as an intermediary that references the measurement system to a stable electrical potential that is independent of the flowing liquid junction. This intermediary reference allows accurate pH measurement even when fluidic currents are present in the reference electrode compartment
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 safe harbor design significantly reduces noise in pH readings, enhancing precision and accuracy in high purity water pH measurements by maintaining stable conductivity between the capillary junction and the solution ground.
Implementation Method 1
A junction, of some sort, allows electrochemical interaction between a sample solution and the fill solution
Implementation Method 2
a relatively small passageway that is in fluidic communication with both the sample solution and the reference fill solution
Data Source
AI summary
A pH sensor is provided. The pH sensor includes a body, a glass electrode, a reference electrode and a solution ground. The glass electrode is disposed on the body to contact a liquid sample. The reference electrode has a reference fill solution disposed within the body. The solution ground electrode is operably coupled to the body and has a portion of the solution ground electrode that is disposed within a harbor such that a portion of the solution ground electrode is configured to contact the liquid sample. The body has a passageway that extends from the reference fill solution to an aperture proximate the liquid sample.