Coulometric trace humidity measurement in technical gases

Area of Science:

• Analytical Chemistry
• Sensor Technology
• Gas Analysis

Background:

• Accurate trace humidity measurement is crucial in various industrial technical gases.
• Miniaturized planar coulometric sensors offer potential for precise humidity detection.
• Understanding sensor performance across different gas matrices is essential for reliable application.

Purpose of the Study:

• To evaluate the performance of miniaturized planar coulometric sensors for trace humidity measurement.
• To develop and validate calibration functions for sensors in technical gases.
• To assess sensor reliability and identify potential interferences in different gas environments.

Main Methods:

• Trace humidity measurement using miniaturized planar coulometric sensors in hydrogen, nitrogen, helium, nitrous oxide, and synthetic air.
• Generated humidity determined using a precision dew point hygrometer as a reference.
• Nonlinear calibration functions developed correlating sensor signal (electric current) and reference humidity.
• One-way analysis of variance (ANOVA) used to test calibration function parameters.

Main Results:

• Coulometric sensors achieved trace humidity measurement with expanded uncertainty below 2 K (k=2) in all tested gases.
• Averaged calibration functions were applicable for nitrogen, helium, nitrous oxide, and synthetic air.
• Hydrogen exhibited significantly higher sensor signals due to a recombination effect, requiring individual sensor calibration.

Conclusions:

• Miniaturized coulometric sensors are effective for continuous trace humidity monitoring in diverse technical gases.
• Gas-specific calibration strategies are necessary, particularly for hydrogen, due to recombination effects.
• The developed methodology ensures reliable and precise humidity measurements in demanding industrial applications.