The Determination of the Water Vapor Content in the Pulkovo VKM-100 Multipass Vacuum Cell Using Polymer Sensors of Humidity

TL;DR

This paper evaluates polymer humidity sensors for accurately measuring water vapor in laboratory spectral studies, demonstrating about 5% accuracy within 40-80% relative humidity and discussing ways to improve precision and range.

Contribution

It introduces and validates the use of polymer sensors in a vacuum cell for precise water vapor measurement in spectral research, with detailed laboratory comparison and analysis.

Findings

Sensors achieve ~5% accuracy in 40-80% humidity range.

Laboratory calibration confirms sensor reliability.

Suggestions for improving measurement accuracy and range.

Abstract

In spectral studies of water vapor under laboratory conditions (determination of molecular constants, measurement for spectral transmission functions), the amount of water vapor in the time of the measurements is one of the most essential parameters, which should be determined accurately. We discuss the application for this purpose of polymer sensors of humidity manufactured by Praktik-NC (Moscow) and used in the Pulkovo VKM-100 multipass vacuum cell. These sensors were examined in the laboratory of Lindenberg Meteorological observatory (Germany) by comparison between their readings and those of standard measuring devices for various values of relative humidity, pressure, and temperature. We also carried out measurements of relative humidity in boxes with saline solution, in which the relative humidity that corresponds to a given solution is guaranteed with the accuracy of several tenths of percent. The analysis of the results of the laboratory examination of the sensors and extended sets of measurements made with the Pulkovo cell made it possible to conclude that in measurements in the interval of relative humidity 40-80%, the ~5% accuracy of the measurements for the water vapor content is reached. Further paths are indicated for the increase of the accuracy of measurements and extending the interval of the relative humidity, in which accurate measurements may be carried out.