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Low Frost-Point Humidity Generator

Authors
  • Greenspan, Lewis
Type
Published Article
Journal
Journal of Research of the National Bureau of Standards. Section A, Physics and Chemistry
Publisher
National Institute of Standards and Technology
Publication Date
Jan 01, 1973
Volume
77A
Issue
5
Pages
671–677
Identifiers
DOI: 10.6028/jres.077A.039
PMID: 32189761
PMCID: PMC6728466
Source
PubMed Central
Keywords
License
Unknown

Abstract

A low frost-point humidity generator has been developed at NBS to provide a capability for calibration, testing and research at very low levels of water vapor content in such gases as atmospheric air, carbon dioxide and nitrogen. The generator produces frost points from −30 to −100 °C at ambient pressures from 500 to 200,000 pascals (0.005 to 2 atm.). This is equivalent to mixing ratios of 4 × 10−6 to 51 grams of water vapor per kilogram of dry air and to vapor pressures of 1.4 × 10 −3 to 38 pascals. The generated test gas can be fed to a test chamber with independent temperature control between +25 and −100 °C. The uncertainty of the frost point in the test chamber is estimated not to exceed 0.05 deg C. Intercomparisons with a frost-point hygrometer as well as two gravimetric checks gave results which in all cases agreed to within 0.2 deg C in frost-point temperature.

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