Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Calibration of Water Permeation Tubes

Published

Author(s)

Gregory E. Scace, W. Wyatt Miller

Abstract

NIST provides traceability of permeation tube humidity generators to national humidity standards by measuring the water permeation rate of permeation tubes submitted for calibration. Permeation tubes undergoing calibration are installed into a specially built permeation tube humidity generator (PTG). The water vapor concentration of the nitrogen stream produced by the PTG is compared to a similar gas stream produced by the NIST Low Frost-Point Generator, using cavity ringdown spectroscopy (CRDS) as the sensing technique. Comparisons are performed at several points spanning the humidity range produced by the PTG / permeation tube combination. A least-squares fit of the data determines the permeation rate of the tube under test. The expanded relative uncertainty of NIST permeation tube calibrations is 1.8 % with coverage factor k=2, dominated by the Type A uncertainties.
Citation
Special Publication (NIST SP) - 250-82
Report Number
250-82

Keywords

calibrations, permeation tube, trace humidity

Citation

Scace, G. and Miller, W. (2008), Calibration of Water Permeation Tubes, Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD (Accessed April 23, 2024)
Created October 16, 2008