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Repeatability and Reproducibility Standard Deviations in the Measurement of Trace Moisture Generated Using Permeation Tubes



Peter H. Huang, Raghu N. Kacker


Permeation-tube moisture generators are commonly used in industry as calibrated sources of water vapor and carrier gas mixtures. This paper describes repeatability and reproducibility uncertainties obtained with these generators in the range 10 nL/L to 100 nL/L. Measurements were performed using three permeation-tube moisture generators of the type used in the semiconductor industry. Four pairs of independent repeat measurements for each nominal level and each generator were made. Two independent methods were used to determine the realized concentration of water vapor. In one method, the calculated value was determined using calibrated permeation rate of permeation-tube and flow rate of dry carrier gas of the permeation-tube generator. This is the industrial method for determining moisture concentration. In the second method, the corresponding measured value was determined using the Low Frost-Point Generator at the National Institute of Standards and Technology (NIST) and a quartz-crystal-micro-balance. The characteristic used to quantify repeatability and reproducibility uncertainties is the calculated value minus the measured value. Repeatability uncertainty ranges from 2 nL/L to 8 nL/L approximately. These uncertainties represent the extent of possible variation in industrial generation of water vapor in carrier gases by permeation-tube moisture generators. The documentary ASTM standard E691-99 was used for statistical analysis.
Journal of Research (NIST JRES) -


humidity standard, interlaboratory evaluations, measurement uncertainty, permeation-tube, repeatability, reproducibility, trace moisture measurement


Huang, P. and Kacker, R. (2003), Repeatability and Reproducibility Standard Deviations in the Measurement of Trace Moisture Generated Using Permeation Tubes, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD (Accessed May 28, 2024)


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Created May 1, 2003, Updated February 17, 2017