AVS 60th International Symposium and Exhibition
    Vacuum Technology Tuesday Sessions
       Session VT-TuP

Paper VT-TuP1
A Study of Uncertainties at Calibration of Helium Leak Calibrator

Tuesday, October 29, 2013, 6:00 pm, Room Hall B

Session: Vacuum Technology Poster Session and Student-Built Vacuum System Poster Competition
Presenter: Y.W. Lin, National Applied Research Laboratories, Taiwan, Republic of China
Authors: Y.W. Lin, National Applied Research Laboratories, Taiwan, Republic of China
C.P. Lin, National Applied Research Laboratories, Taiwan, Republic of China
C.-N. Hsiao, National Applied Research Laboratories, Taiwan, Republic of China
F.Z. Chen, National Applied Research Laboratories, Taiwan, Republic of China
Correspondent: Click to Email
Helium leak calibrator is used throughout industry for calibration of leak detectors. A calibration system for helium leak calibrator is developed, and the range of calibration is from 10−6 to 10−7 std* cc/s. The origins of the entire system’s uncertainty may be divided into two categories, type A and type B. Type A uncertainty can be determined by making use of a statistical methodology to treat the statistical data of normal distribution and come up with the average standard deviation. The measurement repetitiveness of a set of 35 acquired calibration data was evaluated and reported in the study, and the quantitative value is a measure for the system’s stability. Type B uncertainty includes tracing back the national laboratory (national institute standards and technology, NIST), resolution of Helium leak calibrator, temperature effect, and impurities of working gas. The present estimate of the total uncertainty in the measured leak rate of this artifact at 23℃ at the time of test is 5.2%. This includes a systematic uncertainty of 2.0% in flow meter of the NIST primary Leak standard and 3.2% random errors in the measured leak rate of this artifact. The errors represent three standard deviations. Declared is the relative expanded uncertainty (U) which resulted from the relative standard uncertainty multiplied by the coverage factor k=2. The uncertainty is calculated according to the “Guide to the Expression of Uncertainty in Measurement”. In regular cases it can be assumed that the value of the measure lies with a level of confidence of approximately 95％ within the specified interval. The present research has demonstrated the high stability and great efficacy of the calibration system for helium leak calibrator.