AVS 52nd International Symposium
    Vacuum Technology Tuesday Sessions
       Session VT-TuA

Paper VT-TuA6
Real Time Calibration of Leak Detection Sensitivity

Tuesday, November 1, 2005, 3:40 pm, Room 200

Session: Calibration: Pressure and Flow Metrology
Presenter: X. Chen, Tsinghua University, China
Authors: X. Chen, Tsinghua University, China
T.B. Huang, Tsinghua University, China
L.B. Xiao, Tsinghua University, China
L.Z. Cha, Tsinghua University, China
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The most important characteristic for leak detection is the smallest leak rate that an instrument, method, or system is capable of detecting under specified conditions. It is used to call the smallest detectable leak rate the leak detection sensitivity. One permeation type reference leak with a fixed leak rate is commonly used to calibrate the leak detector and the method has been standardized. It is no doubt that is basic and important to guarantee the instrument in optimized condition. However, the real level of the leak detection sensitivity depends on not only the test instrument, but also the system and methods. The detection limit will be higher or lower if the partial flow pump or accumulation method is used. Sensitivity calibration is necessary to distinguish between leak detector and leak detection. The demand for quantitative leak tests has increased sharply in recent times because the information is more important for the quality control. Real time calibration of the leak detection sensitivity can be achieved by comparing the tested leak rate with a fixed reference leak rate, a series of such reference leak rates or a variable reference leak rate. The last one is optimal for calibration since it provides the reference leak rate in the similar range of the tested leakage rate under the real situation. An adjustable reference leak rate system is put forward with wide dynamic range from 10 @super -7@ to 10 @super -14@Pa.m @super 3@ /s by changing the inlet helium pressure and concentration of a platinum wire-glass reference leak with molecular flow characteristics. The real time calibration for the leak detection has been realized quantitatively not only for the instrument, including the ultra sensitive MSLD system, but also for the methods and system, even for the ultra sensitive leak detection. The detected leak rate under the real situation can be quantitatively calibrated which attracts more and more attention but has not been standardized until now.