| 摘要 |
PURPOSE:To obtain a net gas leakage quantity easily and exactly, by automatically subtracting an ineffective gas leakage quantity from a measured gas leakage quantity, in a leakage detecting device for detecting whether a minute hole exists or not on a vessel wall, and its size, etc. by a gas leakage quantity. CONSTITUTION:For instance, when helium gas is blown from the outside of a vessel whose inside is kept in a vacuum, if a minute hole exists on the vessel wall, helium gas goes into the vessel through its minute hole. A measuring part 1 measures gas passing through the minute hole, namely, quantity of leakage gas. In this measuring part 1, an apparent gas leakage quantity which adds a gas leakage quantity (ineffective gas leakage quantity) existing from before starting a measuring test, in the vessel and the measuring part, to a gas leakage quantity (net gas leakage quantity) passing through the vessel wall as soon as the measuring test is started is measured. Subsequently, the ineffective gas leakage quantity is subtracted from the apparent gas leakage quantity by calculating parts 2, 3, so that the net gas leakage quantity can be obtained automatically. Subsequently, an exhaust characteristic is measured as to the gas leakage quantity, and the leakage quantity in each time is stored as Q=Qt by making the passing time corresponding to a leakage quantity Q. When an apparent gas leakage quantity in case when some measuring test ends is Q' at time t1, an ineffective gas leakage quantity after that time t1 is derived from the relational expression. |
