Pressure difference test

The integral leak test with the pressure difference method is the most accurate test but also some more complicated. The pressure in the test object is compared with the pressure in a standard container which is certainly leak tight. The fine pressure gauge has a pressure range of about 100 mbar full scale, while the total test pressure may be 10 bar.

Both container are filled slowly and simultaneously up to the test pressure. Care has to be taken that the fine leak rate meter is not stressed. After some waiting time for stabilisation of the pressure the pressure difference test can start. So it is possible to have a resolution of the fine pressure gauge of 1 mbar during a total pressure of for example 10 bar. There is also a better chance to overcome the temperature problem. If both containers are similar in dimensions they may change the temperature, if ever, in the same degree and in the same direction.. The leak rate is then calculated in the same manner from volume times pressure difference divided by the measuring time.