It is very common to test multiple DUT's in succession. To reduce the testing time and to improve the stability of the test, two shut-off valves are placed between the setting/measuring equipment and the DUT. Especially for cases with a very small leakage rate, a safe bypass has to be added to the setup in order to fill the DUT quickly. Using such a safe bypass avoids approving a defect product. The solutions to all these ‘catches’ are shown in the flow scheme.
Temperature stabilisation prior to conducting a measurement is essential. For example, due to gas expansion a temperature variation of 2 °C already results in a volume change of 0.7 %. Any leaks smaller that this volume change cannot be measured when the temperature fluctuates.
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