Using pressure decay leak detection testing instruments is an industry norm for leak testing parts that have relatively small volumes. The component to be tested is pressurized with air and the pressure transducer in the leak tester measures pressure changes. A drop in pressure indicates a leak in the component.
Most pressure decay panels measure pressure changes in mbar, Pascal, mbar/sec or Pascal/sec. This presents a challenge because leak specifications are usually specified in volumetric units such as cc/sec or cc/min.
In this Application Note, I will provide a solution to easily convert pressure decay readings into volumetric leak rates. I will assume that the total test volume of the part to be tested is known. This is typically available after a test system is designed and built.
It is also necessary to take into consideration the total test volume that includes the test part, the test connection pipe and the internal volume of the test unit.
The relationship between pressure drop, leak rate and volume is derived from the basic gas law and is as follows: -
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