Products such as one-way valves are often designed to open at a certain pressure. Production and test engineers need to know at precisely what pressure the valve starts to open (cracking pressure point).Normal burst testers do not detect the pressure change when the valve starts to open because the cracking pressure is so small. Most leak testers cannot determine the cracking pressure because they use merely one pressure sensor upstream from the product being tested. The upstream sensor is constantly supplied with air, so sensing the downstream pressure change is next to impossible.
Uson has published an application note which explains how to effectively and reliably accomplish this difficult test. The application note may be downloaded here.