boat sju,
You are right, my avatar is a picture of one of our Bergeon dive computer pressure testers. These pressure testers were developed by the Swiss watch industry to test the high-end dive watches (Rolex, Omega, etc) without flooding a $ 10,000 watch due to a defective rear case gasket, a leaky crown or a cracked glass. First, the transparent lucite vessel is filled halfway with water. During Phase 1 of the test, your dive watch (or computer) is hanging in the air (upper half of the vase) while the vessel is pressurized to the desired equivalent depth. In case the watch or computer is not 100% watertight, air at the testing pressure will get into the specimen but not affecting at all the integrity of the parts or the electronics inside. During Phase 2 of the test, the sliding rod where the watch or computer is attached is pushed down to submerge the specimen in water (which is at the same pressure as the air inside it, thus preventing water to get into the unit). During Phase 3 you slowly open the purge valve to depressurize the vessel. Under the hypothesis that the unit is not 100% watertight, you will see air bubbles coming out of the watch or computer. Noticing where the bubbles come from you will learn where the leakage is. You then remove the watch from the pressure tester and correct the leakage. If, on the other hand, the watch or computer was watertight to the test depth, no air would get inside it during Phase 1 and there will be no bubbles coming out during Phase 3. At our shop, we pressure test to 160 feet (50 meters) every computer or dive watch we service. And we have serviced a few thousands of dive computers and dive watches throughout the years without ever flooding a single one.
