When we conduct battery changes at Dive Repairs I carry out a pressure test in my purpose built pressure test chamber sourced and imported from Italy.
Unlike other test chambers which have an all round metal construction and a small view port on the top, this test chamber is made from thick plexi glass enabling us to have an all round view of the instrument being tested. It also has plunger system to manoeuvre instruments while pressurised in the chamber.
Dive Repairs Test Chamber
Metal Test Chamber
When testing the seal of a computer, it can be pressurised out of water so if in the event there is a leak in the seal, it will only have air enter the internals of the computer. A max depth of 30m will be set on the computer so when diving to 45m the max depth alarm can be verified. Once the computer has been pressurised (above the water) and left for a period of time, it is then submerged in the water using the plunger. The chamber is then depressurised pretty rapidly with the computer remaining submerged in the water.
Computer is pressurised above the water
The seals are monitored while the chamber is depressurised. If any air had entered the computer when it was initially pressurised (above the water), then as per Boyles Law that air will expand and exit the computer as the pressure in the chamber decreases. This air will be visible because of the chambers all-round clear construction. The plunge system also allows the computer to be rotated enabling all components to be inspected. The computer is dived to the surface following any required safety stops. Rapid ascent alarms are observed to ensure they are working.
This is a safe method of testing the seal of a computer because if there is a break in a seal then it will be identified without allowing any water to enter the internals of the computer. Because the computer does not enter the water until it has been pressurised. Only air can enter the internals of the computer if there is a break in a seal and when the computer is submerged in water, air can only exit from it. If any leaks are visible when depressurising the chamber the computer is immediately raised out of the water while the chamber continues to depressurise.
Computer is submerged in water where any air leaks will be visible. Plunger allows computer to be rotated for an all round view.
If there is a problem seal it can then be fixed as required and pressure tested again. The chamber ensures all pressure tests are correct and the method ensures no computer is ruined in the event it does have a break in a seal. Once the test is complete the no-fly icon is verified.
A pressure test certificate is issued with every pressure test carried out by Dive Repairs.
One way of confirming if your computer has been pressure tested after a battery change is to check it's dive log which should show the dive profile of the pressure test.