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ianmarsh

Member Since 15 Jan 2012
Offline Last Active Sep 18 2014 03:28 PM
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Posts I've Made

In Topic: For Sale: Subal ND3 Housing with GS 180 Viewfinder

06 September 2014 - 02:33 PM

Price drop: $2600 USD

 

ian


In Topic: New Housing "Airlock" Vacuum from Backscatter

17 September 2013 - 09:11 AM

I put a hair across my main o-ring, and pumped down my system to 10" Hg.  It took almost 10 minutes for the vacuum to fall below 5" Hg.  So unless you make sure you pump down your system and check the pressure with the gauge at least 10 minutes later, AND before subsequent dives to make sure nothing got bumped out of place in the camera table, I still see a benefit for the electronic system.

Doug,

 

Good point, indeed.

 

I have the non electronic version... seems like a solid piece of gear. Very reassuring, but:  With that model, a STABLE vacuum reading is critical.

 

If the vacuum is changing, the housing is leaking.

If you start out at -10in/Hg and it "drops" to -5in/Hg the absolute value doesn't matter. It doesn't start to leak when it gets to 0in/Hg.

The ∆ indicates a leak, and if its leaking air, it is leaking water.

 

The point is, with a non monitored system, stability of the initial reading is key. Don't fool yourself into thinking a small change doesn't matter. It does.

 

However, be aware of temperature/pressure fluctuation.

 

ian