Pressure

[Paul r s]

Whilst driving home this evening I had a thought that I wasn't sure of the answer.
Obviously I'm aware of pressure underwater etc.

but (for example)
(1) if I took my camera housing down to 20m and had an old analog depth gauge inside would the needle move

(2) what about in your drysuit ? Because wouldn't the drysuit surround you in an neutral atmospheric pressure

(3) if neoprene gloves worn under dry gloves (bungee installed to allow air to migrate), as you descend would the neoprene begin to compress

(4) if a 40m rated camera housing was installed with its only gas supply that acted the same way as an adv and opv from a breather. Would it then be able to go much deeper ?

[nickb]

1) No
2) Yes - No, it's ambient
3) Yes
4) Yes - but.....

[Garf]

1) No
2) Yes - No, it's ambient
3) Yes
4) Yes - but.....

lol, good answer.

[dwhitlow]

Agreed with 1-3 but

4) not relavent,.

the depth rating of cameras is the depth at which they will work as specified. this will go deep but buttons might stick.
(my 40m rated camera housing worked flawlessly at 70m)

[Paul r s]

Wouldn't the pressure in the gloves be 1bar, meaning the neoprene gloves wouldn't compress ?

[Barrygoss]

Pressure

Wouldn't the pressure in the gloves be 1bar, meaning the neoprene gloves wouldn't compress ?

Dry gloves, a bag if air round your hands. At ambient pressure
B

[nickb]

I'll expand on the short answers above:

1) Think about Boyle's Law - the volume remains constant (pretty much, it may change minutely), therefore the internal pressure will remain constant. Which is what we desire from a camera housing. A depth gauge measures depth indirectly - what it actual measures is the relative change in pressure. In this case, none - therefore no depth change.

2) When we descend, we need to add gas to our suit in order to maintain the volume of the suit and prevent squeeze, which is uncomfortable and reduces thermal insulation. If you were to ascend from 10m to the surface with the suit valve shut, the volume of gas inside the suit would double. It's the pressure that keeps the gas volume reduced, Boyle's Law again. The pressure inside the suit is the same as the pressure outside the suit, i.e. ambient. Therefore the gauge would show the correct depth.

3) The gloves would compress for the same reason that the depth gauge would register the actual depth, they are responding to the ambient pressure. The gas surrounding them is having the exact same effect as the water would if the dry gloves weren't there.

4) The vulnerability of a camera housing will be in the integrity of the housing body or, more likely, the o-rings and buttons. If the pressure inside can be equalised with the outside water pressure in the same way as the dry suit above, that weakness is eliminated. This is why a CCR can be taken to extreme depths without the hoses collapsing. The problem with operating a camera housing like this would be the camera itself. Clearly, raising the pressure at which the camera is operating will ultimately cause a problem with the camera itself.

[Hot Totty]

Yet again nick beats me to the answer

[dwhitlow]

Yet again nick beats me to the answer

getting slow are we?

[Hot Totty]

getting slow are we?

[dwhitlow]

[Spirit of Guernsey]

I have had my mobile phone inside my drysuit for the last hundred or so dives, doesn't seem to effect it, so safe to assume that a camera would be the same. Unfortunately, they are not too fond of getting wet. If someone was to make a camera housing with an ambient pressure regulator, or even an ambient +0.1bar regulator, it would work without risk of flooding.

[Scuba steve]

Unless you forget to turn on the cylinder ;-)

[Elvis]

Pressure

I thought a number of people have killed phones (especially "glass" fronted smart phones) by leaving them in under suit pockets, etc.?

[Garf]

I thought a number of people have killed phones (especially "glass" fronted smart phones) by leaving them in under suit pockets, etc.?

oh dear, that's unfortunate news, mine comes with on most dives.