pressure in milibars and shearwater petrel

[declan long]

So, my sw petrel manual says always surface pressure 1013 milibars, my sw petrel says 1012. why???

declna long

 

[mala]

1013 is a standard for surface pressure.
so if your computer reads 1012 it is about 1mm of water pressure out.

I wouldn't worry about it as surface pressure is rarley at 1013.

 

[teknitroxdiver]

1013 is the pressure on a standard day. It's nearly always either higher or lower as the weather changes.

Sent from my SAMSUNG-SGH-I337 using Tapatalk

 

[declan long]

so why does the manual say it is ALWAYS 1013 and whats the point in this info anyway about pressure in milibars?

 

[Dr. Lecter]

so why does the manual say it is ALWAYS 1013 and whats the point in this info anyway about pressure in milibars?

I'm guessing it's because you obviously didn't read the entire manual and therefore don't understand how the air pressure setting works.

Here's what you're fixated on:

The surface pressure is set when the Petrel is turned on. If the Altitude setting is set to SeaLvl, then surface pressure isalways 1013 millibars

Note that it's only always 1013mB if you've set the Altitude to SeaLvl -- otherwise, it will sense whatever the true atmospheric pressure is when you turn it on, and use/display that as the Surface Pressure.

Which you'd know if you'd read this part of the manual:

The altitude setting when set to ‘Auto’ will compensate for pressurechanges when diving at altitude� If all your diving is at sea level,then setting this to ‘SeaLvl’ will assume that surface pressure isalways 1013 mBar (1 atmosphere)� Further, when diving at altitude, you must turn the computer on
at the surface� If the auto-on safety feature is allowed to turn thecomputer on after a dive has started then the computer assumesthe surface pressure is 1013 mBar� If at altitude this could result inincorrect decompression calculations�

Want to take a guess what happens if you have it set to Auto, last dove it at sea level, then went up to 2000' to go diving and decided to just let the auto-on feature wake the Petrel up as you descended?

If you don't understand why the surface pressure setting is quite important for determining your PO2, you again probably need to look at another computer. The questions you're coming here for are either in the manual and/or a basic understanding of diving physics. Keep this up and you're going to get hurt or dead flying a SW you don't really understand.