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deco comps reading wrong in air rather than
water.
as a twenty year instrument tech i can't see that
with a properly designed unit this should happen. so lets look at the
difference between the two occurances.
force applied to the transducer same in both instances.
force applied to the case same in both instances.
speed at which force was applied. distortion of the
sensing plate unknown. most water test chambers are limited by design to a
certian rate of chnge up and down. unknown design for the air chamber. have seen
this happen with sensing line blow outs. posibility
next thought
desity of the molicule
we know that helium leaks faster than air so lets
assume that air leaks faster than water.
assumption case leak under air condition but
minor
at the cost of deco comps they are not using
absolute transducers they are using guage transducers that use the internal
pressure as a reference for the difference with a corrrection factor for the
compression of the case under pressure. And assume that they have a built auto
calibrate feature for zero drift. if they case pressure exceeds the outside
pressure than the unit goes into recalibrate mode and changes the baseline zero.
thats my idea,
ps shit poor design
rick.
note if you dive with deco comp ensure that the
tranducers are absolute, that means that the reference is absolute vacume. this
is cirtical in high altitude lake diving
rick miller
----- Original Message -----
Sent: Friday, October 28, 2005 5:34
PM
Subject: RE: [PSUBS-MAILIST] Another
nutcase here.
Nobody ever was able
to give a good reason, even a buddy who was on the design team for the one of
the units. This was noted in a number of deco computers?don?t know if it
still occurs.
R/Jay
That's good to know. Do you have
any idea WHY it is inaccurate out of
water?
----- Original Message -----
Sent: Friday,
October 28, 2005 7:46 PM
Subject: RE:
[PSUBS-MAILIST] Another nutcase here.
When I have taken a
dive computer on a chamber run or put it in a pressure pot resulted in
inaccuracies when not submerged in water.
R/Jay
Even when computers
are tested during repairs or calibration they are submerged in water in a
small pressure tank. My old instructor trainer repairs dive equipment and he
said exposure to increased pressure out of water can damage some computers.
Don't know why, pressure is pressure if you ask me. But do you want to risk
it on a $400 dive computer?
-----Original
Message-----
From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org]On Behalf Of Akins
Sent: Friday, October 28, 2005 4:15
PM
To:
personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Another
nutcase here.
That sounds like a good idea
too. But the easiest thing of all would be to use a non water activating
dive computer that would just read
the air pressure as if it was
water pressure.
----- Original Message -----
Sent:
Friday, October 28, 2005 6:00 PM
Subject: RE:
[PSUBS-MAILIST] Another nutcase here.
A little
cleaner setup might be to use an acrylic box that is sealed but vented
to the outside by a couple of tubes. One to bring in the outside water
pressure and one to vent the air out of the box. That way no water is
sloshed aroud in the bucket.
-----Original
Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org]On Behalf Of Akins
Sent: Friday, October 28, 2005
3:08 PM
To:
personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST]
Another nutcase here.
You could put your dive
computers into a small bucket of water inside the dry sub and then the
pressure in the sub
pushing against the water
in the bucket should register the interior pressure and make your dive
computers depth gauge work.
----- Original Message
-----
Sent:
Friday, October 28, 2005 12:41 PM
Subject:
Re: [PSUBS-MAILIST] Another nutcase
here.
So treat
an ambient dry sub like a dive with a big scooter. I haven't
thought much about ambient subs but this has prompted some rules I
might set for myself:
* Be a certified diver. The
education on dive physiology and just general comfort underwater is
crucial.
* Assume you'll be exiting in an emergency.
I'd think entanglement is one of the more likely accidents,
particularly for those of us interested in shipwrecks. :-) In
cold water wear some kind of exposure suit - I can't see myself
wearing my drysuit but at least a thicker wetsuit would help.
Weight belt, mask, survival gear, personal bail out bottle, maybe a
40cf pony? That could be a lot of gear... but still less
than you'd wear on any normal cold water dive. Store an ascent
line/spool in an exterior compartment. Think what you'll do on
the surface, minus your diesel/electric boat. :-(
*
Have partial droppable ballast - as Rick describes. And it
sounds dangerous to have fully droppable ballast.
Right?
* Carry your dive computers and dive a plan.
I've done recreational diving with tables and with just one computer
but would probably spring for a backup computer of a different model
than my primary computer. Yes, in a dry ambient you'd have to
trick them into thinking they were submerged.
It seems
like this being out of the water, even in a small sub may keep you
warmer, and make it easier to manage gear, particularly
breakdowns. You can easily talk to your dive partner because
he's sitting right there behind you. I like it. I have
some of the slowest ears ever for diving and have the hope that
equalizing in air may be easier for me than in water. Also
need to try the ProEar2000 mask or some kind of helmet, which would
be much easier than building a sub to test this idea.
:-)
Great discussions on this list!
Paul
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