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SHAGGY
10-14-2007, 07:41
I am looking at purchasing an air intergrated computer for my son. I am currently using a UWATEC Smart Com and while it is a good computer it has one featrure that I dont care for. It does not give you the actual tank pressure. It figures it as though the outside temp was 68* which usually will read lower than what the actual tank pressure is. Example: My Smart Com will read 2650psi on a tank and when on an analog gauge it will read appx 2900psi. I realize that this gives me a safety margin of appx 250psi but I would prefer a true reading. So I am looking for a good quality air intergrated computer that gives "ACTUAL" real time tank pressure, or do they all figure it like the Smart Com does?

mpd525
10-14-2007, 08:04
i personally like the sherwood wisdom 2, don't own one, but have used on a few times. Simple to read, and control. I never read the manual but figured it all out in just a few minutes. I also think i've read on here before that the oceanic pro plus 2, and the aeris atmos AI, are all basically the same computer but just different housings.

SHAGGY
10-14-2007, 08:07
So,.... Do they give actual tank pressure readings?

Aussie
10-14-2007, 08:09
I like the AI feature of my Suunto Vytec and D9. It gives you accurate readings of cylinder pressure. Well the difference between the two is 1bar. It is spot on with the analogue SPG which I recommend you also get as a backup.
The Suunto's also give a count down in minutes to low cylinder pressure (default is 35bar). This is based on your current air consumption rates. I dont really use this information as you can use your own judgement in working out how much dive time you have left.

Aussie

ScubaToys Larry
10-14-2007, 08:34
I know the Aeris AI (http://scubatoys.com/store/detail.asp?PRODUCT_ID=AtmosAI) / Oceanic Datamax Pro Plus II (http://scubatoys.com/store/detail.asp?PRODUCT_ID=DatamaxPro) / Sherwood Wisdom (http://scubatoys.com/store/detail.asp?PRODUCT_ID=SherwoodWisdom) (Palegic) do give actual tank readings. Switching to one of these over your Uwatec - you will notice a few differences. On the Palegic computers, you can access all the functions without hooking it up to a PC. For example, I know when we carried the Uwatec, I had someone in Cayman that was a bit upset as they had become a DM down there, and had to do a lot of controlled emergency ascents with students, and the ascent rate on the computers is normally a bit slower than what you would do in an emergency, and the alarm would go off... same with the palegics. But instead of pushing a button to turn it off, you had to hook it up to a PC to change it. Same for some other features like switching from metric to imperial, etc.

You will also find a difference in the conservatism levels. The Suunto's, Uwatecs etc are on the very conservative side, while the Palegics are modeled directly from the Padi tables and are more liberal. I personally prefer that, and if I want to be more conservative - I have the ability to tell it to alarm me 5 mintues before I hit deco or 10... etc.

There is also a difference in the display info. The Palegic computers use a display that features a time remaining number in the middle. But that number can be based on 3 different criteria... how much time do you have based on your nitrogen loading, how much time do you have based on your air consumption - and that takes into account the amount of air you want to hit the surface with, your ascent time and safety and deco stops... based on your actual breathing rate translated to Sac time and calculated for actual depth and work load, and it would also take into account your remaining O2 time limit if diving Nitrox and getting close to your oxygen time limits.

It will show you whatever time is your most limiting factor with an icon next to it to indicate which is (a profile icon, a tank icon etc), then if you hit the button, it will scroll to the next... then a few seconds later it reverts back to the most critical time.

This seems to make the display a little less crowded and easier to understand.

So there are some major differences you should be aware of when comparing the different models.

Hope that helps!

SHAGGY
10-14-2007, 08:53
Larry,

Thanks alot for that detailed explination. It really cleared up alot of questions that I had about different features of certain models. I have been looking at the Aeris Atmos AI and the Oceanic DataMax that you guys carry. So basically those two use the same dive formulas (Palegic), and they both show real time tank pressure,.. which are both features that I would like. And it appears that when comparing the price they will both be the same price if you take into account a quick disconnect and compass and download cable. I tried comapring different features on those two models also and they seem somewhat similar. The biggest difference that I could tell is that the display on the Oceanic Datamax is hudge. I think I could read it on the other side of the room, which isnt a bad thing. Is there any other differences that would be worth mentioning, and which one of the two seems to be the most popular.

kyfriedchipper
10-14-2007, 10:27
Thanks for the info Larry - I have been looking into the Oceanic Geo / Atmos AI 2.0 - do these computers function the same way - with the obvious exception of the AI, or are there other differences. Also - would like to get your thoughts / opinions of the value of watch wearability or just to get a huge honkin' computer on my wrist when diving...

ScubaToys Larry
10-14-2007, 10:58
Ok... let me answer the last two posts with one here...

Yes, all the oceanic and aeris computers function the same with the exception of whether they are air integrated. Internally - same stuff... slightly different "foot print" so they look a bit different, and a slightly modified display... nitrogen bars over here instead of over there... etc.

As far as the most popular... We sell more of the Oceanic - but it might be that people who can afford to buy $600 computers have good jobs... folks that have good jobs are older... folks that are older have bad eyes.. folks that have bad eyes like a larger display.

As far as watch... I really prefer a console for me. I don't like things on my wrist... and I have a watch. I don't want to take my watch off to put on a computer, and I don't want to wear my computer as a watch. I'm one of the guys that needs the bigger display - do a datamax is a good choice for me... (Of course.. now I'm going to do the DataMask - but that's a whole different animal... and price tag! But heck... I own a dive shop!)

The new Oceanic Geo (http://scubatoys.com/store/detail.asp?product_id=GEOWristwatch) (or Aeris manta (http://scubatoys.com/store/detail.asp?PRODUCT_ID=AerisMantaDiveComputer) if you want aeris - again - same animal) is actually the first one I've seen that is not too obtrusive in a watch format - and has a pretty good sized display. With my "25% closer and bigger" I can actually see that one pretty good, and it's not too big on my wrist, and I could wear it just as a watch on vacation... So that is a possibility.

Really great questions - but I hate to tell you I'm going to be no help because it really comes down to a personal preference. How's that for a non-answer! :smiley2:

RoadRacer1978
10-14-2007, 11:22
Can't wait to get a computer. Waiting and saving for the one I want. Oceanic VT pro ot VT3 is what I'm looking at right now.

Zenagirl
10-14-2007, 15:15
I dive an Aeris AI and my husband dives the Datamax Pro+2. We've had them for coming onto 4 years and really love them both. I'd recommend the QD for sure, and we both like having the compass on the console as well.

The only downside as far as I"mconcerned is that everything is so right with my Aeris AI and I have no excuse to go hoseless. ;) Though honestly I may not go hoseless since I like the bigger display that consoles offer.

RoadRacer1978
10-14-2007, 15:29
I think I would prefer the hoseless just or convience and I have found I do not like my comass on my console that much. I hate having to pull it around and feels like I have to really strain to keep it in the center of my body with the lubber line straight and everythin level. Never used my compass much until AOW and learned then that the setup I have now is not ideal for me due to the reasons above. A DM I was with had his comp on oe wrist and his compass on the other and I liked that setup. Seemed to work well for him and I think it would work well for me, if not a compass on te wrist then a compass mounted on the BC with a retractor. Those are just my observations from my limited experience.

SHAGGY
10-14-2007, 15:34
Im leaning pretty hard towards the Oceanic DataMax. I'm not that old yet but I sure like those big numbers on it.

Splitlip
10-14-2007, 18:43
I am looking at purchasing an air intergrated computer for my son. I am currently using a UWATEC Smart Com and while it is a good computer it has one featrure that I dont care for. It does not give you the actual tank pressure. It figures it as though the outside temp was 68* which usually will read lower than what the actual tank pressure is. Example: My Smart Com will read 2650psi on a tank and when on an analog gauge it will read appx 2900psi. I realize that this gives me a safety margin of appx 250psi but I would prefer a true reading. So I am looking for a good quality air intergrated computer that gives "ACTUAL" real time tank pressure, or do they all figure it like the Smart Com does?

Ruh-roh. (Astro, not Scubby)

Mental note. If I ever get an AI computer check it against my SPG.

RoadRacer1978
10-14-2007, 18:52
Always a good idea to check it against your SPG. If I ever do end up getting an AI comuter I would much rather it tell me I had less air than I really did as opposed to the other way around. Also another reason to carry an SPG even though you have an AI compter. I think I'd check them against eachother at the beginning of the dive and at least a couple more times throught the dive especially when it was new.

bperrybap
10-15-2007, 04:35
I know this is a bit off topic but it may help
answer some questions people have about why and how the UWATEC
display is different from an SPG and some of
the other AI computers.

There is a LONG explanation below, but the UWATEC doesn't
always show a lower PSI reading than what a SPG would
show. It depends on the temperature.
(Tank volume/size doesn't matter)
Go above 68F and the SmartTec will show a lower pressure than a SPG.
If cooler than 68F the SmartTec will show
a pressure reading that is higher than what a SPG shows.
The closer to to 68F the temperature is, the closer
the SPG and SmartTec pressure readings will be to each other.
At 68F the pressures will match.

Also the lower the pressure the smaller the pressure difference
between a SPG and the SmartTec display will be for any given
temperature. I.e at 3000 PSI the difference will be much
larger than at 500 PSI.

The Palegic computers (Aeris/Oceanic/Sherwood) and most others
I've looked at don't attempt to do this. They just display what
a SPG would display.

--- bill

I believe what the UWATEC guys were trying to do is convert
the tank pressure to a pressure value that represents
how chemists and scientists measure things.
(By trying to factor out external variables like temperature)
Just like a SAC rate is measured by converting things
to a surface pressure, gauge pressures are often converted
to a pressure at a "standard" temperature for comparison
or calculations.
Unfortunately, there isn't 1 single "standard" pressure temperature,
metric and imperial have used different temperatures as
have different standards bodies and government
organizations over the years.

I believe the point of this was to reduce the pressure
swing a diver will see on his gauge (and hence RBT swings)
just due to the air in his tank changing temperatures.
This temperature/pressure calculation would also
help slightly improve the accuracy of a SAC calculation.

There are some draw backs in doing this.

For example, say the temperature of the tank
(air inside it) was 85 degrees, and a normal SPG
reads 3000 PSI. The UWATEC Smart Tec display
(which is compensated to 68F) would read 2906 PSI.
Now if you cooled that tank down to
68F (with no breathing) then the SPG would
now read 2906 PSI and so would the UWATEC.
The UWATEC compensated for a temperature of 68F
so there would be no change in its reading as the
tank and air inside it cooled down to 68F

Now drop that same tank down to 50F and the SPG
will now read 2807 PSI and the UWATEC will still read
2906 PSI!
You can even see this phenomena if you examine the
graph provided in the UWATEC SmartTec manual on
page 42. When the temperature drops below 68F the
SmartTec will show a pressure on the readout
that is higher than what a normal SPG measures.
To see their example follow the 2900 PSI mark on the
left over to the angled dashed line that goes up to around
the 50F mark on the right, then look down where the
2900 PSI line crosses the dashed angled line and you'll
see that the UWATEC display would show 3045 PSI
which is higher than what a SPG would show.

------------------------------------------
One thing to keep in mind is that the pressure delta
due to temperature variation is proportional to the pressure.
In simple terms that means that as the pressure goes
down, the amount a SPG and a SmartTec will differ
goes down.
At 3000 PSI and at 85F the difference is about 100 PSI.
At 500 PSI and the same 85F, the difference is only about 16 PSI.
So all this pressure variation is not something
to stress over at the end of your dive. The reading
on the SmartTec and a SPG will be fairly close regardless
of the temperature. In fact the difference at the end of
the dive due to the temperature compensation is probably
not too much larger than the resolution of the SmartTec
pressure display and definitely less than what you can tell on
an analog SPG.

------------------------------------------

My overall thoughts on temperature compensation are mixed. The
engineer/scientist in me originally thought that adjusting the pressure
for STP (standard temperature) was a really cool thing to do to
increase accuracy; however, in practical usage, and after thinking
about it more, I think it actually creates more confusion and issues
than it really solves.

Even if you like the pressure correction due
to temperature, there is the problem that the computer
really has no way of accurately knowing what the true temperature
of the tank and air inside it is. It has to assume that the
temperature is the same as whatever reading the sensor inside the
computer is taking which is based on the ambient air
or water temperature.

Hook up the SmartTec up to a freshly filled tank that is hot/warm
and the computer will think it is ambient air temperature. As the tank
cools down, if the ambient air temperature remains a constant,
the SmartTec display will show a lower pressure just like a normal SPG.
In this case all the gyrations of the temperature compensation are
not fully compensating for the change in temperature of the tank
because the computer doesn't really know the temperature of the tank
and couldn't tell that the air inside the tank cooled down.

Once in the water, there is also the problem that the temperature
sensor in the computer will detect ambient temperature changes
(water temperature) in a different amount of time than the tank
and air in side the tank will adjust to the water temperature.
The tank and air inside the tank will adjust to water temperature
changes according to its overall mass, which is dependent on the
tank size its material (aluminum/steel), how much air is inside
the tank and how much water movement is flowing over the tank.
Most of these variables the computer does not know.

------------------------------------------

Not temperature compensating has its own set of issues.
Computers like the Palegic computers that provide an Air Time Remaining
that do not temperature compensate have some strange and perhaps
unexpected behaviors as well.
For example, a computer that doesn't compensate for temperature
will "see" the tank pressure droping as the tank cools down
when the tank was initially warmer than the water and assume that
this drop is entirely do to the diver breathing this air. Since
the computer doesn't know that this is going on and assumes the diver
is breathing this air, it will reduce the Air Time Remaining.
As the tank equalizes temperature, the Air Time Remaining will jump
back up a bit as it looks like the diver is now breathing slower since
the pressure is no longer dropping as fast.

The reverse can happen if you are diving somewhere with
a big thermocline that occurs over a small depth change.
As the tank warms up the computer can see the pressure in the tank
rising or dropping much slower and the Air Time Remaining will
temporarily be extended or spike up until the tank equalizes.

The higher the tank pressure in the tank at the time,
the more noticeable these effects will be. At lower pressures,
these effects become too small to be noticed.

These effects are temporary and depending on diving conditions,
tank pressure, and profile may never be seen or encountered.

------------------------------------------


To me, given all the limitations and issues in trying to perform
a temperature compensation on the real-time pressure reading, its value
seems quite limited at best.

------------------------------------------

To me the real value of temperature compensation is in using
it to help increase the accuracy of the SAC calculation
by temperature compensating the air consumption.

In order to temperature compensate the SAC value for the overall dive,
the only pressure values that need to be temperature
compensated are the starting and ending pressures for the dive.
These compensated values could be used to come up with a temperature
compensated total volume of air breathed during the dive.
This removes the affects of the initial pressure drops inside the tank
due to the water temperature being colder than ambient temperature.

But when all this is said and done and compensated for, the maximum
SAC rate error for not accounting for this in tropical
waters will be negligible since air and water temps tend
not to be too far apart. For cold water it will
tend to be less than %5-6.


--- bill

SHAGGY
10-15-2007, 06:04
bperrybap,

That was a very good scientific explination, and I really like my UWATEC except for that one feature, but since my work paid for mine its not such a big deal. Thats why I want a true reading on one that I plan to pay for. I guess a hundred or two psi isnt that much a difference but I just guess I'm a Keep It Simple Stupid kinda guy.

Charlotte Smith
10-15-2007, 07:28
Love my Aeris Epic AI computer and the fact that my buddy and I can monitor each other air from them.....but thats just me....

Scubastud16
10-15-2007, 13:06
Oceanic Pro Plus 2! Man, what a great computer. I have one beef with it, and that is that if your "air" time is less than you "NDC" time, it will only show your "air" time left. If your NDC time is less, then you can switch back and forth, but not the other way around.

bperrybap
10-15-2007, 14:45
bperrybap,

That was a very good scientific explination, and I really like my UWATEC except for that one feature, but since my work paid for mine its not such a big deal. Thats why I want a true reading on one that I plan to pay for. I guess a hundred or two psi isnt that much a difference but I just guess I'm a Keep It Simple Stupid kinda guy.

I agree with you - I like simple. I really like the Palegic AI dive computers.
(I dive the Aeris AI.)
The user interface, display layout, features,
and large thick digits on the display work great for me.

Oceanic/Aeris has been very good about updating
the PC download s/w over the past couple of years.

Something to consider when purchasing another dive
computer is battery replacement. How easy is it,
any special tools needed, and is it something you
want to do yourself?

Another thing to think about is download capabilities.
This is something that is isn't always readily apparent until you
start to actually use it.

My only complaint against my Aeris AI is that
the Palegic computers have much less on board memory
for storing dive log and dive log profile information than
other manufacturers models.

This may or may not be an issue for you depending
if and how you use the download data.

Comparing these similar models
Sherwood Wisdom
Aeris Atmos AI
Oceanic Datamax Pro II
Uwatec Smart Com

Palegic models above do not store air pressure values
during the dive. They only store starting and ending
pressures.
I "think" (not totally sure) but I believe that the Uwatec
models store the air pressure values during each
sample so you can see your air pressure on the graph
of the dive in the PC s/w.

The SmartCom model stores 50 hours of samples at
a 4 second intervals. (Other Uwatec models store 100 hours)
The Palegic models sample rate is programmable
but if you select a 15 second sample rate you get
16 hours of storage. 30 seconds bumps that to 32 hours.
2 seconds reduces it to about 2 hours.

There is also a difference in the total number of dives.
I believe the Uwatec models store up to the last 99 or 100
dives. The Palegic models will only store up to the last 24 dives.

The Palegic models require using the PC s/w to see your
air pressure used for the dive. The Uwatec model
allows you see this on the dive computer in the log book
without the use of the PC s/w.

To me what this all means is that in order to
avoid dive data loss I have to drag along a laptop
on my dive trips because I don't like longer than
15 second sample rates and I easily over run the 16 hour
dive time during a week long trip which reduces my
dive log to 15-16 dives if I didn't download during the tip.

With the additional memory in the Uwatec, the downloading
could be deferred until after the trip.

Even with this limitation, I still prefer the Pelagic
computers for their ease of use and display format
over the other models.

For me things like having a bigger single Dive Time remaining
on the display vs having a separate Air Time remaining
and a NDL time both on the screen
as well as having graphs for ascent rates vs numerical
ascent rates displayed out weigh the reduced
download capabilities.

--- bill

One other thing to note is I believe the Sherwood model
has a history section in its on board logbook
where it tracts the lifetime total number of dives and total
bottom time for the dive computer. The Aeris and Oceanic
models do not do this.

CompuDude
10-15-2007, 14:48
Great explanation, Berry. Just curious, where did your info come from?

Incidentally, with regard to Larry's explanation, he was a little off on one point: Oceanics and Aeries are indeed towards the most liberal of computers, and Suuntos are among the most conservative. Uwatec, however, is not lumped in with the Suuntos, rather, it is considered a middle-of-the-road algorithm, with respect to conservatism.

gtoph
10-15-2007, 18:20
Oceanic Pro Plus 2! Man, what a great computer. I have one beef with it, and that is that if your "air" time is less than you "NDC" time, it will only show your "air" time left. If your NDC time is less, then you can switch back and forth, but not the other way around.


Just a second for the PP2. Works good, with maybe the only [minor] complaint being the attachment of the compass. It's not horrible, but can be kinda difficult to angle the thing downward to have the compass at the right level.... though a slightly longer hose would probably do the trick.

Scubastud16
10-15-2007, 19:03
Sometimes, I wish the hose was a little shorter. I'm somehow manage to get that thing caught on EVERYTHING!

gtoph
10-15-2007, 19:55
Sometimes, I wish the hose was a little shorter. I'm somehow manage to get that thing caught on EVERYTHING!

I just strap it to a retractor on a right shoulder d-ring. No dangly hoses at all ;)

SHAGGY
10-15-2007, 20:01
This thread has really helped clear up quite a few questions that I had about various dive computers. I'm now pretty much leaning towards the Oceanic Data Max unless I hit the Lotto in the meantime and it will then be the Oceanic Data Mask. Even though there are some definate features that I dont really care for about the UWATEC computers,... their new Galileo sol sure looks cool and is loaded with really cool features, but dang that thing sure is $$$$$.

gtoph
10-15-2007, 20:23
This thread has really helped clear up quite a few questions that I had about various dive computers. I'm now pretty much leaning towards the Oceanic Data Max unless I hit the Lotto in the meantime and it will then be the Oceanic Data Mask. Even though there are some definate features that I dont really care for about the UWATEC computers,... their new Galileo sol sure looks cool and is loaded with really cool features, but dang that thing sure is $$$$$.


Haven't actually used the data mask, but Oceanic had it out at our LDS's big sale event back in the spring. Personally, I think the concept is kinda cool, but I'm not sold on it yet. First, it's too darn expensive. Yes, I know, it's a mask and a computer, but still. And not that I've lost or destroyed a regular mask yet, but that would be a much more expensive mistake. To bad you couldn't detach the computer part somehow. Anywho, I'll give it a year or so for them to make refining changes and lower the price before I would seriously consider it.

Bigg_Budd
10-15-2007, 20:38
Oceanic makes great AI computers. I'm giving my VT Pro to the wife and opting for the VT3. I like being able to read her tank pressure from my computer.

SHAGGY
10-15-2007, 21:43
Oceanic makes great AI computers. I'm giving my VT Pro to the wife and opting for the VT3. I like being able to read her tank pressure from my computer.


I had heard rumors that you have to be extremely close to read your buddy's info with those wireless units, but I have never used one. I'm curious of what the actual "signal" distance is.

gtoph
10-15-2007, 22:32
Oceanic makes great AI computers. I'm giving my VT Pro to the wife and opting for the VT3. I like being able to read her tank pressure from my computer.


I had heard rumors that you have to be extremely close to read your buddy's info with those wireless units, but I have never used one. I'm curious of what the actual "signal" distance is.


I've heard/read similar things. I know they are much improved since the first models, but from what I've read you still have to be relatively close for the signals to be picked up.

Bigg_Budd
10-16-2007, 07:27
Oceanic makes great AI computers. I'm giving my VT Pro to the wife and opting for the VT3. I like being able to read her tank pressure from my computer.

The range isn't bad, between 3-5 feet, but not great for SOBs (same ocean buddies). It's not really meant to monitor their pressure through the dive, just so you can "check in" during the dive. However, seeing as she IS my wife (and she's recently OW certified), I'm never far from her underwater. :)

charlesml3
10-16-2007, 09:15
I was thinking that they designed that computer so you could monitor your primary tank and your pony from one console. Were they really after the ability to check your buddie's pressure?

-Charles

CompuDude
10-16-2007, 11:01
I was thinking that they designed that computer so you could monitor your primary tank and your pony from one console. Were they really after the ability to check your buddie's pressure?

-Charles

Multi-tank setups are an option with these computers, but there is a specific "buddy check" feature that is also built in.