AI air pressure difference.

[Dry_Diver]

Hello,
I have two different AI computers. One of them is an Atmos Elite hoseless. The other is an Atmos AI. I was kinda messing around today with my doubles and came across something that is kinda troubling.

On the left post I had the Ai, on the right I had the Elite. I was getting a pressure difference of about 375 lbs between the two different computers. At first I thought that maybe the isolation manifold was just simply not open to allow the pressure in the two tanks to equalize. Not the case.

I checked the two different computers on one of my wife's tank. I got the same thing. A difference of about 375lbs.

Is this normal that the two different computers would give that big of a difference of a reading? Should I be concerned? Neither my wife or I have ever run out of air. I know that I have had my tanks down to about 300 lbs when I got back on my boat. I know what you are thinking, to low to get back on the boat. Rest at ease. Once the dive was over, I was doing a buoyancy check so I blew the tank down to 400 lbs at 15' no air in the BC or Dry suit (while holding onto the anchor line) to see how my weighting was. Dead calm flat surface.

Anything anyone could chime in on to help out would be great.

Thanks in advance.

 

[scubafanatic]

yeah, a while back I noticed I had one Oceanic Datamax Pro Plus II that was reading approx 250-ish PSI lower than all my other A.I. computers and SPG's. All my other instruments were within 50 - 75 PSI of each other, but this one computer was an outlier.....so I sent it back to Oceanic for a look-see. Oceanic has some sort of standard overhaul which runs a flat $ 160 per computer (at least that's what Scubatoys charged me). I haven't had a chance to hook it up to a tank to see if the PSI 'problem' is resolved though...on the to-do-list. If it were me, 375 PSI 'off' is excessive and I'd definitely have it checked out....those sorts of things really bug me!

 

[fnfalman]

My Sherwood Wisdom 2 is 25-psi lower than my Aeris Elite T3.

 

[Akimbo]

Most electronic pressure transducers specifications I have seen for tank pressure and depth on integrated dive computers are accurate to ¼% full scale. Check the specs on yours and see if they are out of calibration. You may be able to return it to the factory for re-cal for a reasonable fee if they are out of warranty.

 

[vladimir]

Hello,
I have two different AI computers. One of them is an Atmos Elite hoseless. The other is an Atmos AI. I was kinda messing around today with my doubles and came across something that is kinda troubling.

On the left post I had the Ai, on the right I had the Elite. I was getting a pressure difference of about 375 lbs between the two different computers. At first I thought that maybe the isolation manifold was just simply not open to allow the pressure in the two tanks to equalize. Not the case.

I checked the two different computers on one of my wife's tank. I got the same thing. A difference of about 375lbs.

Is this normal that the two different computers would give that big of a difference of a reading? Should I be concerned? Neither my wife or I have ever run out of air. I know that I have had my tanks down to about 300 lbs when I got back on my boat. I know what you are thinking, to low to get back on the boat. Rest at ease. Once the dive was over, I was doing a buoyancy check so I blew the tank down to 400 lbs at 15' no air in the BC or Dry suit (while holding onto the anchor line) to see how my weighting was. Dead calm flat surface.

Anything anyone could chime in on to help out would be great.

Thanks in advance.

We recently had a thread on this. Possibilities you may want to investigate in your owner's manuals are:

a) does either of your computers "normalize" pressure to temperature?

b) is either of them set to keep gas in reserve that is not shown in the pressure reading?

 

[Jax]

Hello,
I have two different AI computers. One of them is an Atmos Elite hoseless. The other is an Atmos AI. I was kinda messing around today with my doubles and came across something that is kinda troubling.

On the left post I had the Ai, on the right I had the Elite. I was getting a pressure difference of about 375 lbs between the two different computers. At first I thought that maybe the isolation manifold was just simply not open to allow the pressure in the two tanks to equalize. Not the case.

I checked the two different computers on one of my wife's tank. I got the same thing. A difference of about 375lbs.

Is this normal that the two different computers would give that big of a difference of a reading? Should I be concerned? Neither my wife or I have ever run out of air. I know that I have had my tanks down to about 300 lbs when I got back on my boat. I know what you are thinking, to low to get back on the boat. Rest at ease. Once the dive was over, I was doing a buoyancy check so I blew the tank down to 400 lbs at 15' no air in the BC or Dry suit (while holding onto the anchor line) to see how my weighting was. Dead calm flat surface.

Anything anyone could chime in on to help out would be great.

Thanks in advance.

Did you swap the transmitters and see if they read the tanks the same, or did the difference swap with the transmitter?

 

[Dry_Diver]

Did you swap the transmitters and see if they read the tanks the same, or did the difference swap with the transmitter?

No, I did not. Only one of the computers is a hoseless

 

[Bob DBF]

First find out which computer is off, put a SPG on and get the tank pressure. Follow Vladimir's advice and if thats a dead end, and it is the wireless try Jax advice with a transmitter from a friend, acquaintance, total stranger, or your local LDS. Then off to the shop with the offending item.

I hope they are not both off by 187#.


Bob
-------------------------------
You only need two tools in life – WD40 and Duct Tape. If it doesn’t move and should, use the WD40. If it shouldn't move and does, use the Duct Tape

 

[Dry_Diver]

Ok, so here is what I did....

I figured that I would start with the obvious first. I changed all three batteries. I changed the batteries in both PC's and the one in the transmitter for the hoseless PC.

After doing this I am still getting a difference but now it is only 125lbs. I think that I can live with that. I compared the reading that I was getting with my friends two and found that all four PC's were with in 150lbs total of each other.

Do you guys think that this is an acceptable difference?

Thanks for all the advice that I have gotten so far. Look forward to hearing your responses.

 

[scubafanatic]

I'm not sure why changing the batteries improved your results....but if it works. 125 PSI 'off' would still annoy me but I suppose it's livable, especially given the amount of extra time and money you'd have to sink into things to perhaps improve the situation, so I'd probably let it go for now and monitor things to see if they remain stable or deteriorate once again.