Computer Depth Accuracy

[Seaduced]

I have two computers and there is a difference in their depth readings. It appears to be a linear spread (deliberately not using the word error). In other words, the spread at 100' is double the spread at 50'. On the surface, they both read zero. The manufacturer specifications says accuracy is, "+/- 1% of full scale." Full scale is 399'. I'm not sure if they meant they can be off by 4' (okay, 3.99') at any point, but that is the way I read it. So at 100', an 8' spread could be in specs. I would have thought the spec would read, +/- 1% of depth. But, that is not my point.

They are the same make, but different models (probably the same hardware though), the same decompression model and database.

Where I see the greatest affect is the NDL bottom time calculation. I generally never push the NDL, so it isn't a factor in my diving. If I did, I would probably go with the shortest bottom time. Up to the time I got the second computer, I compared mine with my depth gauge and accepted the fact they were close, but never the same.

I was just wondering for those who have multiple computers, how close are the depth readings at depth?

For those with a single computer, have you compared it to your buddy's computer at depth? How close were they?

 

[iztok]

Do you dive fresh or salt water when you notice this?

Reason asking one might be calibrated for salt water only and one can detect fresh water. I have two and they show differently in fresh water while pretty much the same in salt water.

 

[Seaduced]

I have only been in salt water since I got the second computer. The next time I dive fresh water, I will check them.

 

[Scott]

Has this been happening since day one with both or has it been recently that you noticed it hapening? I ask because one of my Sunnto Vyper's started reading shallower than my actual by up to 13' at 100'. I turns out the battery needed replacing even though the boot up said OK.

 

[iztok]

Well what I meant to say is that I only see difference in fresh water and not in salt water. (Since one of my computers detects difference between fresh and salt and other does not (nor it has a setup).

 

[Seaduced]

Well what I meant to say is that I only see difference in fresh water and not in salt water. (Since one of my computers detects difference between fresh and salt and other does not (nor it has a setup).

I don't think either has that feature, but I'll pull out the manual later.

Has this been happening since day one with both or has it been recently that you noticed it hapening? I ask because one of my Sunnto Vyper's started reading shallower than my actual by up to 13' at 100'. I turns out the battery needed replacing even though the boot up said OK.

That's an interesting idea, it could be what's going on. One has a new battery and the other is a year or two old. I've only had the second computer a short time and I replaced the battery when I got it. The difference is still within the specs, though.

 

[TSandM]

I've definitely seen 3' differences among the gauges on a team, but I don't usually dive with two at the same time, so I don't get a chance to compare them over an entire dive. The 3' differences show up on deco, when we want to hang at slightly different places.

 

[Hatul]

I dive with an Oceanic Prodigy and Suunto Vyper and they track remarkable close. Perhaps differ by 1 foot at most.

Can I ask you which models you're referring to? What I would do is compare with a buddy's computer, as one of the two you have may be bad.

Adam

 

[Seaduced]

Can I ask you which models you're referring to? What I would do is compare with a buddy's computer, as one of the two you have may be bad.

Adam

They are Aeris and they are well within the specification for accuracy. At 100' there is a 3' spread. I just wondered if other divers had the same spread or were most computers "dead nuts" on.

Scott said, he was getting a 13' error because his battery was weak, but not enough for a low batt warning. I may have the same issue and plan to change the older battery before the next dive.

 

[Hatul]

They are Aeris and they are well within the specification for accuracy. At 100' there is a 3' spread. I just wondered if other divers had the same spread or were most computers "dead nuts" on.

Scott said, he was getting a 13' error because his battery was weak, but not enough for a low batt warning. I may have the same issue and plan to change the older battery before the next dive.

Aeris is made by Oceanic and they have a reputation for good service. I find it hard to believe that a "weak" battery can cause bad depth readings. After all you can't always dive with a new battery.

I'd check the two computers you have against a third, if one is off call Oceanic and I bet they'll check it out.

Adam