Dive Computer No Deco Computations Question

[butterwm]

While we are not new to diving we are new to the dive computer world. We started out with basic Suunto Vypers for the first couple years. We just upgraded to Apple Watch Ultra 2/Ocenaic+ this year. We are running both computers together on our dives. We are noticing that the No Deco times are considerably different between the two computers (30+ minute split). While I am not an expert at settings on either device we went in and look at the conservatism/gradient settings on both devices. They are both set at 0 which is the most conservative mode. Any ideas why there would be such a significant different in No Deco computations between both computers? Even though they are different brand’s aren’t all dive computers based off the same formula's?

 

[tridacna]

While we are not new to diving we are new to the dive computer world. We started out with basic Suunto Vypers for the first couple years. We just upgraded to Apple Watch Ultra 2/Ocenaic+ this year. We are running both computers together on our dives. We are noticing that the No Deco times are considerably different between the two computers (30+ minute split). While I am not an expert at settings on either device we went in and look at the conservatism/gradient settings on both devices. They are both set at 0 which is the most conservative mode. Any ideas why there would be such a significant different in No Deco computations between both computers? Even though they are different brand’s aren’t all dive computers based off the same formula's?

They are not. This is probably the most discussed issue on SB. Do a search and all will be revealed.

 

[therookie]

Even though they are different brand’s aren’t all dive computers based off the same formula's?

The short answer to that question is a definite no. The long answer - nevermind @tridacna beat me to it.

 

[boulderjohn]

Even though they are different brand’s aren’t all dive computers based off the same formula's?

No, they aren't.

As I understand it from what I read online, the Apple Watch/Oceanic is using the Buhlmann ZHL-16 algorithm, which is commonly used and freely available to computer makers. The Suunto uses their proprietary version of the RGBM algorithm. The Suunto RGBM algorithm is considered extremely conservative, especially on second and third dives. I know how the Suunto sets conservatism, and I know how MOST computers (including mine) set conservatism for Buhlmann, but I don't know how the Apple Watch does it. The website brags that it is a user friendly system, and I suppose that the number 0 is an example of that.

I don't know what you mean by a 30+ minute split. If you are talking about difference in a single dive, then something is wrong. I have dived in groups where some have Suunto and some Buhlmann, and there is nothing like that difference.

 

[butterwm]

No, they aren't.

As I understand it from what I read online, the Apple Watch/Oceanic is using the Buhlmann ZHL-16 algorithm, which is commonly used and freely available to computer makers. The Suunto uses their proprietary version of the RGBM algorithm. The Suunto RGBM algorithm is considered extremely conservative, especially on second and third dives. I know how the Suunto sets conservatism, and I know how MOST computers (including mine) set conservatism for Buhlmann, but I don't know how the Apple Watch does it. The website says it is a user friendly system, and I suppose that the number 0 is an example of that.

I don't know what you mean by a 30+ minute split. If you are talking about difference in a single dive, then something is wrong. I have dived in groups where some have Suunto and some Buhlmann, and there is nothing like that difference.

Thank you so much for this response. So when I say split the Suunto shows 13 minutes to NDL at current depth and the Apple Watch shows 43 minutes for the same depth. Yes, this was noticed on the second dive when my son had to come up a few feet not to exceed his NDL.

To be honest, we went into this Apple Watch thing hoping it would be a backup computer for our Suunto’s. We really like the Apple Watch setup and prefer it greatly over the Suunto. I gusss my biggest concern is since there is a 30 minute split on the NDL if we follow the Apple Watch are we still safe because the Suunto shows up exceeding the limit.

 

[boulderjohn]

So when I say split the Suunto shows 13 minutes to NDL at current depth and the Apple Watch shows 43 minutes for the same depth.

There should not be anything close to this difference. What was the depth, and how long had you been there?

 

[butterwm]

There should not be anything close to this difference. What was the depth, and how long had you been there?

First dive was 81 feet for 43 minutes, 42 minute surface interval and the second dive was 64 feet for 46 minutes. The split was on the second dive.

 

[runsongas]

suunto has a hidden penalty if you do a SI shorter than 1 hour iirc, the procedure when diving multiple computers is to follow whichever one is more conservative though, this is why it is common to match the algorithm or even better match the exact brand/model eg run two shearwaters

 

[KatieMac]

There should not be anything close to this difference. What was the depth, and how long had you been there?

I've had a similar difference on 2nd and 3rd dives - diving with Suunto and Geo.

Ditching them both and getting a Shearwater

 

[Kendall Raine]

I've had a similar difference on 2nd and 3rd dives - diving with Suunto and Geo.

Ditching them both and getting a Shearwater

+1. Good move.