Hollis TX1 verses Mares Puck

[NDSquirrel]

I was lucky enough to win an Hollis TX1 as a door prize. I know the DC is more capability than I currently need because I do not plan on diving on trimix any time soon. Still I have been using the DC as my second DC during normal recreational dives. My primary DC is a Mares Puck. On a recent dive I had the Hollis yell at me because I broke NDL however the Mares reported I was still within NDL. Since then I started writing down the desat time each computer report after the dive. I noticed that after the first dive of the day, the two DCs are within minutes of each other in the desat time. However after the second and subsequent dives on the same day, the two DC diverge by hours. Usually it seems that the Hollis desat time doubles but the Mares only adds 3-5 hours to the desat time.

I realize that the two DC use different algorithms. Hollis uses Bühlmann ZHL-16C and Mares uses RGBM (Reduced Gradient Bubble Model)-algorithm. Can anyone explain to me why such a divergence after the second dive?

I have been adjusting the Hollis GF setting to try to align the NDL times with the Mares. I believe the Mares Puck with SF-0 uses 30-85 GF. On the second dive the NDL are relatively close with Hollis set to 30-85; however changing the GF setting on the Hollis does not bring the two DC any closer in desat time. Because the Hollis has such a higher residue Nitrogen the NDL times for any 3rd dive are not close regardless of GF settings.

 

[Remy B.]

if you wait enough you probably will hear from some members that you don't know how to operate your dive puter, and that you need only one regardless of that you got lucky and got an extra one for free and that you are using it as backup just in case the other fails.

I had the same problem with my Punk Pro and my Suunto D4i novo, they were not exactly tracking the same, taken that both had the standard setting from factory P0A0 for the Punk Pro and P0A0 for the D4i, what I believe it happen with my puters is that by mistake I went a click too far and enter the dive as a Nitrox dive on the Suunto in my first five of a series of 4 divided in 2 days, that locked me on Nitrox for the rest of my other dives in Nitrox mode, I did follow the manual and put the nitrox % to 21 so it calculates as air even if you are in nitrox mode for the rest of the dives.

I did dive previosly with the two puters and did not had a problem, but in those oportunities I enter with Air mode and had not gone deeper than 26m, when I made the mistake to enter in Nitrox mode in my first dive this time, both puters were tracking very close, that was a dive at 22m, second dive of the day they were tracking not so close but close enough, as well here I already had saw my mistake and set the nitrox to 21% , but we went a little deeper 24m, always stayed in NDL.

Since Suunto locks your puters if you do a Nitrox dive first and until the No fly is not gone it will not show you the Air mode, I did dive the next day as well with both at 21%, but the first dive was at 36m to see a little wreck, we begin to ascent to stay in our NDL but the Punk Pro was not adding that fast NDL time, while the suunto did, I enter in Deco on my Punk Pro, while I had as much as 23min if I remember right of difference in time between the two.

the puters did what ever the magic boxes do, what got them to do what they calculated I don't know, either it was my mistake of entering my first dive in Nitrox 32 mode with the Suunto, that took those calculations and give out those results, or that I did my second dive of the first day was a little deeper and the Punk Pro give out those calculations, normally your first dive is the deep one, so maybe that throw off the Punk Pro.

the DM that was my guide had a Mares Smart, apparantly he never enter Deco or at least he did not tell me if he did, so assuming that he didn't you have 3 puters with different results.

I don't know how far Suunto customize their algorhitm or Mares does, I do follow my Punk Pro, since it is my first DC and use the Suunto as backup, it happen in this time that the Punk Pro is more conservacionist than the Suunto, and as it is suggested you follow the one that keeps you safer.

Check if that is not what happen with you, check your logs and see if everything was the same as far as P0A0's and mixes.

 

[NDSquirrel]

I checked the logs and both computers were programmed for air

 

[Remy B.]

Ok, your personal settings and altitude on both were equal as well ? On the Mares it will show P0 ( standard factory setting ) A0 ( altitude "cero" ), on the Hollis TX1, I guess it will be something like that as well.

If for example you have set one puter to P2A0 and the other on P0A0, the one with the P2 will enter in Deco faster, there for they will have big differences in NDL.

it appear all brands of DC seems to have their settings a little different between them or even between models from the same manufacturer.

Look what happen in my case 2 puters from the same brand and 1 from another, all three with different results.

As all manuals state a DC is not substitude for training, and in training you will see the tables, if you follow to the letter on your dive plan and do square profiles, you probably will gain more NDL with the table, but don't take my word for it, as I'm far from been knowlegeble on Diving, you can see that you have more dives than I do, I only can share what happen in my case, I do some reading and have follow some experts with neutral perspectives and very educated answers here in SB, and is what I have understood from both.

I don't think neither DC will hurt you, taken you are in normal fit conditions and in normal diving conditions as well, and that you follow the DC.