Tusa TC1 (Crest CR-4) Crazy? NOT working algorithm?

[Sammy9382]

So I think this Tusa TC1 is a bit crazy.

I went to 42m. After 13 minutes or so I go into deco. Makes sense. It tells me to go to 9m. I slowly do that. While doing that it gives me about 1 minute extra deco for every meter or so going up, even when close to 9 meters. Seems weird, but maybe possible. So after 47min and an ascent to 10m I have 37min deco. Then it counts 3m or so to stay at 9am. All good with that. Then it says to go the 5m. All good with that. In the mean time it keeps adding deco. Total of 51 minutes (!!!) after 62min. Makes no sense. My buddy had ZERO deco. Then at 5m it ALWAYS tells me to do a stop of 5min. I do that and then it says clear. mmmm, what happened the (way to high) 30 minutes of deco now? Just gone? makes no sense, or? Sounds like the computer has no algorithm, or it has, but it shows other numbers. Any ideas?

 

[lowwall]

Way back when the Deep 6 version of this computer was introduced and still used essentially the same software as the original Crest, one of the members here did some simulated dives using a pressure pot to document the data display once you got into deco. Unfortunately, that thread veered off and got pulled.

But what I remember was that it was very confusing and did not follow anything we are used to from other computers. I probably have this wrong, but I think the minutes displayed under DECO are elapsed time since you first exceeded NDL. Once you ascended to the requested ceiling, DECO would be replaced by STOP and it would revert to a countdown for that stop. After the stop was complete, if you were still in deco it would go back to the elapsed time until you got to the next ceiling. The manual at the time did not fully describe what was going on so even a motivated user couldn't know what they would be facing.

The justification for showing elapsed time instead of something like total time to surface was that this was never intended as a deco computer and that the display was intended only to get a diver who inadvertently dipped into deco out of the water when they did eventually look at the computer.

Fixing this was a major motivation for Deep 6 to develop their own software for the computer.

 

[Sammy9382]

Way back when the Deep 6 version of this computer was introduced and still used essentially the same software as the original Crest, one of the members here did some simulated dives using a pressure pot to document the data display once you got into deco. Unfortunately, that thread veered off and got pulled.

But what I remember was that it was very confusing and did not follow anything we are used to from other computers. I probably have this wrong, but I think the minutes displayed under DECO are elapsed time since you first exceeded NDL. Once you ascended to the requested ceiling, DECO would be replaced by STOP and it would revert to a countdown for that stop. After the stop was complete, of you were still in deco out would go back to the elapsed time until you got to the next ceiling. The manual at the time did not fully describe what was going on so even a motivated user couldn't know what they would be facing.

The justification for showing elapsed time instead of something like total time to surface was that this was never intended as a deco computer and that the display was intended only to get a diver who inadvertently dipped into deco out of the water when they did eventually look at the computer.

Fixing this was a major motivation for Deep 6 to develop their own software for the computer.

Thank you so much. Your description sounds spot on. From the pics you can actually "calculate" the minutes displayed under Deco is indeed exactly the elapsed time after exceeding NDL. And indeed DECO is replaced by STOP after reaching the ceiling. I did not post a pic of that in my thread, but here it is.

Obviously this is not usefull, as you do not know how much your deco is until you reach the ceiling. Quite dangerous, as you can not manage your air accordingly. You bascially have to go to the ceiling "as fast as possible" (well, not too fast) and hope and pray you have enough air to do the deco stop. You explained it all, as you said this was not intended as deco computer.

 

[dmaziuk]

Careful, if you criticize that computer too much the Almighty Mods will forever ban you from saying its name ever again. Ask me how I know.

As I recall they also mentioned "additional safety measures" programmed into the computer, and never admitted to what those might be, exactly, nor why.

 

[tursiops]

OP, you assumed you knew how the computer worked and what its display meant.. You didn't.
The manual (attached) is not good but ought to be read.
What thing it says is don't do deco diving with this computer.

 

[tursiops]

Way back when the Deep 6 version of this computer was introduced and still used essentially the same software as the original Crest, one of the members here did some simulated dives using a pressure pot to document the data display once you got into deco. Unfortunately, that thread veered off and got pulled.

That thread was not pulled, just closed. here is a post in it that describes how the display show mionutes past NDL, not minutes of DECO required. https://scubaboard.com/community/threads/thoughts-on-deep-6s-new-dc.588937/post-9129056

 

[lowwall]

That thread was not pulled, just closed. here is a post in it that describes how the display show mionutes past NDL, not minutes of DECO required. https://scubaboard.com/community/threads/thoughts-on-deep-6s-new-dc.588937/post-9129056

Thank you for finding this. The pressure pot dive with photos starts here: https://scubaboard.com/community/threads/thoughts-on-deep-6s-new-dc.588937/post-9029082

I do want to note that this was an earlier version of the Crest software that may or may not match what you have. It definitely does NOT match the current Deep 6 software.