Can someone please explain how Shearwater computers do deco?

[bencaha]

Hey guys! I have now done about 40 dives on my Tern TX and went into deco (?) with it for the first time. Well at least that's what the computer said during the dive. I didn't have to do an extended deco stop though as it cleared up during the ascent. In the beginning it stated 2 minutes at 6 meters though. Can someone please explain how exactly the algorithm works once i enter deco? I also dive with surface GF on my screen so I monitor where I am at anyways, but I somehow expected the computer to just stop me at a certain depth without taking into account any off gassing I did during the ascent. It seems like Shearwater computers are smarter than I originally expected and I can adjust how I plan my dives with the NDL of the computer accordingly.

 

[lowwall]

There's no hard rules about what happens after you trigger a deco stop. Instead, deco obligations are constantly recalculated based on your current tissue loadings and the assumption of a direct ascent at 10m/minute to the surface from your current depth.

If your ascent is slow enough to clear whichever tissue triggered the deco stop requirement before you hit the announced stop depth, it will clear the deco obligation. Of course, if your ascent is delayed or too slow, you can also see increases in your deco obligation.

 

[bencaha]

Any deco obligation is based on the assumption of a direct ascent at 33' (10m) per minute to the surface from your current depth. This is constantly recalculated, so If your ascent is slow enough to clear that particular tissue before you hit the stop depth, it will clear the deco obligation. Of course, if your ascent is too slow when you are still deep, it may actually increase your deco obligation.

Makes sense. Assume I accumulate more deco, will the computer start putting in stops at different depths or does Shearwater always calculate with a stop at 6 meters?

 

[lowwall]

Makes sense. Assume I accumulate more deco, will the computer start putting in stops at different depths or does Shearwater always calculate with a stop at 6 meters?

Yes it will put in whatever additional stops are needed if you don't do an immediate ascent once you incur the initial obligation. Check the computer regularly.

I was editing my post while you responded, so it's also answered above.

 

[rongoodman]

Depending on the inert gas load it will add more stops and time as necessary.

 

[bencaha]

Thanks for all the replies. Answered my question perfectly and cleared up all the confusion I had during and after the dive. I'd consider this thread closed!

 

[lowwall]

Thanks for all the replies. Answered my question perfectly and cleared up all the confusion I had during and after the dive.

Happy to help. Thanks for the feedback.

I'd consider this thread closed!

You must be new around here

 

[JMarc]

Makes sense. Assume I accumulate more deco, will the computer start putting in stops at different depths or does Shearwater always calculate with a stop at 6 meters?

Depending on how you set it up, the shallowest stop is at 3 or 6m. Then you may get additional stops every 3m.

You get deeper stops if you can't go shallower without risking DCS.

Note that if you go into deco, you better ensure that you have enough gas to do the stops and handle unexpected events. Note also that if stop time starts by accumulate slowly, after a time it does so quickly enough that planning and staying on plan is really needed. That should be covered in your training. If you weren't trained for that, avoid going into mandatory deco until you are.

 

[bencaha]

Happy to help. Thanks for the feedback.


You must be new around here

Not really roo new. I expect it to go on, but the inital question is answered haha

 

[bencaha]

Depending on how you set it up, the shallowest stop is at 3 or 6m. Then you may get additional stops every 3m.

You get deeper stops if you can't go shallower without risking DCS.

Note that if you go into deco, you better ensure that you have enough gas to do the stops and handle unexpected events. Note also that if stop time starts by accumulate slowly, after a time it does so quickly enough that planning and staying only plan is really needed. That should be covered in your training. If you weren't trained for that, avoid going into mandatory deco until you are.

Thanks for the additional detail! I try to dive within the NDL so I don't run into any issues. If I expect more time spent at deeper depths I plan accordingly.