No stop limit vs. No stop time remaining

[RXTdiver]

In the PADI Open Water Course where they are talking about dive computers, there is a part where they tell about the types of information that a dive computer displays.

1. No stop (no decompression) limits
2. Depth
3. Elapsed time
4. No stop time remaining
5. Ascent rate
6. Emergency decompression
7. Previous dive information

What is the difference between no stop limit (#1) and no stop time remaining (#4)?

During this course, they seem to use no stop limit and no stop time interchangeably.

 

[inquis]

NS Remaining = NS Limit - Dive Time

Prior to the dive, Dive Time = 0, so NS Remaining would be equal to NS Limit in that case.

 

[Brett Hatch]

Agree with inquis on the definition of these 2 numbers, that's exactly right.

One other thing about how they are used. The "no-stop limit" is an estimate of the maximum amount of time you can dive to a given depth, assuming a square profile. That is, assuming you descend directly to your bottom depth, hang out down there for X number of minutes, and then ascend at a certain rate, possibly with a safety stop built into the definition.

When you do a dive with a modern computer, a perfectly square profile might be a pessimistic estimate of your actual dive. If you spend a significant amount of time shallower than the planned depth, your computer will give you credit for that, and the sum of your dive time + no-stop time remaining may exceed the no-stop limit you estimated before your dive. This is called multi-level diving, and one of the big advantages of using a PDC is that you will end up with longer dive times for multi-level dives, because it takes into account the depth that your PDC (and your body) actually experience.

Hope this helps, cheers.

 

[Jeff_O]

There probably is something in some new computers, that also give I expect an estimate of time left based on air consumption. But I expect changes like depth, thermoclines, currents.... could heavily change when air would run out.

With an 80cf main tank, I also used to use a 13cf pony bottle and separate reg. Now it has use in fresh water rinse to keep water out of where it should not be. A large rubber maid bin works fine for rinsing gear.

Mostly I have been diving more recently in shallow water around 25 to 35 feet, so my old puck timer and puck computer are sufficient.

 

[johndiver999]

I would explain it as.. the computer won't display all that information at one time. Some information is provided before the dive and some during the dive.

The no stop limits will be provided before a dive and help you plan. For example it might say your limit is 60 minutes at 70 feet and 50 minutes at 80 feet and so on. This is how long you can dive without going into decompression. It depends on the gas you are using and if you have left over nitrogen from earlier dives.

During an actual dive, the computer will tell you exactly how many minutes you can REMAIN at your current depth without incurring a decompression penalty. This is essential a count down clock that will approach zero as your dive continues. This is the no stop remaining time.

 

[CT-Rich]

There probably is something in some new computers, that also give I expect an estimate of time left based on air consumption. But I expect changes like depth, thermoclines, currents.... could heavily change when air would run out.

With an 80cf main tank, I also used to use a 13cf pony bottle and separate reg. Now it has use in fresh water rinse to keep water out of where it should not be. A large rubber maid bin works fine for rinsing gear.

Mostly I have been diving more recently in shallow water around 25 to 35 feet, so my old puck timer and puck computer are sufficient.

I had an Aeris 300Ai that used your current air consumption to give you an estimated dive time remaining. It was kind of a cool function at the time and I used quite a bit because it gave me a measure of how much time I would be able to finish a bottom traverse underwater. When that computer died, I replaced it with a gauge and wrist computer. I don't know if that is feature still found on air integrated computers.

 

[tursiops]

During this course, they seem to use no stop limit and no stop time interchangeably.

That is because they mean the same thing. Note that no stop time and no stop time remaining are NOT the same thing; the latter is reduced by your dive time spent so far.

 

[Outbound]

I had an Aeris 300Ai that used your current air consumption to give you an estimated dive time remaining. It was kind of a cool function at the time and I used quite a bit because it gave me a measure of how much time I would be able to finish a bottom traverse underwater. When that computer died, I replaced it with a gauge and wrist computer. I don't know if that is feature still found on air integrated computers.

I have my Teric set up to display my GTR: gas time remaining. It’s based on my gas consumption rate at the moment and whatever I set my reserve to.

 

[Belzelbub]

In the PADI Open Water Course where they are talking about dive computers, there is a part where they tell about the types of information that a dive computer displays.

1. No stop (no decompression) limits
2. Depth
3. Elapsed time
4. No stop time remaining

I don't expect that you'll see both No Stop (No Deco) Limits and No Stop time remaining during a dive. That would be confusing.
Most computers have a plan feature where you can see what the No Stop Limit (commonly referred to as NDL) for given depths. This will vary between dive 1 and subsequent dives as the plan function during a surface interval will take into account the previous dive(s).

During a dive, No Stop Time remaining, or time to NDL would be displayed. This will show how much time you have left at the current depth before incurring a mandatory decompression obligation. This will take into account the depth and time up to that point, then assume depth remains constant. When you are doing your checkout dives, you can see this number rise when you ascend.

During this course, they seem to use no stop limit and no stop time interchangeably.

Yep. You'll also hear No Deco Limit or NDL. They are the same.

There probably is something in some new computers, that also give I expect an estimate of time left based on air consumption. But I expect changes like depth, thermoclines, currents.... could heavily change when air would run out.

Yes, absolutely. In the implementations I'm familiar with, the computer calculates the change in tank pressure, and uses this to predict how long you can remain at the current depth. On my computers, it takes into account recent breathing rate for this calculation. It can't predict what's coming next, but uses a time frame to provide a best prediction.

 

[RXTdiver]

I have my Teric set up to display my GTR: gas time remaining. It’s based on my gas consumption rate at the moment and whatever I set my reserve to.

Do you use GTR instead of using remaining no stop time or do you use both?