Perdix "Adaptive" Safety Stop - What's the purpose.

[Roy_W]

I'm a little confused as to why you're combining mandatory deco with safety stops. They're two different things for two different types of dive.

The problem lies with the fact that the Perdix is showing me that I have Manadatory Deco stops to do, no confusion here, but it is also showing me a TTS that seems to include the safety stop value .

It is disturbing to see a TTS of 6 mins when I am at 3m and have already completed my mandatory deco stops. I, and SAMMYW above did not think that the TTS would have also included the safety stop time.

 

[Norwegian Cave Diver]

I just realised that it's not easy to read the values in the little squares so I will republish them on order.

As you can see at the 28 minute mark the TTS reads 6 minutes and yet the mandatory Deco's are complete and I am only at 3.5m, it's listing the TTS at 6 minutes and this is why I believe that it is including the Safety Stop in the TTS.

( The mandatory Deco drops to 3 minutes at 3m around the 24 minute mark, I didn't include the image as I don't think its necessary.)

View attachment 666909

Your second screen shot shows you are at 3.5 meters - DECO is NDL of 99 Minutes(you have zero mandatory Deco responsibilities) - your TTS is 6 minutes ( that would be 1 minute for travel to the surface and 5 minutes because you reached 100 feet of depth for your dive). You don't have a mandatory stop but you should do your Safety Stop for two reasons - its a good idea and your computer will be unhappy if you don't. Appreciate what TTS does for you and follow it - plan for it throughout your dive. It is your "All In Number"

 

[Roy_W]

Your second screen shot shows you are at 3.5 meters - DECO is NDL of 99 Minutes(you have zero mandatory Deco responsibilities) - your TTS is 6 minutes ( that would be 1 minute for travel to the surface and 5 minutes because you reached 100 feet of depth for your dive). You don't have a mandatory stop but you should do your Safety Stop for two reasons - its a good idea and your computer will be unhappy if you don't. Appreciate what TTS does for you and follow it - plan for it throughout your dive. It is your "All In Number"

I am trying to get my head around this, does this therefore mean that because I had Safety Stops set to Adaptive and that I had passed 30m, which therefore creates a 5 minutes Safety Stop, that the TTS is simply incorporating my Safety Stop duration as good advice even though not compulsory?

Therefore if I had had the Safety Stop set to OFF, would it just have removed that extra 5 minutes from my final TTS or would it have adjusted and lengthened my Mandatory Deco Stops in order to compensate?

 

[Norwegian Cave Diver]

Yes, a Safety stop is optional - but you shouldn't treat it that way. Do every minute of every SS. If that means 3 minutes or 5 minutes. Set your computer - if you wish - to do all SS and Deco stops at 20 feet/6 Meters. Turn off that Adaptive choice. Now every dive will ask you to stop at 20 feet/6 meters. TTS should be easy to understand. At depth - What does my TTS say? - What is my depth? What will my travel time be to the surface based upon my depth and expected accent rate? Subtract that from your TTS and you will know what SS and/or Deco stop time will be.
Do a simple dive and test it. 20 meters max depth (not near 100 feet so a 5 minute SS is required).

Check your wording in your second paragraph. It's confusing. "Safety Stop and Mandatory Safety Stop".
No such thing as a Mandatory SS. Yes your Shearwater will be unhappy that you ignored a SS.

 

[scubadada]

Hi @Roy_W

Most of my dives are no stop but about 5% are light deco. I leave the computer in rec mode with a 3 min SS. I use SurfGF to determine the length of my SS or to pad my deco in order to surface with the desired GF. I do a minimum SS of 3 minutes, regardless. Works well for me

 

[Roy_W]

Mandatory Deco Stops

Check your wording in your second paragraph. It's confusing. "Safety Stop and Mandatory Safety Stop".
.

Mea Culpa, I have corrected the sentence to read Mandatory Deco Stop.... ( Thanks for pointing that out).

 

[mc42]

According to the manual, in OC Rec mode, the TTS includes mandatory deco, ascent, and safety stop time, so that does explain what’s happening with the extra 5/6 minutes.

In a sense, when in OC Rec mode, the computer is working the most conservative route, which includes all deco and safety stops. In OC Tec, there is no concept of safety stops.

 

[Stoo]

Maybe my question should have been , do you follow the computers advice to do a safety stop "after" the completion of the mandatory or do you just ignore it...

I do. My SWs are in tech mode, but they have a countdown timer after deco clears, so I typically add on 3 - 5 minutes "extra". I'm old, have lots of aches and pains, dive in frigid water most of the time and basically have a number of things going on which could make me susceptible to getting bent. Almost all of my dives are in the 110'-160' range, and many deeper than that. I guess I figure that hanging out for a few minutes longer just makes sense. I can't honestly say that I have never bailed as soon as my mandatory deco cleared. Usually if I do that, it's bladder related. I've never been bent when I did this.

Along the same lines, I'm also a big believer in "quiet time" following a big dive. I like to sit quietly, post deco-dive before hauling tanks etc. I consider this a continuation of my "elective decompression".

 

[rsingler]

According to the manual, in OC Rec mode, the TTS includes mandatory deco, ascent, and safety stop time, so that does explain what’s happening with the extra 5/6 minutes.

It's funny how long it took to get the actual answer to the OP's question.

 

[Blackcrusader]

It's funny how long it took to get the actual answer to the OP's question.

It is good others know how their Perdix works. I spent a lot of time reading the manuals a few times so I would not be lost on how mine works. I never found the TTS to be confusing.