Hammerhead 10 Foot Stop Elimination?

**JPJones** · 2nd March 2006, 13:49

If you keep your PO2 at or above your setpoint all but the last minute of the 10 ft stop clears fine. But sometimes that last minute won't clear till your pass 10ft but it always clears as you pass 10ft. Since it is consistant in how it works after I have done the minute I go up and watch it clear as I pass 10 ft. This is not the first computer I have had that acted this way so it never bothered me.

I normally do my last stop at 15ft when I'm in salt water because of the surge .

***ScubaDadMiami*** · 2nd March 2006, 15:49

I'll be flapping my wing, er, arm this coming weekend to see what happens.

Thanks for the suggestions.

**UWSojourner** · 2nd March 2006, 17:02

Quote: (Originally Posted by jradomski)

Remember we are talking about real time.. when you build tables, when a stop is clear (or your limits for that depth have been reached) it jumps to the next stop and the current gf is recalculated.. The current GF limit is based on the current depth..

The ascent is "clear" to the next stop based on the current GF limit..

when you clear a "stop" all it means is that upon reaching the next level you wount violate that limit..

Say you have a LoGF=10 and a HiGF=100 and you hit your LoGF at 90ft. Then your 20ft GF is 80, your 10ft is 90, and surfacing GF is 100.

What has to happen for your computer to allow you to go to 10ft?

And if you stay at 20ft, what has to happen for it to clear completely?

***jradomski*** · 2nd March 2006, 17:17

Quote: (Originally Posted by UWSojourner)

Say you have a LoGF=10 and a HiGF=100 and you hit your LoGF at 90ft. Then your 20ft GF is 80, your 10ft is 90, and surfacing GF is 100.

What has to happen for your computer to allow you to go to 10ft?

And if you stay at 20ft, what has to happen for it to clear completely?

if you stay at 20 it will clear completely when the gf computed for that depth is reached... if the gflimit was 80 at 20fsw thats when it will clear, to move the limits up you have to be at that depth for that limit to be imposed..

I don't know if this has changed but I know originally the HH used a workman implementation, this doesnt directly support using GF so the numbers have to get approximated.. GF actually works directly on the A and B coefficients..

**UWSojourner** · 2nd March 2006, 17:47

Quote: (Originally Posted by jradomski)

if you stay at 20 it will clear completely when the gf computed for that depth is reached... if the gflimit was 80 at 20fsw thats when it will clear, to move the limits up you have to be at that depth for that limit to be imposed..

I don't know if this has changed but I know originally the HH used a workman implementation, this doesnt directly support using GF so the numbers have to get approximated.. GF actually works directly on the A and B coefficients..

So, at 10ft it clears me when my tissue compartment's GF reaches 90? Then, you may surface at a GF > 100 even though you specified the HiGF = 100?

***jradomski*** · 2nd March 2006, 18:23

Quote: (Originally Posted by UWSojourner)

So, at 10ft it clears me when my tissue compartment's GF reaches 90? Then, you may surface at a GF > 100 even though you specified the HiGF = 100?

no its LESS...

you dont clear until you get (down) to 90% instead of 100%

**UWSojourner** · 2nd March 2006, 18:57

Quote: (Originally Posted by jradomski)

no its LESS...

you dont clear until you get (down) to 90% instead of 100%

Then you must be calculating the tissue compartment's GF assuming the diver is at the surface, but holding them at 10ft based on the max GF for that depth?

***jradomski*** · 2nd March 2006, 19:16

Quote: (Originally Posted by UWSojourner)

Then you must be calculating the tissue compartment's GF assuming the diver is at the surface, but holding them at 10ft based on the max GF for that depth?

I HAVEN NOT see the code but from my experience with the unit and some assumptions that I'm making based on my experience with coding a real time GF, is that the allowable limit are being reduced by the current depth so that the limit is actually skewed downward by being deeper..

The projected ascent should be correct because its "stepping" through the dive, but the "real time" limit is atually more conservative unless you are at the correct depth..

Usually the GF is programmed in a way so that all the other terms drop off when depth is zero leaving the GF high.. but in real time the GF high may not actually be the surfacing value but forced to clear at the last stop limit (being actually more conservative)

**UWSojourner** · 2nd March 2006, 22:08

Well, FWIW the new Meg electronics won't behave that way ... so that's something to look forward to.

... and realtime or not, the electronics should be able to look at the next depth for BOTH the diver's TC GFs and Baker's max GFs. If it did, I don't think the problems discussed here would be there.

***jradomski*** · 3rd March 2006, 12:06

Quote: (Originally Posted by UWSojourner)

Well, FWIW the new Meg electronics won't behave that way ... so that's something to look forward to.

... and realtime or not, the electronics should be able to look at the next depth for BOTH the diver's TC GFs and Baker's max GFs. If it did, I don't think the problems discussed here would be there.

I hope thats not the case.. The way it appears its implemented on the HH has more benefits than negatives..

I HAVE coded it both ways and definately prefer a truely sliding GF based on current depth (rarther than a strict look ahead based hard stepped implementation).. Its more flexible especially if any of the short deep stops are skipped to get back onto the projected schedule..

Its not my job to tell the manufacturers the pluses and minuses of different implementations.. I did my homework, they should do theirs.. A DC manufacturer should be more concerned with what the consequences are if the diver screws up rather than when things are done perfectly.. A few minutes extra deco wont hurt you, not enough will...

maybe some extra checking should be added when you are at the last stop depth before clearing to the surface, but still base it on your depth not a projected depth.. The info IS correct once you reach that projected depth...

2nd March 2006, 13:49	#21 (permalink)
JPJones O2ptima Test Dummy Current Rebreather/s: Inspiration Classic Megalodon Sport Kiss Classic Kiss Optima Titan Other Rebreather/s: Join Date: Sep 2005 Location: Florida Posts: 367	Re: Hammerhead 10 Foot Stop Elimination? If you keep your PO2 at or above your setpoint all but the last minute of the 10 ft stop clears fine. But sometimes that last minute won't clear till your pass 10ft but it always clears as you pass 10ft. Since it is consistant in how it works after I have done the minute I go up and watch it clear as I pass 10 ft. This is not the first computer I have had that acted this way so it never bothered me. I normally do my last stop at 15ft when I'm in salt water because of the surge . __________________ NSS/CDS Training Chairman www.jpjscuba.com
(Offline)

2nd March 2006, 15:49	#22 (permalink)
*ScubaDadMiami* Moderator Current Rebreather/s: Optima Other Rebreather/s: Join Date: Sep 2005 Location: Florida, USA Posts: 2,132	Re: Hammerhead 10 Foot Stop Elimination? I'll be flapping my wing, er, arm this coming weekend to see what happens. Thanks for the suggestions. __________________ Howard Packer IANTD CCR Instructor Miami Beach, Florida CCRDiveTraining.com
(Offline)

2nd March 2006, 17:02	#23 (permalink)
UWSojourner Pacific Northwest Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Location: Portland Oregon Posts: 556	Re: Hammerhead 10 Foot Stop Elimination? Quote: (Originally Posted by jradomski) Remember we are talking about real time.. when you build tables, when a stop is clear (or your limits for that depth have been reached) it jumps to the next stop and the current gf is recalculated.. The current GF limit is based on the current depth.. The ascent is "clear" to the next stop based on the current GF limit.. when you clear a "stop" all it means is that upon reaching the next level you wount violate that limit.. Say you have a LoGF=10 and a HiGF=100 and you hit your LoGF at 90ft. Then your 20ft GF is 80, your 10ft is 90, and surfacing GF is 100. What has to happen for your computer to allow you to go to 10ft? And if you stay at 20ft, what has to happen for it to clear completely?
(Offline)

2nd March 2006, 17:17	#24 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Home Build Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Home Build Join Date: Mar 2005 Location: "Da" Bronx Posts: 3,011	Re: Hammerhead 10 Foot Stop Elimination? Quote: (Originally Posted by UWSojourner) Say you have a LoGF=10 and a HiGF=100 and you hit your LoGF at 90ft. Then your 20ft GF is 80, your 10ft is 90, and surfacing GF is 100. What has to happen for your computer to allow you to go to 10ft? And if you stay at 20ft, what has to happen for it to clear completely? if you stay at 20 it will clear completely when the gf computed for that depth is reached... if the gflimit was 80 at 20fsw thats when it will clear, to move the limits up you have to be at that depth for that limit to be imposed.. I don't know if this has changed but I know originally the HH used a workman implementation, this doesnt directly support using GF so the numbers have to get approximated.. GF actually works directly on the A and B coefficients.. __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
(Offline)

2nd March 2006, 17:47	#25 (permalink)
UWSojourner Pacific Northwest Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Location: Portland Oregon Posts: 556	Re: Hammerhead 10 Foot Stop Elimination? Quote: (Originally Posted by jradomski) if you stay at 20 it will clear completely when the gf computed for that depth is reached... if the gflimit was 80 at 20fsw thats when it will clear, to move the limits up you have to be at that depth for that limit to be imposed.. I don't know if this has changed but I know originally the HH used a workman implementation, this doesnt directly support using GF so the numbers have to get approximated.. GF actually works directly on the A and B coefficients.. So, at 10ft it clears me when my tissue compartment's GF reaches 90? Then, you may surface at a GF > 100 even though you specified the HiGF = 100?
(Offline)

2nd March 2006, 18:23	#26 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Home Build Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Home Build Join Date: Mar 2005 Location: "Da" Bronx Posts: 3,011	Re: Hammerhead 10 Foot Stop Elimination? Quote: (Originally Posted by UWSojourner) So, at 10ft it clears me when my tissue compartment's GF reaches 90? Then, you may surface at a GF > 100 even though you specified the HiGF = 100? no its LESS... you dont clear until you get (down) to 90% instead of 100% __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated. Last edited by jradomski : 2nd March 2006 at 18:30.
(Offline)

2nd March 2006, 18:57	#27 (permalink)
UWSojourner Pacific Northwest Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Location: Portland Oregon Posts: 556	Re: Hammerhead 10 Foot Stop Elimination? Quote: (Originally Posted by jradomski) no its LESS... you dont clear until you get (down) to 90% instead of 100% Then you must be calculating the tissue compartment's GF assuming the diver is at the surface, but holding them at 10ft based on the max GF for that depth?
(Offline)

2nd March 2006, 19:16	#28 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Home Build Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Home Build Join Date: Mar 2005 Location: "Da" Bronx Posts: 3,011	Re: Hammerhead 10 Foot Stop Elimination? Quote: (Originally Posted by UWSojourner) Then you must be calculating the tissue compartment's GF assuming the diver is at the surface, but holding them at 10ft based on the max GF for that depth? I HAVEN NOT see the code but from my experience with the unit and some assumptions that I'm making based on my experience with coding a real time GF, is that the allowable limit are being reduced by the current depth so that the limit is actually skewed downward by being deeper.. The projected ascent should be correct because its "stepping" through the dive, but the "real time" limit is atually more conservative unless you are at the correct depth.. Usually the GF is programmed in a way so that all the other terms drop off when depth is zero leaving the GF high.. but in real time the GF high may not actually be the surfacing value but forced to clear at the last stop limit (being actually more conservative) __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
(Offline)

2nd March 2006, 22:08	#29 (permalink)
UWSojourner Pacific Northwest Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Location: Portland Oregon Posts: 556	Re: Hammerhead 10 Foot Stop Elimination? Well, FWIW the new Meg electronics won't behave that way ... so that's something to look forward to. ... and realtime or not, the electronics should be able to look at the next depth for BOTH the diver's TC GFs and Baker's max GFs. If it did, I don't think the problems discussed here would be there.
(Offline)

3rd March 2006, 12:06	#30 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Home Build Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Home Build Join Date: Mar 2005 Location: "Da" Bronx Posts: 3,011	Re: Hammerhead 10 Foot Stop Elimination? Quote: (Originally Posted by UWSojourner) Well, FWIW the new Meg electronics won't behave that way ... so that's something to look forward to. ... and realtime or not, the electronics should be able to look at the next depth for BOTH the diver's TC GFs and Baker's max GFs. If it did, I don't think the problems discussed here would be there. I hope thats not the case.. The way it appears its implemented on the HH has more benefits than negatives.. I HAVE coded it both ways and definately prefer a truely sliding GF based on current depth (rarther than a strict look ahead based hard stepped implementation).. Its more flexible especially if any of the short deep stops are skipped to get back onto the projected schedule.. Its not my job to tell the manufacturers the pluses and minuses of different implementations.. I did my homework, they should do theirs.. A DC manufacturer should be more concerned with what the consequences are if the diver screws up rather than when things are done perfectly.. A few minutes extra deco wont hurt you, not enough will... maybe some extra checking should be added when you are at the last stop depth before clearing to the surface, but still base it on your depth not a projected depth.. The info IS correct once you reach that projected depth... __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
(Offline)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode