Sheerwater vs VR3 for an EVO 4th cell?

**Gill Envy** · 13th February 2007, 19:58

I've been won over to the concept that a totally independent 4th cell driven po2 and deco computer would be the single most valuable modification to our Evolutions, and pretty much any eCCR.

I want to hear from users of VR3's and Sheerwater's about their reasons for recommending one or the other for this application. Any details on build quality issues, deco algorithms match with the Vision and any other incedentals would be great.

The warrenty is soon to run out on our evo's, and after a year of diving them as designed, i'm getting ready to make a change or two, your insights would be most appreciated.

divetheworld · 13th February 2007, 20:19

The Shearwater connects in parallel with your existing three to give on-line PO2 and (GF)deco.

Advantages;
no need for an extra cell
Runs on Gradient Factors like you Vision.
Gives mV display of cells at anytime
User configurable Auto setpoint switching (up/down/both)
No pin numbers to release He mixes

And here is the big one - 5 closed circuit and 5 seperate open circuit gas lists. When you bail out (4 push buttons) it changes gas lists and therefore look ahead deco without fuss.

**Gill Envy** · 13th February 2007, 21:03

Ok, the claim has been made that anything short of a totally endependent cell could be vulnerable to upstream voltage irregularities from the primary...due to water ingress, battery bounce or any other of the long list of remote, but possible failures a primary on any rebreather might have. I don't know of any examples to point to where this happened but in theory it has some merrit. Your thoughts?

It's my understanding that the sheerwater better matches the vision for deco through a similar gradient factor and a more continuious decompression calculation...whereas the VR3 requires exact deco stops or you don't get credit.

corrections?

Quote: (Originally Posted by divetheworld)

The Shearwater connects in parallel with your existing three to give on-line PO2 and (GF)deco.

Advantages;
no need for an extra cell
Runs on Gradient Factors like you Vision.
Gives mV display of cells at anytime
User configurable Auto setpoint switching (up/down/both)
No pin numbers to release He mixes

And here is the big one - 5 closed circuit and 5 seperate open circuit gas lists. When you bail out (4 push buttons) it changes gas lists and therefore look ahead deco without fuss.

divetheworld · 13th February 2007, 21:11

Quote: (Originally Posted by Gill Envy)

Ok, the claim has been made that anything short of a totally endependent cell could be vulnerable to upstream voltage irregularities from the primary...due to water ingress, battery bounce or any other of the long list of remote, but possible failures a primary on any rebreather might have. I don't know of any examples to point to where this happened but in theory it has some merrit. Your thoughts?

It's my understanding that the sheerwater better matches the vision for deco through a similar gradient factor and a more continuious decompression calculation...whereas the VR3 requires exact deco stops or you don't get credit.

corrections?

From what I remember, and I'm sure Bruce will correct any errors, the Shearwater doesnt use only one cell for its calculations. If one cell is out of expected range, then it is removed from the decision making process and that cell PO2 display is flashing to indicate the irregularity. It must have two similar to compare, if it does not then it defaults to 0.0 PO2 and gives a low PO2 alarm.
Better than a fourth cell? I think so. There are limits to all systems of this type but once you follow one philosophy, you have to make it work in all forseeable circumstances. For a 3 cell GF computer, I think this is acheived when you include the HUD in the package.
If your backing up a vision, there are limits to the amount of redundancy required and I think that any more than this is paranoia!

**Gill Envy** · 13th February 2007, 21:51

Quote: (Originally Posted by divetheworld)

From what I remember, and I'm sure Bruce will correct any errors, the Shearwater doesnt use only one cell for its calculations. If one cell is out of expected range, then it is removed from the decision making process and that cell PO2 display is flashing to indicate the irregularity. It must have two similar to compare, if it does not then it defaults to 0.0 PO2 and gives a low PO2 alarm.

If I understand it correctly the Sheerwater has no audible alarms but can be fitted with an HUD. If I understand correctly, it is also capable of running off one cell like a VR3.

Quote: (Originally Posted by divetheworld)

Better than a fourth cell? I think so. There are limits to all systems of this type but once you follow one philosophy, you have to make it work in all forseeable circumstances. For a 3 cell GF computer, I think this is acheived when you include the HUD in the package.
If your backing up a vision, there are limits to the amount of redundancy required and I think that any more than this is paranoia!

while the vision has quite a bit of redundancy, I have tracked two known vulnerabilities that make me feel that a totaly isolated po2 system is justifieable (though it seems justifiable on any rebreather):

1. it has one screen, if that one screen malfunctions, you have much of your info in that one basket...the HUD does help, but requires back up deco. My thinking is, if i'm going to get a back up po2 computer i might as well get one that also has deco.

2. while the electronics have redundancy, they have a common failure point. there is more than one case where poor battery performance, the wrong battery brand in particular, can lead to a set of circumstances where the voltage can drop so precipetously that the battery hand off mechanism is dissabled and the computer can shut off before it has a chance to switch over to B2. I was convinced that the level of isolation in the vision was adequate, now i'm convinced that total isolation in a back up po2 computer is very valuable regardless of the brand of eCCR.

I use the correct batteries, swap out regularly, but none the less the above example of total system failure despite redundancy suggests to me that redundancy by a totally isolated system has it's merrits. while the chances i'll ever be left to rely entirely on the one cell back up are next to 0%, my goal is to reach 0% chance of fatal failure in practice and design.

I don't see another rebreather electronics out there that I like as much as the Vision, i'm thinking this modification, vigilance and training not withstanding, puts the finishing touches on an already very elegent system.

quickean · 13th February 2007, 22:10

The Shearwater you can indeed either do one or three cell monitoring - it recognizes how many cells it's connected to and functions appropriately.
The Shearwater also has a battery life of 500 hours.
Watch the Bruce Partridge video in the gallery video archive for DEMA.
The of the best things you can do is read the manual for each computer you are thinking about getting. Shearwater Research Inc. - Computers for Diving has a link for the Shearwater manual.
I'm not sure if the VR3 has an online manual or not as opposed to just browsing the website VR3 and VR2 Dive computer from Delta P Technology for information under features and accessories.

**Gill Envy** · 13th February 2007, 22:56

Quote: (Originally Posted by quickean)

The Shearwater you can indeed either do one or three cell monitoring - it recognizes how many cells it's connected to and functions appropriately.
The Shearwater also has a battery life of 500 hours.
Watch the Bruce Partridge video in the gallery video archive for DEMA.
The of the best things you can do is read the manual for each computer you are thinking about getting. Shearwater Research Inc. - Computers for Diving has a link for the Shearwater manual.
I'm not sure if the VR3 has an online manual or not as opposed to just browsing the website VR3 and VR2 Dive computer from Delta P Technology for information under features and accessories.

quickkean and divetheworld, thanks for the feed back. Taking a good look through the manuals is a must and I will do.

If anyone else had good or bad or better things to say about either due to real world experience I'd sure appreciate hearing about it, reading flowery manuals has it's value and limits.

A call into Bruce is certainly in order as well.

Ben Field · 14th February 2007, 09:18

I got a shearwater last year, very happy with it, does exactly what was promised.

Was impressed by the "no need to have read the manual to operate" simplicity of the software, to me this is a stand out feature.

To be honest I never owned a VR3, the experience I witnessed others having put me off but alot of people like them and the new Universal sensors/HUD package looks interesting, but probbaly OTT for adding to a Vision.

If you forced me to say something bad about the GF all I can think of is- its larger than a VR3 and when I first got mine it had a fischer connector, something I believe has no place being on or near a diver because its so fragile- fortunately Bruce makes a hardwired version so I'm getting mine "upgraded".

BEN

**PhilSiswick** · 14th February 2007, 09:38

If you want a reasonably priced, completely independent (i.e not sharing cells with the Vision electronics) PO2 monitoring only, you should have a look at the rEvoDream. A lot of people are using them on Inspos with 4/5 cell adaptors. A good plus is that they come with a HUD, so you can ignore them until the HUD flashes something up, or you want to cross-check to the Vision displays.

I haven't done it yet, as a BOV came my way and I've spent the money on that for now, but I'm going to fit one of those to my Vision later in the year.

Cheers,

JonnyB · 14th February 2007, 12:35

[quote=divetheworld;96154]The Shearwater connects in parallel with your existing three to give on-line PO2 and (GF)deco.
[quote]

sorry for the hijack guys...
this is something i have been thinking about doing with my meg, anyone knows if it is possible?

/Jonny

13th February 2007, 19:58	#1 (permalink)
Gill Envy Shearwater Copis Divers Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,347	Sheerwater vs VR3 for an EVO 4th cell? I've been won over to the concept that a totally independent 4th cell driven po2 and deco computer would be the single most valuable modification to our Evolutions, and pretty much any eCCR. I want to hear from users of VR3's and Sheerwater's about their reasons for recommending one or the other for this application. Any details on build quality issues, deco algorithms match with the Vision and any other incedentals would be great. The warrenty is soon to run out on our evo's, and after a year of diving them as designed, i'm getting ready to make a change or two, your insights would be most appreciated. __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°>
(Offline)

13th February 2007, 20:19	#2 (permalink)
divetheworld Dive porn pimp Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Inspiration Vision Classic Kiss Other CCR Join Date: Mar 2005 Location: Leeds, England Posts: 1,636	Re: Sheerwater vs VR3 for an EVO 4th cell? The Shearwater connects in parallel with your existing three to give on-line PO2 and (GF)deco. Advantages; no need for an extra cell Runs on Gradient Factors like you Vision. Gives mV display of cells at anytime User configurable Auto setpoint switching (up/down/both) No pin numbers to release He mixes And here is the big one - 5 closed circuit and 5 seperate open circuit gas lists. When you bail out (4 push buttons) it changes gas lists and therefore look ahead deco without fuss. __________________ Attitude and self praise is no reccomendation. Dont try to be a great man, just be a man and let history be the judge of you. *WWW.NARKEDAT90.CO.UK* *http://www.grpservices.com/pursuit/* Supporting Shearwater Research Products in Europe
(Offline)

13th February 2007, 21:03	#3 (permalink)
Gill Envy Shearwater Copis Divers Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,347	Re: Sheerwater vs VR3 for an EVO 4th cell? Ok, the claim has been made that anything short of a totally endependent cell could be vulnerable to upstream voltage irregularities from the primary...due to water ingress, battery bounce or any other of the long list of remote, but possible failures a primary on any rebreather might have. I don't know of any examples to point to where this happened but in theory it has some merrit. Your thoughts? It's my understanding that the sheerwater better matches the vision for deco through a similar gradient factor and a more continuious decompression calculation...whereas the VR3 requires exact deco stops or you don't get credit. corrections? Quote: (Originally Posted by divetheworld) The Shearwater connects in parallel with your existing three to give on-line PO2 and (GF)deco. Advantages; no need for an extra cell Runs on Gradient Factors like you Vision. Gives mV display of cells at anytime User configurable Auto setpoint switching (up/down/both) No pin numbers to release He mixes And here is the big one - 5 closed circuit and 5 seperate open circuit gas lists. When you bail out (4 push buttons) it changes gas lists and therefore look ahead deco without fuss. __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°>
(Offline)

13th February 2007, 21:11	#4 (permalink)
divetheworld Dive porn pimp Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Inspiration Vision Classic Kiss Other CCR Join Date: Mar 2005 Location: Leeds, England Posts: 1,636	Re: Sheerwater vs VR3 for an EVO 4th cell? Quote: (Originally Posted by Gill Envy) Ok, the claim has been made that anything short of a totally endependent cell could be vulnerable to upstream voltage irregularities from the primary...due to water ingress, battery bounce or any other of the long list of remote, but possible failures a primary on any rebreather might have. I don't know of any examples to point to where this happened but in theory it has some merrit. Your thoughts? It's my understanding that the sheerwater better matches the vision for deco through a similar gradient factor and a more continuious decompression calculation...whereas the VR3 requires exact deco stops or you don't get credit. corrections? From what I remember, and I'm sure Bruce will correct any errors, the Shearwater doesnt use only one cell for its calculations. If one cell is out of expected range, then it is removed from the decision making process and that cell PO2 display is flashing to indicate the irregularity. It must have two similar to compare, if it does not then it defaults to 0.0 PO2 and gives a low PO2 alarm. Better than a fourth cell? I think so. There are limits to all systems of this type but once you follow one philosophy, you have to make it work in all forseeable circumstances. For a 3 cell GF computer, I think this is acheived when you include the HUD in the package. If your backing up a vision, there are limits to the amount of redundancy required and I think that any more than this is paranoia! __________________ Attitude and self praise is no reccomendation. Dont try to be a great man, just be a man and let history be the judge of you. *WWW.NARKEDAT90.CO.UK* *http://www.grpservices.com/pursuit/* Supporting Shearwater Research Products in Europe Last edited by divetheworld : 13th February 2007 at 21:17.
(Offline)

13th February 2007, 21:51	#5 (permalink)
Gill Envy Shearwater Copis Divers Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,347	Re: Sheerwater vs VR3 for an EVO 4th cell? Quote: (Originally Posted by divetheworld) From what I remember, and I'm sure Bruce will correct any errors, the Shearwater doesnt use only one cell for its calculations. If one cell is out of expected range, then it is removed from the decision making process and that cell PO2 display is flashing to indicate the irregularity. It must have two similar to compare, if it does not then it defaults to 0.0 PO2 and gives a low PO2 alarm. If I understand it correctly the Sheerwater has no audible alarms but can be fitted with an HUD. If I understand correctly, it is also capable of running off one cell like a VR3. Quote: (Originally Posted by divetheworld) Better than a fourth cell? I think so. There are limits to all systems of this type but once you follow one philosophy, you have to make it work in all forseeable circumstances. For a 3 cell GF computer, I think this is acheived when you include the HUD in the package. If your backing up a vision, there are limits to the amount of redundancy required and I think that any more than this is paranoia! while the vision has quite a bit of redundancy, I have tracked two known vulnerabilities that make me feel that a totaly isolated po2 system is justifieable (though it seems justifiable on any rebreather): 1. it has one screen, if that one screen malfunctions, you have much of your info in that one basket...the HUD does help, but requires back up deco. My thinking is, if i'm going to get a back up po2 computer i might as well get one that also has deco. 2. while the electronics have redundancy, they have a common failure point. there is more than one case where poor battery performance, the wrong battery brand in particular, can lead to a set of circumstances where the voltage can drop so precipetously that the battery hand off mechanism is dissabled and the computer can shut off before it has a chance to switch over to B2. I was convinced that the level of isolation in the vision was adequate, now i'm convinced that total isolation in a back up po2 computer is very valuable regardless of the brand of eCCR. I use the correct batteries, swap out regularly, but none the less the above example of total system failure despite redundancy suggests to me that redundancy by a totally isolated system has it's merrits. while the chances i'll ever be left to rely entirely on the one cell back up are next to 0%, my goal is to reach 0% chance of fatal failure in practice and design. I don't see another rebreather electronics out there that I like as much as the Vision, i'm thinking this modification, vigilance and training not withstanding, puts the finishing touches on an already very elegent system. __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°> Last edited by Gill Envy : 13th February 2007 at 21:55.
(Offline)

13th February 2007, 22:10	#6 (permalink)
quickean RBW Member Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Mar 2006 Location: Michigan Posts: 140	Re: Sheerwater vs VR3 for an EVO 4th cell? The Shearwater you can indeed either do one or three cell monitoring - it recognizes how many cells it's connected to and functions appropriately. The Shearwater also has a battery life of 500 hours. Watch the Bruce Partridge video in the gallery video archive for DEMA. The of the best things you can do is read the manual for each computer you are thinking about getting. Shearwater Research Inc. - Computers for Diving has a link for the Shearwater manual. I'm not sure if the VR3 has an online manual or not as opposed to just browsing the website VR3 and VR2 Dive computer from Delta P Technology for information under features and accessories. Last edited by quickean : 13th February 2007 at 22:15.
(Offline)

13th February 2007, 22:56	#7 (permalink)
Gill Envy Shearwater Copis Divers Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,347	Re: Sheerwater vs VR3 for an EVO 4th cell? Quote: (Originally Posted by quickean) The Shearwater you can indeed either do one or three cell monitoring - it recognizes how many cells it's connected to and functions appropriately. The Shearwater also has a battery life of 500 hours. Watch the Bruce Partridge video in the gallery video archive for DEMA. The of the best things you can do is read the manual for each computer you are thinking about getting. Shearwater Research Inc. - Computers for Diving has a link for the Shearwater manual. I'm not sure if the VR3 has an online manual or not as opposed to just browsing the website VR3 and VR2 Dive computer from Delta P Technology for information under features and accessories. quickkean and divetheworld, thanks for the feed back. Taking a good look through the manuals is a must and I will do. If anyone else had good or bad or better things to say about either due to real world experience I'd sure appreciate hearing about it, reading flowery manuals has it's value and limits. A call into Bruce is certainly in order as well. __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°>
(Offline)

14th February 2007, 09:18	#8 (permalink)
Ben Field CK+Shearwater Current Rebreather/s: Classic Kiss Other Rebreather/s: Sport Kiss Join Date: Aug 2005 Location: London, England Posts: 1,774	Re: Sheerwater vs VR3 for an EVO 4th cell? I got a shearwater last year, very happy with it, does exactly what was promised. Was impressed by the "no need to have read the manual to operate" simplicity of the software, to me this is a stand out feature. To be honest I never owned a VR3, the experience I witnessed others having put me off but alot of people like them and the new Universal sensors/HUD package looks interesting, but probbaly OTT for adding to a Vision. If you forced me to say something bad about the GF all I can think of is- its larger than a VR3 and when I first got mine it had a fischer connector, something I believe has no place being on or near a diver because its so fragile- fortunately Bruce makes a hardwired version so I'm getting mine "upgraded". BEN __________________ Know your PPO2, Pre-breath, Use checklists, Validate cells at 6mtrs, Use pure O2 at or near surface, Use a BOV, Don't dive Solo, Change Slime and Cells as recommended by Manufacturer and RTFM! Beware Fridge Suck! www.hugsac.org.uk
(Online)

14th February 2007, 09:38	#9 (permalink)
PhilSiswick Phil Siswick, Tango Current Rebreather/s: Evolution Other Rebreather/s: Inspiration Vision Join Date: Apr 2006 Location: Oxford, UK Posts: 1,092	Re: Sheerwater vs VR3 for an EVO 4th cell? If you want a reasonably priced, completely independent (i.e not sharing cells with the Vision electronics) PO2 monitoring only, you should have a look at the rEvoDream. A lot of people are using them on Inspos with 4/5 cell adaptors. A good plus is that they come with a HUD, so you can ignore them until the HUD flashes something up, or you want to cross-check to the Vision displays. I haven't done it yet, as a BOV came my way and I've spent the money on that for now, but I'm going to fit one of those to my Vision later in the year. Cheers, __________________ Phil (WSKD 0001) I have always felt that the dive I am on is not nearly important as the dives I plan to be on the rest of my life. Tom Rose, 2007 The person who gets the farthest is generally the one who is willing to do and dare. The sure thing boat never gets far from shore. Charles A. Lindbergh www.hugsac.org.uk
(Online)

14th February 2007, 12:35	#10 (permalink)
JonnyB Johnny The Hatch Current Rebreather/s: MK 15.X Titan Other CCR Other SCR Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Megalodon Sport Kiss Classic Kiss Other CCR Other SCR Home Build Join Date: Jan 2005 Location: Sweden (Stockholm)/Cyprus(Ayia Napa) Posts: 991	Re: Sheerwater vs VR3 for an EVO 4th cell? [quote=divetheworld;96154]The Shearwater connects in parallel with your existing three to give on-line PO2 and (GF)deco. [quote] sorry for the hijack guys... this is something i have been thinking about doing with my meg, anyone knows if it is possible? /Jonny __________________ A quote from Crazyduck - In remembering our own Rob Davies. "Outbound flight 777 heavy you are cleared for flight Due west into that warm red Texas sunset You have angels on your wings and divers memories on your six." Rest In Peace http://www.divetekcyprus.com http://www.diveccr.com
(Online)

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