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Thread: Sheerwater vs VR3 for an EVO 4th cell?

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    Shearwater Copis Diver Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy's Avatar
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    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

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    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.
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    Shearwater Copis Diver Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy's Avatar
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    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  View Original Post
    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

  4. #4
    Brent - Narked at 90
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    Re: Sheerwater vs VR3 for an EVO 4th cell?

    Quote Originally Posted by Gill Envy  View Original Post
    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!
    Last edited by divetheworld; 13th February 2007 at 20:17.
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  5. #5
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    Re: Sheerwater vs VR3 for an EVO 4th cell?

    Quote Originally Posted by divetheworld  View Original Post
    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  View Original Post
    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.
    Last edited by Gill Envy; 13th February 2007 at 20:55.

    Gill Envy

  6. #6
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    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 21:15.

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    Re: Sheerwater vs VR3 for an EVO 4th cell?

    Quote Originally Posted by quickean  View Original Post
    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

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    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

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    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,

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    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

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