Whats Wrong with VPM-B

[hobodiver]

Funnily enough both those factors are monitored and used to adjust the deco obligation by the UEMIS as far as I know.

How does it monitor body temperature? Or do I not want to know that?

 

[BB1]

Bit of an oops on my part but only slightly different to what I remembered.

Quote from UEMIS as discussed here in a "Why ZH-L8+ not VPM":
"Skin temperature is estimated according to water temperature and time. Workload is measured
by monitoring the respiration. Microbubble formation is mainly based on the
pressure/time profile and physical and physiological data. With the logging
features of these dive computers, the model could be verified."

This is taken from the FAQ on their website:

"ZH-L8+. Adaptive Buhlmann modell with real time consideration for micro bubbles, workload of the diver, skin cooling and (mandatory) deep stops. The safety margin of the model can be adjusted to your needs."

 

[Kern]

Sounds like a bunch of marketing, but then, that does sound better than real time probes. How does it know if I'm diving a wet or dry, etc. etc.?

How does a single phase model have real time considerations of the gas phase?

 

[Liquivision]

In this case, to me it feels more like a burden. I don't want to complete a PhD in decompression theory, I just want to dive safely, according to what the latest science says. Just as I don't feel like completing an MD before getting a treatment for an illness, I'd rather rely on an expert who has studied the data to tell me what I, as an "end-user" of all this theory, should go by.

Is there such a thing?

Yes, basic question, I know. I'm just getting into technical diving. So far I've completed only a handful of technical dives. It's hard to do in Southern Arizona. But I'm hoping to get to do it more frequently.

In my deco class, I learned that V-Planner was the software to go by. Is that no longer advisable?

Yes, as RJack says... there are plenty of self-proclaimed "experts," especially among technical instructors (of which not all are made equally)... just ask them! Then, there are actually several people just in this thread who's knowledge of decompression theory I greatly respect.

Similar to what brands of dive gear they wear, you'll find most people will endorse (whether with information or ignorance) the algorithm they use and/or were trained on as "the best." The fact of the matter is that decompression is more of an art than a science, and no two canvases (i.e. divers) are exactly the same. V-Planner works for a lot of people, as does a ZHL-16GF, as does Ratio Deco, etc. Finding what works for you comes from experience and hopefully diverse instruction. There are plenty of ways to skin this cat... find the way that works best for you.

BTW - Regarding Tucson... I'm Salpointe Alumni.

-Doug
Liquivision Marketing & Sales Manager

 

[Nailer99]

Am I the only one who thinks the whole algorithm debate is silly? I've been using Ross's excellent vplanner to cut tables for tech dives since I started deco diving. It uses VPM. I use +2 conservatism on it. I've also been using Bruce's excellent Shearwater computers for years- I've owned one of every model, from GF to Pursuit to Predator. They currently use Buhlman with Gradient factors- I have mine set at 15/85. Now, I don't log my dives in any way that would make it easy to count them up, but I'm quite sure that I have way more than 100 deco dives under my belt, and the majority of them are between 200-300 fsw in cold, murky water, and I've never had so much as a rash or a twinge of DCS.

Here's the interesting part: I have never seen more than a 2 minute discrepancy between my computer and my dive tables. Every stop is identical, all the way up to the shallows- and that one time I saw 2 minutes, it was at my 10' stop- I cleared my tables 2 minutes before my computer on a two hour long deco. I don't know about any of you, but I don't consider 2 minutes to be a big deal when it comes to deco.

WHY is everyone so worked up over this, anyway? I'm genuinely curious, and I've never heard an answer that made any sense to me. I really don't give a damn about the minutia of deco theory- I think it's incredibly boring, especially in light of the fact that I am already doing something that seems to work just fine for me.

 

[TSandM]

Josh, the dives you do are PERFECT for tables -- you're a wreck guy, doing very square and very predictable profiles. If you're doing terrain-based deco diving, or caves, profiles may not fit into tables very well at all, and the fudging one has to do to make them fit may definitely lead to some discrepancies with a real-time algorithm.

That said, a couple of minutes difference here and there, or overall, probably isn't the determining factor in whether one has symptoms.

 

[Kern]

Nailer, I don't think I'm terribly worked up over the issue of who uses what algo on a dive. You're not interested in deco theory, I am, each to their own is all I can say. I am interested in what other people do & why though.

I do have a question for you. If 15/85 GF didn't approximate the same curve as you get from VPM +2, would you change your GF's so they did, or would you dump VPM for static planning.

 

[Kern]

Josh, the dives you do are PERFECT for tables -- you're a wreck guy, doing very square and very predictable profiles. If you're doing terrain-based deco diving, or caves, profiles may not fit into tables very well at all, and the fudging one has to do to make them fit may definitely lead to some discrepancies with a real-time algorithm.

That said, a couple of minutes difference here and there, or overall, probably isn't the determining factor in whether one has symptoms.

My real time runs on a wreck using a VPM based computer, are often quite different to my static VPM based plan. Most wrecks I dive, aren't a debris field scattered on a flat bottom.

 

[Nailer99]

OK, but.....would different profiles yield vastly different results? I have done this tables/ computer matching plenty of times at places like cove 2, which is a long gradual slope. Only thing I haven't done is a sawtooth profile this way, really. And they always synch up.

Josh, the dives you do are PERFECT for tables -- you're a wreck guy, doing very square and very predictable profiles. If you're doing terrain-based deco diving, or caves, profiles may not fit into tables very well at all, and the fudging one has to do to make them fit may definitely lead to some discrepancies with a real-time algorithm.

That said, a couple of minutes difference here and there, or overall, probably isn't the determining factor in whether one has symptoms.

 

[Nailer99]

Good question. I never thought about it before. I just started diving this way because it's how I was taught- my instructor used vplanner and a shearwater. I remember watching my computer generated stops line up with my tables on my first trimix dive and marvelling at this phenomenon...

Nailer, I don't think I'm terribly worked up over the issue of who uses what algo on a dive. You're not interested in deco theory, I am, each to their own is all I can say. I am interested in what other people do & why though.

I do have a question for you. If 15/85 GF didn't approximate the same curve as you get from VPM +2, would you change your GF's so they did, or would you dump VPM for static planning.