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SPG's are usually most accurate in the center of their range. Gauges that read more than zero when unpressurized never leave the factory, but gauges that may read "0" when they still have 100-200 psi are pretty common and not viewed as being problematic as they are more conservative.
Not all button gauges are created equally. The old ones were small and very hard to read - even on the surface. The newer ones are much larger and come in two flavors - one with about 120 degrees of needle movement and one with 180 degrees.
All that said, on a stage I prefer a very accurate conventional SPG on a 6" or 7" hose since the turn pressure matters and accuracy and discrimination count.
On a deco bottle, I'd argue you don't need one at all. You check the pressure pre-dive, ensure you have at least 1.5 times what you need for the dive and then you have what you have. You can't make more during the dive so there is no real value in having a gauge.
In that regard it can be argued that a gauge just adds failure points. On the other hand if you feel you have to have one on a deco bottle, it makes more sense to have a button gauge. It adds only a one bourdon tube in a fairly tough brass body over the o-ring and plug you have already and is much simpler than the o-ring hose, and HP swivel and bourdon tube used with the larger brass and glass gauge.
I would have to disagree. If your gauge is that inaccurate from the start how do you know if you have 1.5 times the deco gas or 1.4? one of those two numbers is going to result in some grey hair if you or your buddy loses his or her gas. Moreover, SPG's are pretty failure resistant. Enough so that I am content with their potential for failure. I do not see the need to fix something that is not broken.
The reality is that conventional gauges fail in 2 ways:
1) The faces cracks and you can still read it for quite awhile albit flooded.
2) The spindle orings poop out and you get champagne bubbles but lose only a modest amount of gas due to the HP orifice in the reg body.
Neither of these failures are nearly as bad as miscalculating the amount of deco gas you had in the first place cause you read a button gauge wrong.
Dumpster Dive, if the reasons posted above are not "good" in your view, I don't think Chris and I are going to lose any sleep over it. Neither of us are scuba cops so have fun. Not trying to be impolite but you did post in the DIR forum, so don't be surprised you got some DIR answers.
I posted it in the DIR section because I feel that the DIR stuff generally makes a lot of sense. I dive solo and do other things that are not DIR, but learning why DIR chooses certain configurations has been valuable to me in the past.
If there was some kind of history of failure or something I would be very interested. The accuracy issue is a non-issue to me.
I also find a little humor in someone saying the old standard guage has a low failure rate so it is not something to worry about and it is an acceptable configuration (exactly what I say about my AIR 2, LOL). I thought the DIR concept was to reduce potential failure points and a primary way to accomplish this was by simplicity. The button guage certainly SEEMS simpler to me.
Also, for anyone who still has good eyes, you can easily protect the old tiny button guages by heating a piece of pvc pipe up until soft, and then slipping it over the button guage so that a small lip of pipe protrudes from the end of the guage...no more scratches and the pvc rim will mitigate a lot of rough handling and/or a dropped stage (pony) regulators.
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SCUBA Diving: The only sport where grown men will brag about how low their sac is.
The reality is that conventional gauges fail in 2 ways:
1) The faces cracks and you can still read it for quite awhile albit flooded.
2) The spindle orings poop out and you get champagne bubbles but lose only a modest amount of gas due to the HP orifice in the reg body.
Neither of these failures are nearly as bad as miscalculating the amount of deco gas you had in the first place cause you read a button gauge wrong.
On a pony bottle its all irrelevant.
Even though your boat is not bulletproof, I still have to agree.....
I also find a little humor in someone saying the old standard guage has a low failure rate so it is not something to worry about and it is an acceptable configuration (exactly what I say about my AIR 2, LOL). I thought the DIR concept was to reduce potential failure points and a primary way to accomplish this was by simplicity. The button guage certainly SEEMS simpler to me.
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DIR is about reducing failure points, but it is also about reasonable assessment of risk. Don't forget DIR is a system and a reduction in failure points in one area may impose unacceptable risk in another. You have to look at the system as a whole and understand how everything works together, with the intention of reducing the overall risk to an acceptable level.
As I said, my biggest concern about the ad was that the gauge might turn out to be no bigger than the one I have, which is all but unreadable.
Having not done any technical training involving decompression gases, I really shouldn't speak about how accurate a gauge on a deco bottle is. But I have to confess that I had the same general idea as someone above, which was that what you wanted to be sure of was that the bottle was full . . . I guess I have a lot to learn yet!
So I guess accuracy and readability are the big issues with the button gauges? If we are all very polite about saying that, we might not alienate as many people . . .
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If there was some kind of history of failure or something I would be very interested. The accuracy issue is a non-issue to me.
In my personal opinion, the lack of accuracy is probably the single biggest issue. So if this is a non-issue for you, the button gauges may work for you.
Quote:
Originally Posted by dumpsterDiver
I also find a little humor in someone saying the old standard gauge has a low failure rate so it is not something to worry about and it is an acceptable configuration (exactly what I say about my AIR 2, LOL). I thought the DIR concept was to reduce potential failure points and a primary way to accomplish this was by simplicity. The button gauge certainly SEEMS simpler to me.
Bismark is absolutely right, DIR needs to be examined as a system (notice I avoided the word holistic ). As previously pointed out, accuracy is especially important with stages. We use the same regs for all our bottles and so button gauges are not a good option for us. Although I'm not entirely convinced that button gauges are less likely to fail than standard spgs on a 6" hose.
From a DIR stand point wouldn't a button gauge possible cause some annoyance when going to a deco gas when you have both a 70' and 20' Oxygen bottle?
It's nice being able to actually grab the SPG when you purge your deployed reg and validate you are on the right bottle. Seems like a button gauge might be harder to work with.
). As previously pointed out, accuracy is especially important with stages. We use the same regs for all our bottles and so button gauges are not a good option for us. Although I'm not entirely convinced that button gauges are less likely to fail than standard spgs on a 6" hose.
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