analog vs digital gauge (SPG vs Air Integrated Dive Computer)

[snsb]

Hi

After reading many forums it shocked me that there are more than one case where SPG failure occurred.

So I wondered if air integrated dive computer/console would be a better option in reliability and accuracy (when full/low on gas)?

Also, can modern SPG (digital and analog) handles the tank pressure when turned on instantaneously, or do we still need to ease pressure by purging the regulator?

 

[NAM001]

Can it handle it. I say yes the hose has a very small hole to bleed air into the line to the spg. I have had more problems with pressure sensors in air integrated units whether they be hose or hoseless. I prefer the mechanical spg. a replacement gage is cheaper than repair of the pressure sensor in integrated units. 5 years using the spg and it is still reading correctly. I check it regularly.

 

[Steve_C]

Hi
Also, can modern SPG (digital and analog) handles the tank pressure when turned on instantaneously, or do we still need to ease pressure by purging the regulator?

I am curious. What does purging the regulator have to do with it? You crack on the air and the SPG registers the full pressure almost immediately. Best to get in the habit of only having you tank full off or full on. Diving with a tank partially on is no joy at depth. When you see folks purging regulator I think they are testing the reg. But the best way to do that is to breath on the regulator and while you do that watch the SPG. If the needle moves noticably then your air is not fully on like it should be and you turn it on full. The last thing I do begfore stepping on the water is to breath on my reg while looking at my SPG. Saved my tail in cancun.

 

[AJ]

Some regs can't handle full pressure directly when turned on. That's why some people purge the reg while opening the valve. It has nothing to do with the SPG as far as I know off.

 

[keyshunter]

Steve,
I think that the idea of holding the purge open when pressurizing the reg comes not from the spg, but from the reg's first stage. And, of course, someone decided if it is good for one it is good for the other. Anyway, the old idea is that since the first stage seat is open when not pressurized, holding the purge would reduce the slamming effect of suddenly turning on the air and thus save pounding on the soft seat. In actual practice, I doubt that it makes much difference, but it certainly doe not hurt to pressurize slowly.

 

[Colliam7]

So I wondered if air integrated dive computer/console would be a better option in reliability and accuracy (when full/low on gas)?

I don't think there are any data to support the idea that air integration (hose connection to the computer) is more reliable. But, I don't think there are data to suggest it is less reliable either. From personal experience, wireless air integration is slightly less reliable. As kws said, there may be a difference in cost of addressing the failure of the pressure sensor vs the SPG. Use of one or the other is primarily a matter of personal preference (I prefer a simply SPG (only) on a HP hose, with my computer on my wrist). Others have different preferences.

Also, can modern SPG (digital and analog) handles the tank pressure when turned on instantaneously, or do we still need to ease pressure by purging the regulator?

Yes, they can. The practice of placing your finger on the second stage purge button when initially opening the valve, and slowly releasing it after the valve is opened, is related more to not 'slamming' the first stage with a higher pressure. Honestly, I am not sure that is even necessary these days, but it is a common instructional practice. I have seen one instance, where there was apparently a slight leak in a bourdon tube, and the plastic face cover of a SPG popped off (and flew across a 10 foot space) when the system was pressurized without a purge button being depressed. That shouldn't happen (the case space should not build pressure in the event of a leak), but it did in that instance, and probably would have happened even if the purge button had been depressed, and slowly released.

 

[cashew]

So I wondered if air integrated dive computer/console would be a better option in reliability and accuracy (when full/low on gas)?

I personally dive with both - a wireless AI as my primary, with a secondary analog SPG as a backup. Can't hurt, right?

I'm about 30 dives in on diving both and I haven't noticed any wild variation between the two as to reading tank pressure.

 

[Jim Lapenta]

Besides the fact that I don't want an ai computer there is the issue of me having 9 reg sets that I could be using at any time. Moving around a transmitter would be highly impractical.

 

[tbone1004]

I'd be OK if they came out with a very simple digital SPG that was the profile of the normal SPG's and didn't cost significantly more. Unfortunately that hasn't happened yet and none of the wired AI computers are worth purchasing. Such is life. Seabear did well by incorporated a digitial pressure sensor in their HUDC which is a super nice feature that I wish Shearwater would add to their NERD to make it better for PSD and scientific diving, but can't have everything.

The digital gauges are definitely more accurate at the extremes of the ranges than analog gauges, which is part of the reason not to let your tank run too low, but again, it's not worth the tradeoffs of the current AI computers on the market.

 

[snsb]

Hi

Thanks everyone for the tips and experiences.

I guess I will go with digital as I have never read a case of digital failure before.

(I read like 5 cases of SPG needle being stuck and the case that, 'Colliam7' mentioned about, the cover popping off twice)

Hopefully modern digital gauge is somewhat less prone to malfunction : )

Ps, Is there any highly regarded digital console that I should look into? (Currently, I like the idea of Proplus3 but its hard to find a review online)