Is an SPG necessary with a wireless computer?

[Mantra]

I really like the convenience of having the computer on my wrist. The transmitter is on the left hand side, as I wear the computer on my left wrist, and the signal seems more reliable if the transmitter is on the same side as the computer. This is a slightly older computer, though (atom 2.0). For that reason I have the SPG clipped off on my right hip. I'm not very DIR though and dive a jacket BCD. I like having the redundancy, and also like to have the analog gauge for a pre-dive check so I can watch the needle when breathing the reg to see if it is wobbly, indicating that the tank might not be fully open.

 

[charlesml3]

Is there really an issue with transmitter reliability nowadays.... or is this a legacy belief from earlier generations of technology?

Yea, I think that's what it is, really. Then there's the DIR crowd with "We don't need no stinkin' 'puters." And the crowd that equates a dive computer with the PC sitting on their desk although they're wildly different.

-Charles

 

[markmantei]

I assume it's so you don't accidentally loosen your transmitter instead of turning on your tank valve.

What to do then with left handed valves

 

[AfterDark]

I work high tech I see the problems and "glitches" 40 hours a week. I would never not even on a bet trust something as important as my gas supply to anything with cpu(s) or any kind of HT electroincs. No way! I'd rather go back to using a J valve! I still use my 40 year old SP SPG. It has never failed. I'm closing in on 2000 dives mostly in the cold rough waters of New England, diving all year round. It's in the same console. It's been beat on rocks in heavy surf more times than I can remember. Banged against boats, ladders, even my cellar floor. Still ticking. Let me know how yours holds up.

 

[flots am]

Is there really an issue with transmitter reliability nowadays.... or is this a legacy belief from earlier generations of technology?

Some wireless computers have issues with nearby electronics like strobes. The solution is to use appropriate technology. The people who have this problem know it, and would be much better off replacing the computer than bring along a rabbit's foot. Sometimes computers just fail. Sometimes SPGs just fail. Sometimes regulators fail. That's what training is for.

On a no-deco dive, a failed computer means "go up", just the same as a failed SPG means "go up". A redundant SPG does not allow the diver to continue the dive because there's no way to map nitrogen loading or no-deco time between tables and computer unless it was a square, known profile.

The only useful information a spare SPG conveys is "How much air do I have left?" which is something the diver should have been monitoring all along, before the failure.

flots.

 

[James R]

Seems like we have this same thread every few weeks.

I don't take a spg on recreational single tank dives. Ever. Why not? It's because I monitor my gas frequently enough that I would know very soon after I lost my transmitter/computer connection. It would not be a panic situation in any way. I would simply turn the dive and get out of the water. I do take a spg on a 24" hose with me on trips, but I have yet to use it myself. I have loaned it to someone who had another spg fail (I don't recall why or what happened to his).

I definitely take spg on every technical dive or any recreational dive with doubles. The spg is on the left post 1st stage and I never remove it. I also put my transmitter on my right post 1st stage, pointed down, which helps keep it clear of dangers/impacts. I do check my spg a couple times during the dive, and compare it to my AI computer to make sure they are showing the same pressure (eg ensure manifold isolator is open). In the unlikely event I have to shut down a valve to resolve a problem I still have a way to monitor the gas supply in the cylinder I am breathing from.

FWIW my AI computer (Uwatec Luna) has 537hrs logged with no failures save a torn strap which I have replaced with bungee cord (and like a lot better than the oem strap!!).

 

[John_B]

Yea, I think that's what it is, really. Then there's the DIR crowd with "We don't need no stinkin' 'puters."

Congratulations, you've mastered the slippery slope argument.

And the crowd that equates a dive computer with the PC sitting on their desk although they're wildly different.

In IT I see computers of all types fail every day. The ones that sit on your desk, the big ones that sit in server rooms or data centers, and the embedded variety that sit inside a device not terribly different from a dive computer. Something that requires pressure seals and uninterrupted underwater radio signals is hardly immune.

On a no-deco dive, a failed computer means "go up",

Yes. Unless you have a backup.

just the same as a failed SPG means "go up". A redundant SPG does not allow the diver to continue the dive because there's no way to map nitrogen loading or no-deco time between tables and computer unless it was a square, known profile.

No. Your dive computer continues to track depth, time, nitrogen loading, remaining NDL, etc. even without the air integration information (i.e. tank pressure). What you do lose is tank pressure and -- at least with the Suuntos -- estimates for your remaining air time. And, yes, you should be able to calculate a pretty good WAG of that with just your brain. (DIR or no.)

The only useful information a spare SPG conveys is "How much air do I have left?" which is something the diver should have been monitoring all along, before the failure.

Yes.

 

[AfterDark]

Some wireless computers have issues with nearby electronics like strobes. The solution is to use appropriate technology. The people who have this problem know it, and would be much better off replacing the computer than bring along a rabbit's foot. Sometimes computers just fail. Sometimes SPGs just fail. Sometimes regulators fail. That's what training is for.

On a no-deco dive, a failed computer means "go up", just the same as a failed SPG means "go up". A redundant SPG does not allow the diver to continue the dive because there's no way to map nitrogen loading or no-deco time between tables and computer unless it was a square, known profile.

The only useful information a spare SPG conveys is "How much air do I have left?" which is something the diver should have been monitoring all along, before the failure.

flots.

A backup SPG would allow this diver to continue his dive. This diver takes redundant depth gages, timer and watch, as well as a PDC (that functions more as a depth gauge for me I got it to make the charters boat cpt. smile) and if diving deco his stops are on both his slates. I only have one spg per reg. I dive ID's which means I have another tank, reg and spg. If it's a no deco dive you bet I'm diving even if I have to change my plan on the fly. One of the many advantages of solo diving and years of experience.

 

[flots am]

A backup SPG would allow this diver to continue his dive. This diver takes redundant depth gages, timer and watch, as well as a PDC (that functions more as a depth gauge for me I got it to make the charters boat cpt. smile) and if diving deco his stops are on both his slates. I only have one spg per reg.

I'm always willing to learn something new.

I did a couple of dives in the morning, now it's 3PM. My bottom timer says I've been in the water for 50 minutes and I have 1500PSI left.

What's my remaining no-deco time?

flots.

 

[AfterDark]

I'm always willing to learn something new.

I did a couple of dives in the morning, now it's 3PM. My bottom timer says I've been in the water for 50 minutes and I have 1500PSI left.

What's my remaining no-deco time?

flots.

That's for you to answer, no one else.