Is an SPG necessary with a wireless computer?

[John_B]

Great zombie thread!

If you had a GPS in the wildenress, would you do without a paper map?

As something of a backpacker myself I really enjoy using my Garmin Dakota, but there is no way in hell I'd ever head into the backcountry without good old-fashioned waterproof maps and a compass as a backup.

Then again, back when I tried an AI computer my SPG was rock-solid reliable when the Suunto transmitter would get finicky. If I were to ever go back to an AI dive computer, I'd still run a brass and glass SPG on the left. Maybe with the transmitter on a short HP hose as I've seen transmitters broken right at the threads of the HP port due to rough handling (usually from being used as an extra handle).

 

[Searcaigh]

My Garmin GPS60 failed on me on Saturday (second time this year) when I really needed it most to locate a specific dive site. It was too hazy to use land based points to put us directly over the site. Found the site on the second dive. I have re-uploaded the software again and is now working once more.

Back to dive instruments, I use SPGs on all of my reg set ups, no batteries to fail or suffer from interference from any other sources.

When I was diving at Puerto Galera two years ago one of the divers in my group had issues when the strobes on his camera fired, his computer lost the pressure reading! He ended up renting and fitting an SPG.

 

[ijdod]

I've always had both the SPG and a transmitter, but when I started using one of the DS4s of my twinset for my holiday dives, which has just a single HP port, I've decided to drop the SPG. I still carry it with me, as spare. As far as failure rates are concerned, I've had 2 SPG o-ring failures so far, and have witnessed quite a few others, but I have yet to see a transmitter fail. I realise this is just my N=1 observation, but either failure typically should end the dive anyway.

 

[charlesml3]

If the transmitter fails you either...

-Call the dive and ascend:
-Continue the dive with a back-up SPG:

Or:

- Be knowledgeable of your own air consumption and make an informed decision. Pay attention. Is the tank starting to feel light? An experienced diver should know when they've been down for an hour and know "it's about time to head up." Move closer to your buddy in case you're off a bit. A clear, shallow, warm-water dive.... there's no reason to just bail because the gauge failed. It's not like you have absolutely no idea how much air is in the tank just because you can't read the gauge.

---------- Post Merged at 12:30 PM ---------- Previous Post was at 12:30 PM ----------

I dive with 3 second stages.
See if you can figure out where I come down on this one.

Paranoid? That's what I'm going with. Do you also wear a belt AND suspenders just in case one fails?

---------- Post Merged at 12:38 PM ---------- Previous Post was at 12:30 PM ----------

Even when ( if?) I go to a transmitter, I would like a fail safe way to track my gas U/W.

Then you need to keep looking. A SPG is not "fail safe." I've been diving now close to 30 years and seen 2 SPGs fail. Both got "stuck" and were reading something greater than 0 with the entire reg detached from a tank.

used to say the SPG wasn't really necessary, until the day I changed the batteries in my computer and transmitter, and the transmitter went dead.

I didn't know it until we were on a dive boat gearing up to get in the water...no signal.

Well OK but this was a failure on your part, not the computer/transmitter. You know as well as anybody that batteries have a shelf-life. You should have tested the setup before you left the dock instead of waiting until just before you jumped in.

 

[aquaregia]

Off topic, but do you know why Uwatec recommends the left HP port for your transmitter? I would have assumed all HP ports were created equal.

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

 

[j2s]

You can put a 'button' [Pony] gauge on a hose [whatever length works best] and route it however it's convenient for you; along the inflator, the octo, [attached w/velcro, inner tube or bungee] under your arm etc.....What ever is most streamlined and accessible......I've seen them routed under the arm, then attached to a 'D' ring [w/a tie-wrap] on the shoulder strap so you can look down and see the pressure w/just a quick glance....Pretty much 'hands-free'.......

 

[eelnoraa]

If you had a GPS in the wildenress, would you do without a paper map?

Not apple to apple analogy. If the GPS dies, I will still have my iPhone. If the iPhone dies again, there will be more smart phones in the group. Chance of all the GPS capable devices die together is very low. A group of hikers can share one GPS. A group of divers can't share one SPG.

Anyway, the key here is redundancy. If I have multiple AI computers/tranmisstters, I will say SPG is not needed either.

 

[DevonDiver]

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

 

[eelnoraa]

I think it is not the acutal reliability of the unit, but rather the battery. My experience went like this. I was assigned to station in Shanghai for a few monthes. Before I left home, I knew I will be diving, so I replaced batteries on both wrist unit and transmitter. Stayed in Shanghai for two monthes, then went on a live aboard in Thailand. So they are two month old NEW batteries. First day of diving, both battery indicator showed full bars. First dive on 2nd day, couldn't sync up anymore. I have SPG, so I kept diving for the rest of the trip. Afterward, I figured out battery in transmitter was dead.

Another more scary problem is crew in live aboard treat the transmitter as handle all the time. I caught it once, and told them not to, but who know when I wasn't looking. The chance of it breaking off is real.

 

[aquaregia]

Not apple to apple analogy. If the GPS dies, I will still have my iPhone.

Of course not! That's an Apple to Garmin analogy.

(sorry)