SPG or Not? (Dive computer w/ air int)

[davecampbell]

when diving doubles (100% of my local diving) I run the transmitter on the right post, and an spg on the left. It stays clipped off during the whole dive, except for pre-dive pressure checks, or transmitter connection issues, which are fairly rare. For singles during travel, I run both.... likeliest failure is transmitter battery or connection issues, and an spg means I continue the dive, old school.
I service my own gear, regularly and carefully. I inspect it often.... I don't worry about the extra "failure" points.

 

[rx7diver]

... The gauge I saw from the same manufactor is 20% of the cost of the computer.

... Thoughts? Thanks in advance.

@wordizbon,

I still dive the Scubapro (B&G) SPG I purchased new in 1987. It still seems to be holding its calibration. And it never needs batteries, nor has it ever had a syncing issue. (I don't dive a PDC.)

FWIW,
rx7diver

 

[34109411]

i am in love with my sherwater tx anyway before that i used a mares quad air. Since this time i didn't go back to a spg.


What i like about the TX is the sidemount mode, i specifically buy it for this along with the digital compass.

 

[lizardland]

@wordizbon,

I still dive the Scubapro (B&G) SPG I purchased new in 1987. It still seems to be holding its calibration. And it never needs batteries, nor has it ever had a syncing issue. (I don't dive a PDC.)

FWIW,
rx7diver

Same. In 30 years I've never experienced any of the mythical horror stories about stuck needles or dangerously inaccurate readings. The worst I've ever had was a bubbling hose and a few spools that needed replacing.

 

[tursiops]

Same. In 30 years I've never experienced any of the mythical horror stories about stuck needles or dangerously inaccurate readings. The worst I've ever had was a bubbling hose and a few spools that needed replacing.

I lead dive trips. The most common field repair is a replacement spool on an SPG. Very occasional stuck needle or one that does not return to zero.

 

[Badger7]

This post is anecdotal and bound to offend AI purists. Please accept my apologies in advance, but I am who I am and do what I do because of the experiences that I have lived.

I've had a Garmin T2 transmitter stop sending pressure to a Mk3i in the middle of a deep quarry dive, but I had an SPG clipped to my left hip so I knew I had plenty of gas to turn the dive and head back in a lesuirely manner without needing to make an ascent and a longish surface swim. Replacing the battery and attempting to reconnect it did nothing, Garmin replaced the transmitter under warranty, and the replacement has worked perfectly fine since.

I've had a Shearwater Swift stop communicating with a Perdix 2 during a SI on a wreck diving weekend. I "deleted it" by writing over the serial number with zeros, replaced both batteries, put the serial number back into the computer multiple times, updated perdix firmware, etc. I did the final dive that day without AI since I had an SPG clipped off to my left hip, and the only issue was the swift showing no connection. Back at the hotel that night I put the same serial number I had typed in a dozen times and had dive buddies proof into the T2 slot instead of the T1 slot and it started recieving pressure again. I blanked out the T2 slot I put it back in the T1 slot and it has worked for months now ever since, and I haven't bothered Shearwater with it because its been 100% reliable over dozens and dozens of dives since.

I'm not going to leave my SPG in the truck, back at the hotel, or in my boat crate because on two occasions it has been far more useful clipped to my hip. So why don't I just skip the transmitters on my rec and tec regs entirely? I like the data, and I like seeing an accurate SAC calculation for different dive conditions. Multiple failure points? Please. If I didn't consider either AI transmitters or HP Hoses and SPGs to be relatively safe I wouldnt be using either of them and neither would you.

 

[ImpotentSeaSnake]

For rec diving, you probably don’t need redundant AI. AI plus an SPG gives you a back up to save a dive and it makes it easier to check tanks on the boat when getting kitted up. Plus if I ever became incapacitated underwater, it’s easier for a buddy or rescuer to check your air with an SPG than a computer they may not be familiar with.

 

[Centrals]

Make your own decision as there is NO right or wrong here.
I am NOT surprised that this question kept popping up now and then.

 

[Dan]

My SPG is small & thin, no battery required. It’s reliable. I had no SPG failure in 20 years, almost 2000 dives.

I have AI failures twice (dead battery & Teric AI broken antenna). With SPG as a back up, I continued my dives during those AI failures.

 

[Nicholas_D]

This post is anecdotal and bound to offend AI purists. Please accept my apologies in advance, but I am who I am and do what I do because of the experiences that I have lived.

I've had a Garmin T2 transmitter stop sending pressure to a Mk3i in the middle of a deep quarry dive, but I had an SPG clipped to my left hip so I knew I had plenty of gas to turn the dive and head back in a lesuirely manner without needing to make an ascent and a longish surface swim. Replacing the battery and attempting to reconnect it did nothing, Garmin replaced the transmitter under warranty, and the replacement has worked perfectly fine since.

I've had a Shearwater Swift stop communicating with a Perdix 2 during a SI on a wreck diving weekend. I "deleted it" by writing over the serial number with zeros, replaced both batteries, put the serial number back into the computer multiple times, updated perdix firmware, etc. I did the final dive that day without AI since I had an SPG clipped off to my left hip, and the only issue was the swift showing no connection. Back at the hotel that night I put the same serial number I had typed in a dozen times and had dive buddies proof into the T2 slot instead of the T1 slot and it started recieving pressure again. I blanked out the T2 slot I put it back in the T1 slot and it has worked for months now ever since, and I haven't bothered Shearwater with it because its been 100% reliable over dozens and dozens of dives since.

I'm not going to leave my SPG in the truck, back at the hotel, or in my boat crate because on two occasions it has been far more useful clipped to my hip. So why don't I just skip the transmitters on my rec and tec regs entirely? I like the data, and I like seeing an accurate SAC calculation for different dive conditions. Multiple failure points? Please. If I didn't consider either AI transmitters or HP Hoses and SPGs to be relatively safe I wouldnt be using either of them and neither would you.

Maybe I'll add to the offense, but this right here is spot on. I love having the extra info and convenience of the AI, but it's not failsafe. I had my perdix AI lose coms last dive. It eventually came back, but I was happy to have my SPG in the meantime.