Shearwater Owners with AI, do you dive with a SPG?

[Tracy]

They will not work in a Shearwater Predator. Only SAFT will work and as I stated above - finding reliable vendors for SAFT has been elusive for me.

You can run a rechargeable 3.6v battery. That is what I used to run in my hammerheads. I think they are 14500 size.

 

[bpodbielski]

No

I use my SPG for my final pre-dive check; 2 breaths from my primary regulator and 2 breaths from my secondary. The needle on the SPG should not move. If it does, it indicates that the cylinder is not fully open.

The Swift transmitter updates every 5 seconds or so (according to the manual). This will not show the ”needle drop” that an SPG would show.

I have the same setup and do the same thing, though I also wait to see the small drop in PSI from the AI. Always want to make sure everything is communicating before splashing (even though it has always worked).

 

[Failed captcha]

The thread title caught my attention.

Would the answers be different if OP wasn't just asking about Shearwater AI? Do certain transmitters give similar differences in answers?

I'm near a decision to buy my wife a Perdix and two transmitters is why I ask.

 

[BlueTrin]

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[Belzelbub]

Would the answers be different if OP wasn't just asking about Shearwater AI? Do certain transmitters give similar differences in answers?

I'm near a decision to buy my wife a Perdix and two transmitters is why I ask.

Possibly, yes.

The PPS transmitters are quite simple. They turn on when pressure is sensed, and turn off when pressure drops to near sea level ambient. They just broadcast to wherever. The computer looks for a specific string (Serial number of transmitter) and if found, displays that. The Shearwater Swift is largely the same, but it listens to the frequency and can vary the interval if interference is detected. Really only an issue if you have several transmitters.

Some other brands have "power saving" features that will power down the transmitter if it doesn't detect a change in pressure after a certain time. I put power saving in quotes as it's really not needed. The PPS transmitters can last a real long time on a battery. I think they are rated at 300 hours. Garmin actually switches transmission modes above and below the water. All that switching on/off, switching modes gives chances for something to not work. Electronics most often fail on startup, so the simple on/off with no other switching makes a lot of sense.

 

[VikingDives]

Yes, I dive with an SPG. It's in my save-a-dive kit along with backup batteries.

 

[NAUI Wowie]

It depends.

With a Shearwater you can go to the voltage page which give a much better idea of the battery state, especially if you’re noting the battery voltages on each build. SAFT batteries suddenly drop and this doesn’t show up on the battery "gauge" widget.

Of course if the computer failed, you’d just swap to one of your backup computers.

If the AI battery failed during a dive it’s a little inconvenient on a rebreather and not a reason to call the dive. AI is somewhat more important on open circuit, hence many would back up AI with a visible SPG

Could you translate that to peasant scuba lingo?

 

[Wibble]

Could you translate that to peasant scuba lingo?

Computer fails, you use your backup computer.

Principle: if it’s important you bring two. Or three.

 

[Larryjd1]

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I don't think I'll be doing do this, but I'm curious how you position them on the tank? Band the transmitter straight down and simultaneously bend the SPG up towards the valve? Band it all downwards until you encounter a transmitter failure and then re-jigger the SPG to a viewable position? Something else? Any pictures?

 

[gordonscuba]

I don't think I'll be doing do this, but I'm curious how you position them on the tank? Band the transmitter straight down and simultaneously bend the SPG up towards the valve? Band it all downwards until you encounter a transmitter failure and then re-jigger the SPG to a viewable position? Something else? Any pictures?

On a recreational single-tank set up, I dive a standard long-hose configuration with the mechanical SPG clipped to the D-ring on my left hip, and additionally, a transmitter threaded directly into the first stage.