Questions about AI Transmitter

[Joneill]

I have breathed my cylinder down to 170 psi with normal functioning of the transmitter and computer. I have no reason to believe they would not continue to function at a lower pressure. This is with an Oceanic VT3 and a PPS transmitter
View attachment 507836

That's one long dive and great RMV!

 

[tursiops]

I tested the turn off pressure by shutting off the tank valve, there still is pressure on the first and second stage, then gradually press the purge with tiny presses to see when the signal from the transmitter is lost, at which time the VTX will flash the pressure amount . There is an SPG on there as well.

I just tried the experiment again, this time it went to about 150 PSI before loosing the signal, but it may be loosing the signal for another reason, maybe I'm holding the VTX at a bad angle. I'm sitting in my chair with the VTX on my knee and the tank/transmitter next to my knee, well within 24" so should not loose the signal. Need to try it again I guess. Sorry about the false alarm.

I miss-stated things a bit, the manual did not have the 10 minute turn off, as I searched around I guess I got both the 300 PSI and the 10 minute turn off from this FAQ:
FAQ - How far will my transmitter transmit air pressure to my wireless computer?

I do not believe that FAQ is correct. The (gray) transmitter for sure reports every 5 s, not 15 s, and I do not think it shuts off after 10 minutes of no pressure change while pressurized (as you discovered), but rather after 2 minutes of having zero (<50 psi) pressure on it. it won't be the first time Oceanic has provided faulty info.

 

[Manatee Diver]

That's one long dive and great RMV!

Go out with @Scuba_Jenny at BHB, you can dive until your tank is empty.

But another example of a PPS transmitters going below 300psi.

 

[Joneill]

Go out with @Scuba_Jenny at BHB, you can dive until your tank is empty.

View attachment 507848

But another example of a PPS transmitters going below 300psi.

That's impressive as well - but an RMV of 0.363 still beats an RMV of 0.38

 

[scubadada]

That's one long dive and great RMV!

My average RMV over the last 1260 dives is 0.36 cf/min. I often do a bit better than that, I think this is my lowest RMV

 

[DanSinks]

If you intentionally go below 300 psi, knowing exactly how far below it you are is not going to help you much! You should already be on a steady ascent to the surface ready to do a CESA if you run dry. Howver, if I get a chance, I'll mount my reg and purge it down to see how low it detects.

Until I get a lot more experience with this AI VTX and transmitter, I will keep my console with SPG. I need to understand it thoroughly in order to trust it. There is no good reason for me to come back to the boat with 300 PSI or less, depends on the circumstance but most times it will be at least 500.

I appreciate all the good replies from people on this, I've learned some things from it.

 

[Joneill]

My average RMV over the last 1260 dives is 0.36 cf/min. I often do a bit better than that, I think this is my lowest RMV
View attachment 507872
View attachment 507873

That's a crazy low RMV. Over 120 logged dives, I've been steadily improving and now typically around 0.41-0.45 with my lowest at 0.38. Any tips on how you acheive such a low RMV?

 

[Joneill]

Until I get a lot more experience with this AI VTX and transmitter, I will keep my console with SPG. I need to understand it thoroughly in order to trust it. There is no good reason for me to come back to the boat with 300 PSI or less, depends on the circumstance but most times it will be at least 500.

I appreciate all the good replies from people on this, I've learned some things from it.

That's a good plan - redundancy is good, especially when using new gear!

 

[scubadada]

That's a crazy low RMV. Over 120 logged dives, I've been steadily improving and now typically around 0.41-0.45 with my lowest at 0.38. Any tips on how you acheive such a low RMV?

I've been diving since I was 16 years old. My gas consumption has always been good, I attribute much of it to having been a competitive swimmer from the age of 4 through high school. My breathing pattern underwater naturally evolved into a slow, relatively deep inhale, a brief pause, a slow exhale, followed by an immediate inhale. If you pay attention, this is the opposite to how you breathe on land. Works for me.

 

[NAM001]

I had an Aeirs ai computer. 2-3 of them any way. and I believe they turn on at 50 psi. The real question for me is . Is the same depth sensor used to shut down or is it a separate sensor. If separate then you can not use the AI INPUT to say when it shuts off. All and I mean ALL my AI units after a year or there abouts got a 300# error in them. That was proved by using an independant tank gage. In that case one would be inclined to think that it turned on at 350 psi and not 50 psi. My Ai errors varied from being at the high end low end or over all. The one most noticed is on the high end when you know you have 3000 psi gage and the ai reads 2700. I don't use AI any more because of that and the cost of refurbing them. 100$ or more each time. I hope they have improved over the years. The Aeris and Oceanic are the same I think. Also when you vent the reg you have to do it again in a few minutes becasue you will get 50# again and it will start transmitting. All you have to do is remove the reg and listen to the air slowly drain from it through the regs tank fitting. I ultimately had use an spg with the AI.