Transmitters?

How many of you rebreather divers use transmitters on your O2 and DIL bottles?


  • Total voters
    54

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I doubt anyone (on CCR) is "continually" monitoring their gas. But, I do check mine usually a couple of times during a dive. It's peace of mind that I don't have some leak that I didn't realize I had.

A reasonable answer. I can see the benefit of that.

If you don't need to check your dil and O2 pressures during the dive, then you don't need AI or even SPGs, right?

No, that's not what I said. You need to check if you have a boom. Or if you do something unplanned, and use a lot more gas than anticipated.

So I have that capacity with SPGs, but it's so rare that I don't need to go out of my way in terms of cost, clutter and screen real estate to make that data so readily available. If I have a boom, I grab my SPG and look at it. Otherwise, it stays out of the way.


Why not check your dil and O2 cylinder pressures just before you install the cylinders on your CCR, using a separate pressure checker? Thus eliminating the potential failure points associated with the HP hose, SPG, et.?

Some people do this - button gagues on the first stages that you check only before donning the rig. While I don't do that myself, I can see the argument for it. You can tell that you are completely OUT of O2 or Dil without a gague, right? And whether you have a gauge telling you have no O2 or if you just can't keep your PO2 up, you are going to do the same thing, right? Of course, once you have checked that it's not just a valve rolloff...

So the question is not about being out of gas, but how will watching your dropping O2 or dil help you? Are you going to run your dive by watching how much gas you have left? That's OK if you are, it's just a very different type of CCR dive planning than what I'm used to.


If you do need SPGs, then why not have them showing on your computer display instead of having to look at physical gauges?

Because of the reasons I outlined in my post.

As I think I posted before, I have appreciated being able to look at my gas consumption data after a dive, to see where during the dive I used my dil. When I can see that I used dil at the very beginning, up until I got to my max depth, and then I used no more during the rest of the dive, then I know I've done well. If I see that I occasionally used some more after getting to max depth, then I know I need to review what I was doing and figure out if I can do better. Was my mask leaking, causing me to need to clear it and waste dil? Or was it just that I was doing some up and down stuff on the bottom? Or something else?

OK, but I kind of know when I'm losing dil because of mask clearing or a lot of up and down. But I see your point. Not enough to change the awesome JJ design, though! :D
 
I don't need to go out of my way in terms of cost, clutter and screen real estate to make that data so readily available.

We are in agreement that we do want to have an SPG we can consult during the dive. That was kind of my point in talking through not having them.

Yes, AI costs more. To me (and, I suspect others using AI), one of the benefits is LESS clutter. Clutter is not a cost of AI. It's a benefit. My transmitters are far less "in the way" than 2 SPGs (that I could check during a dive) would be.

Screen real estate is, I think, a non-issue. You do not HAVE to give any screen real estate to your pressures. You CAN have it where it's something you would just right-tap to scroll over to see, if you want to check your pressures.

So, cost? Yes, an issue. But, compared to the cost of a CCR and all that goes with it, the cost of 2 transmitters is pretty near trivial.

Clutter? Not an issue, actually a benefit. One that is worth the extra cost, to me.

Screen real estate? A total non-issue.

Additional benefit(s):

Being able to view (after the dive) your momentary usage at any time during your dive. Whether it's dil or even looking at how much O2 you were consuming during different phases of the dive.

You CAN configure your NERD2 (if using one) to show your tank pressures at all times (IF you want that).

Less failure points that could result in a gas loss. I.e. no HP spool to blow an O-ring, etc..

Additional "costs":

You have to change batteries. You have to remember to turn off your gas and depressurize your lines to keep from prematurely killing your transmitter batteries.


So, we want to have SPGs we can check in the water. It's just down to which kind you want (mechanical or electronic). I'll take Less Clutter for $800, please, Alex. :wink:
 
We are in agreement that we do want to have an SPG we can consult during the dive. That was kind of my point in talking through not having them.

Right, I don't believe that I would dive without them, but there is a non-trivial argument for the fact that you can dive CCR that way.

Yes, AI costs more. To me (and, I suspect others using AI), one of the benefits is LESS clutter. Clutter is not a cost of AI. It's a benefit. My transmitters are far less "in the way" than 2 SPGs (that I could check during a dive) would be.

Well, I guess. If I actually checked my SPGs during a dive, that would be more physical things on my rig than the transmitters.

Screen real estate is, I think, a non-issue. You do not HAVE to give any screen real estate to your pressures. You CAN have it where it's something you would just right-tap to scroll over to see, if you want to check your pressures.

Makes sense.

So, cost? Yes, an issue. But, compared to the cost of a CCR and all that goes with it, the cost of 2 transmitters is pretty near trivial.

Clutter? Not an issue, actually a benefit. One that is worth the extra cost, to me.

Screen real estate? A total non-issue.

I guess this also depends on the actual CCR design. But with inverted tanks, I have seen a situation where the transmitter was damaged because it sticks out and can potentially take the weight of the rig if the tank slips in the band.

The clutter thing was more about my preference for the JJ design over the - for example - rEvo design, with the SPGs tucked away but accessible, instead of being in front of the rig, competing for space with gas blocks, can lights, and whatever else you clip off to your D-rings. Clearly, transmitters don't involve clutter at all. I suppose my point above is off topic for this thread.


Additional benefit(s):

Being able to view (after the dive) your momentary usage at any time during your dive. Whether it's dil or even looking at how much O2 you were consuming during different phases of the dive.

You CAN configure your NERD2 (if using one) to show your tank pressures at all times (IF you want that).

Less failure points that could result in a gas loss. I.e. no HP spool to blow an O-ring, etc..

HP. Not LP. But yeah, with a small tank that's low, even an HP leak can add up over time...!

Additional "costs":

You have to change batteries. You have to remember to turn off your gas and depressurize your lines to keep from prematurely killing your transmitter batteries.


So, we want to have SPGs we can check in the water. It's just down to which kind you want (mechanical or electronic). I'll take Less Clutter for $800, please, Alex. :wink:

I'll take less bandwidth and more simplicity, but I do appreciate your points, and you are not wrong. Is it $800 each or for two?
 
So the question is not about being out of gas, but how will watching your dropping O2 or dil help you? Are you going to run your dive by watching how much gas you have left? That's OK if you are, it's just a very different type of CCR dive planning than what I'm used to.
I've turned a cave dive early after burning through more O2 than I expected to (swimming hard and lots of venting on the sawtooth profile). I've also watched my O2 very carefully on another dive and let my ppO2 lag a bit in an effort to not add it only to dump it 3 mins later.

If you always start with a full O2, and only do square-ish wreck profiles, or your definition of sawtooth is up and down between 55 and 95ft in Ginnie, then sure diving without gauges starts to sound quasi compelling.
 
I'll take less bandwidth and more simplicity, but I do appreciate your points, and you are not wrong. Is it $800 each or for two?

For 2. The new Shearwater transmitters are $395 each, so that would be worst case.
 
I've turned a cave dive early after burning through more O2 than I expected to (swimming hard and lots of venting on the sawtooth profile). I've also watched my O2 very carefully on another dive and let my ppO2 lag a bit in an effort to not add it only to dump it 3 mins later.

If you always start with a full O2, and only do square-ish wreck profiles, or your definition of sawtooth is up and down between 55 and 95ft in Ginnie, then sure diving without gauges starts to sound quasi compelling.

I'm not a cave diver, you are correct in your assumption. I guess I would be concerned about entering a cave with a limited amount of O2 along with the possibility of significant variability in workload. As far as dil, unless you were mapping a new cave, you would know what how sawtooth it is ahead of time, so less likely for there to be a suprise WRT dil.

I mean, it sort of comes down to the choices you make before the dive, right?

So are you saying that normally to do a dive like this you would want full O2 and dil bottles, but in this case you will do it with a partial fill and use your SPG to control the dive? Not saying that's wrong, I don't know enough about cave diving to have an intelligent opinion. And like I said, I'm always happy to learn. But that seems like an unnecessary risk, although of course there is always enough bailout, right?
 
I'm not a cave diver, you are correct in your assumption. I guess I would be concerned about entering a cave with a limited amount of O2 along with the possibility of significant variability in workload. As far as dil, unless you were mapping a new cave, you would know what how sawtooth it is ahead of time, so less likely for there to be a suprise WRT dil.

I mean, it sort of comes down to the choices you make before the dive, right?

So are you saying that normally to do a dive like this you would want full O2 and dil bottles, but in this case you will do it with a partial fill and use your SPG to control the dive? Not saying that's wrong, I don't know enough about cave diving to have an intelligent opinion. And like I said, I'm always happy to learn. But that seems like an unnecessary risk, although of course there is always enough bailout, right?
Well that's a bunch of assumptions...

How about you get in the water and your 2L O2 bottle is at 2500psi/175bar? Would you just cancel the dive and have everyone de-kit and haul your O2 back to (somewhere) to get it topped off? Or perhaps it's full but you get in and holy hell its flowing like crazy town? That's going to be a ton of work. In either case, most people just do the dive, 2L*175bar = 350L of O2 which is "7hrs" of O2 at 0.75L/min - not counting what ends up vented. The vented fraction is not really something you can precisely or accurately plan even in a known cave.

Anyone saying you don't need gauges is basically diving the same tourist caves over and over so they "know" they will finish with enough. Although smart cave divers have a way to inject offboard O2 from their O2 BO bottle so they can deco on the loop if they ran out by some sort of surprise. There is BO and in many FL tourist caves where hot dil like 32% is used you can SCR out. Both of which seem like a foolish tradeoff to just having an O2 gauge.

On the other side, standard cave diving dil is offboarded anyway. Cave diving on 2 or 3L of dil is a recipe for running out even if its plump-ly full at the start. And I can pretty much guarantee you will run a 3L dil bottle empty in a cave like Hole in the Wall.
 
I didn't say anything like that, and I didn't make any assumptions.

I asked you about CCR cave diving planning, because I don't know anything about it. I asked if you would use your SPG to save a dive by limiting your travel based on your onboard O2 reserves. If that's what people do in that situation, fine. I specifically DIDN'T say that it was wrong.

Not sure what you mean by the first scenario, but I would think that - cave or otherwise - how much O2 you have in a bottle would be the kind of thing that you could know well ahead of time, before everyone gets kitted up, especially for big dives like this.

I certainly understand that going into a cave with that many variables, you should definitely have a way of tracking your O2 reserves - didn't mean to suggest otherwise. Was just responding to Stuart's straw man thing implying that I was suggesting no SPG of any type.

Unless you are a military diver, all dive plans are optional. So if planning on the fly based on real world consumption is the way you do it, I understand. Just wanted to learn.
 
There are lots of people here with more experience than me who are voting for transmitters, and I'm always willing to learn. But other than a boom drill (or an actual boom), not sure what the scenario is where I need to continually and conveniently monitoring gas pressure for a CCR dive.

I'm also aware of the limits of cognitive bandwidth - taking up screen real estate with tank pressure on my NERD or controller seems unnecessary to me.

But as I said, always happy to learn.
Simple answer for me is I am a numbers geek, IRL I am a engineer and I love that I can track gas usage and play with the numbers. I have the vision 2020 handset on my APD and I carry the perdix AI (set to CCR) with the transmitters. Now that I can have 4 transmitters, my bailout tanks are part of the dive profile in my logs. Yes I still keep logs, electronic but logs.
 

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