DIR SPG(s) config with isolation manifold?

[jplacson]

Just wondering... the newer AI computers have wireless transmitters. How come these aren't used as a primary SPG, with a traditional SPG on the left side as back-up as well? Seeing as that the wireless system would offer the advantage of a 2nd SPG without the hose issues.

 

[salty]

Just wondering... the newer AI computers have wireless transmitters. How come these aren't used as a primary SPG, with a traditional SPG on the left side as back-up as well? Seeing as that the wireless system would offer the advantage of a 2nd SPG without the hose issues.

Once agan you gain nothing but grief. If you have to close a valve that will no longer allow you to use the pressure gauge you are ending the dive. why would you still need the AI gauge. Besides the AI transmitters look as though it wouldent take much to knock them off.

 

[MikeS]

Not really. A second gauge will read exactly as the first one. Your gaining nothing and introducing more failure points, e.g. O-rings, hose and the gauge itself.

Perhaps this is a matter of semantics but of course you gain something, that’s obvious, and not the question. The question is: “is what you gain worth the cost.”

You gain redundancy with the isolation valve open, as well as a confirmation that the valve is open if they read the same as you use some of the gas. Additionally, you gain the ability to monitor both sides of the isolation valve.

The cost(s) associated with this are additional complication and failure points.

What I think MHK pointed out is that based on DIR gas management practices the value of what you gain is minimal so therefore does not warrant the cost.

Mike

 

[Spectre]

as well as a confirmation that the valve is open if they read the same as you use some of the gas.

With the guage on the left post, and your primary reg on the right post, you get that anyway.

 

[orca]

Mike,

Your comments are the smaller of the issues. The larger picture is that a diver should be taking 5 minute snap shots of their dive. In the course of those snap shots they should be estimating in their head how much gas they used, and how much they have left. Let's assume for arguments sake, and to make the math easy, that you normally use 100psi per minute. Assume you start your dive with 3000psi, at 5 minutes your tank should read 2500psi, at 10 minutes it should read 2000psi. If you are using doubles, and you of course checked your starting pressure before you got in the water, when you looked at your SPG at 5 minutes it should read 2500psi, if it doesn't then you can safely assume that you isolator is closed. Normally, we teach that you do a flow check as you start the dive, so the isolator should be caught then, but if for some weird reason you didn't catch it when you geared up, you didn't catch it during your flow check, you would then be able to catch it, when you checked your gauge every 5 minutes.

Certainly the added failure point is of one concern, the financial considerations are of less importance because if it's needed then money shouldn't be the issue, but the larger point is that it's not needed if you have a diver that turns his brain on during his diver as opposed to a diver that uses devices instead of paying attention..

Hope that helps..

Later

I understand the amount of gas we used at different depth are different due to changes in pressure. If we're diving at a single depth, then the estimation is fairly simple, but what if we're doing a multi-level dives (recreationally)?

Does it mean that I would need to know what is my consumption at different depth?

 

[MaxBottomtime]

Perhaps this is a matter of semantics but of course you gain something, that’s obvious, and not the question. The question is: “is what you gain worth the cost.”

You gain redundancy with the isolation valve open, as well as a confirmation that the valve is open if they read the same as you use some of the gas. Additionally, you gain the ability to monitor both sides of the isolation valve.

The cost(s) associated with this are additional complication and failure points.

What I think MHK pointed out is that based on DIR gas management practices the value of what you gain is minimal so therefore does not warrant the cost.

Mike

Redundancy is not necessarily a gain. You should have the isolator open while diving, so a single spg will read each tank, or both sides as you said. Having a second spg serves no useful purpose. The gauge on your left post gives you an accurate reading if the isolator and each valve are open. In the unlikely event that you need to isolate and close the left post you would be aborting the dive and the amount of gas you have is moot. If you don't have enough to complete the ascent, an spg won't give you more gas.