That's fine, but why exactly are you monitoring your pressure? At some point in the process, you have to interpret what that pressure means, and when (if?) you do that, you have convert that pressure to a volume.DA Aquamaster, if you can show me where and how to set the tank size on any SPG, I will confess to having lost what little sense I was born with.
I don't know about you, but I was trained to monitor my "pressure" using an SPG (submersible Pressure gauge) but, hey, if you think pressure is meaningless, then have at it.
We will have to just agree to disagree.
Come to NC and we'll go diving. I'll hand you a reg and an SPG and you tell me how long you'll want to stay on one of the 110 ft wrecks here. What I won't tell you is how large the tank is - it might be an X8-130 under filled to 3000 psi with 113 cu ft in it.
Of course the reg and SPG might also just be attached to a 6 cu ft pony strapped to an empty tank on your back, but hey, by your standards you're just fine as you are trained to look at your SPG and note the psi, and from your perspective, the SPG will say 3,000 psi when you look at it and start your descent to 110' so you'll be good to go.
Obviously tank size is a critical factor to making any sense at all out of what the SPG tells you and what "3000 psi" actually means to you on the dive.
Personally, I was trained to look at the SPG, and then interpret what the number actually means.
MY SPG tells me an awful lot more than just "PSI". I was trained to note if the needle actually moved since the last observation and to compare what it tells me (the pressure but more importantly the remaining volume of gas in the tank, once I factor in the tank size) to what I expect it to tell me at that point in the dive based on my anticipated gas use at the depth, time and workload involved. And if the reading does not match my estimate, it tells me something may be a miss.