I'll take a mechanical gauge that's out at the low end, any day of the week, over a digital not working...
I'll still be diving with the mechanical... ( 200-300 psi out is not a big deal)
With a digital I can't really unless you like exciting dives..
Yes I expect a digital and mechanical gauge to last 30 year, in storage
One needs a battery, and one needs a spool. No big deal,
I'm not sure I understand.
How is an inaccurate SPG better than a digital one? Especially if the SPG becomes "sticky" over time, so you don't actually realize that it is no longer accurate, like it used to be?
I'm taking you to mean that if you are ready to dive and you have a choice between discovering that your transmitter has just totally died or your SPG is 300 psi off, you'd rather have the SPG because you can still dive?
That is totally understandable.
But, it has not really been realistic, in my personal experience. I did have a transmitter once that was dead just when I was about ready to dive. It had been left on a tank with the gas on for a while and that prematurely killed the battery. But, when that happened, I pulled out a replacement battery, put it in, and went diving. Still much preferable, to me, to an SPG that is not accurate.
Worse, though, is your implication that you would KNOW that your SPG was off by 200-300 psi. Part of my point was that you could easily not know that. On the other hand, you will clearly KNOW when your transmitter is dead.
For purely diving, would I care if I saw approximately 2500 or if I saw exactly 2487? No....
What does that added cost really give me? I really use a gauge like a "fuel gauge", and base my diving on full, half, quarter.....
Sometimes I wish that my Perdix had a "analog" style display for pressure for the quick assessment...
The added cost gives:
- Warnings/alarms on your computer if your gas gets low. You don't need that, because you always monitor your tank pressure so well... except for that ONE time when sh!t happens and you get distracted and are maybe dealing with some kind of emergency or something. The alarm on mine definitely helped me once when I had a freeflow I was trying to resolve and not watching my tank pressure. I had no idea I was losing my gas as quickly as I was. It was not a life-threatening situation. I was carrying other options. But, my AI alerted me to critical low pressure and I thumbed the dive and got back to the surface before I ran out. Had I run out, I could have switched to a different gas source and been fine - but it would still not have been as pleasant for me as being warned and thumbing the dive before I ran out.
There are lots of reasons people run out of gas. I am just not convinced that a significant one of those reasons is that they became dependent on their computer/AI to warn them and then their AI broke, failed to warn them, and then they ran out of gas. I suppose that might be an interesting thread to start. Take a survey to see if anyone knows of that actually happening to someone.
- Very precise and fairly accurate data on your RMV. I have my gas consumption data from every dive I've ever done. I know what my RMV is when I'm stting perfectly still doing nothing. I know what it is when I'm swimming slowly - in a wetsuit and single tank, in a drysuit and doubles, etc.. I know what it is when I'm working hard. Etc.. I know if it is changing over time. I know what it is on the first dive of a trip and how it changes over the course of a trip.
Sure, I could plan my dives based on my worst case gas consumption and 90% of the time have an extra big margin for error. But, why wouldn't I prefer to have more accurate data for planning my dives?
- ability to monitor gas in a HUD/NERD so you can keep track of it without having to take a hand off your camera rig.
- less clutter on your rig. One less hose. One less thing clipped to that D-ring (or one less D-ring on your rig).
- attached directly to your first stage, there are several less places where you could have a failure, and a failure is far less likely to result in actually losing gas. SPGs have several more ways they can fail that results in you actually losing gas.
