Ok, playing the Devil advocate, I dare to ask: who need a back-up computer for rec dives
As for AI, what is the point? Don't you (general "you"
)know your approximate consumption and is to watch the gauge 4 or 5 dives during the dive, a difficult task?
Keep the easier one to read for yourself and give the other to your daughter.
I agree entirely. Two computers for rec diving are not only unneeded, but even a trouble. I always appreciated the KISS approach (keep it simple stupid). What you don't have, cannot break. Use the same approach on my offroad vehicles (pickup and motorbikes). The simpler, the better.
So I would keep the good computer (the Peregrine in your case) and give the other to your daughter. Or, better, buy another Peregrine for her... And be happy with your old-style SPG. I usually use my one only 3 times for each dive:
1) On the boat, when I open the tank, and I check that there are at least 200 bars (my tank is a 15 liters, 232 bars) - at that point I also test breathing, and check that the SPG pressure is NOT dropping during berating, if it drops, it means there is some obstruction in the valve or in the metal filter of the reg... Doing such test with an AI computer is not so easy!
2) At the end of the dive, when I think is more or less time to end the dive, I check the SPG for having an idea of my air consumption, usually it is yet around 120-130 bars, sometimes it is around 100, which means I did make a lot of effort.
3) After surfacing, and hence after doing the safety or deco stops, I check a third time, just for being sure that there are at least 50 bars left, as planned.
My wife uses the same tank as me, and she has much less gas consumption, so in practice she only checks the initial pressure, and then she forgets entirely about her SPG. She usually surfaces with more than 100 bars, often 120. I think that all the problems reported here on SB about people risking to finish their tank (and hence needing to check their SPG often) is due to the bad idea of using too small tanks, such as those crap AL80, which in fact are almost unknown here.
