Uncle Pug:
Slightly off topic but since the issue was raised... ascent indicators introduce unnecessary hysteresis. Beyond that and IMO even more important to consider:
Using an ascent indicator and/or alarm to assist in controlling ascent will, for the majority of divers keep them from ever developing the skill to do so without it.
For those who have developed the ability to control their ascent going back to computer assisted ascent indicator/alarm will most likely prove to be skill-degrading.
This will probably be of no consequence until something goes sideways in a dive and the diver's attention is diverted from the indicator and the alarm only adds to the confusion (if heard at all.)
Being able to sense your position in the water column and automatically control it while your attention is demanded by other matters is not a trivial skill.
Shallow water practice of neutral bouyancy with your eyes closed greatly facilitates learning to sense small changes in depth. Practice managing multiple tasks under pressure while maintaining position and depth takes it to the next level. Multitasking under pressure with your eyes closed takes it a step beyond that.
Perhaps, but maybe my sinuses and eustaian tubes etc. aren't the same as yours or even "typical", but I do not have any medical condition to contraindicate diving.
I doubt I could have used your methods to any degree of success on our recent rip to Saba while performing the pinnacle dives for example. Fairly quick descents were in order due to the diving style for the pinnacles and as a result I only did a few of these type dives due to not clearing adequately for my physiology on a descent. All ascents and any later descents I made during the trip were all performed with assistance from the mooring line even when on the lee side of Statia and checks made of the ascent meter when ascending.
While what you mention is agreed not a trivial skill I am unsure whether you are indicating anyone using other means should not be diving.
Diving Preacher, you may want to check the detail of your dive computer's ascent alarm settings. FYI, the first alarm setting on the TUSA IQ-700 is at 50% of the max "safe" speed for the depth range so there is ample warning during the approach to safe speed. If the "safe speed" is exceeded, all the segments are made visual and a separate "Slow" graphic is displayed. Thus, it is possible to have an audible alarm associated with ascent speed without actually exceeding the DC's "safe speed" for that depth. If it only alarmed when the speed was exceeded and not prior, it wouldn't allow opportunity for adjustment of your speed. This would be about as useful as a radar detector that beeped to warn you at the same time the patrol car's top lights illuminate your rear view mirror - and was the basis for somprevious generation ascent alarm programming.
UP, I'd be happy to chat off-line or via PM on the hysteresis issue you raised. I would like to revew the data and assist with my input from formal education and experience in control devices and human machine interface.
I would tend to agree with Charlie99's last paragraph above this post. The whole is more than the sum of its parts.
I have mentioned before I am a data freak and lack of data would increase my personal discomfort more, when discussing use of SPG's with double tanks, and I have posted I do use redundant electronic devices. But this still doesn't preclude use of a mooring line in my case just because I carry electronics.
