The Cobra does record your usage during the dive the problem is that SDM software does not show you that info. It only gives you starting pressure and ending pressure and an a linear graph between the 2 points. If you use a different software to extract the info from the computer you will see actual air usage during the dive. ...
Hmmm ... I don't actually know that's wrong, but it's quite a surprise to this Cobra user. I base my understanding on the following:
1) The Cobra user's manual Specification page (page 65) describes the Logbook/Profile memory as "records the maximum depth of each [sampling] interval". No mention of tank pressure.
2) The description of the PC interface (section 4.1.3, pages 45-46) lists the data transferred. This includes "depth profile of the dive" and "cylinder pressure at the beginning and at the end of the dive (i.e., pressure drop deltaP during dive)" among other data, but nothing about any other pressure profile data.
3) The on-screen access to the log available through the Cobra buttons and screen (no PC needed) includes delta-P, and then in screen 4, a continuous scrolling of the profile intervals. During this profile scrolling, only depth is displayed; tank pressure is not. This is based on the manual page 44, and also I just took out my Cobra and looked at my most recent dive. Only depth, no pressure or temperature. If it was in the history, there's certainly room on the screen to display it. Just sayin' ...
4) At papers:suunto_vyper [Markus Fritze (MMM)] the author (Pascal Pellmont if I've got that right) has posted his reverse-engineering of the protocol. The description makes clear that the profile records only depth, in one byte per sample. There are some special codes injected in the profile to record "events" like alarms of several kinds, but no tank pressure info appears except for start/end of dive.
5) DiveLog the s/w I use, only gives me start and end pressures. I expect Mark wouldn't hide pressure profile data if it was available.
All that said, Suunto doesn't publish the protocol. Maybe the author of Macdive has figured out some secret access method nobody else has. But I'm skeptical. Are you sure you're not talking about a Cobra II or some other model? Can the author of Macdive comment?
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