Ascent Rate Gauge Question

[Curly]

I've done about 10 dives on a new Oceanic Data Plus Navcon, which I am pleased with.

With one exception.

When I review dives in "log" mode. two of the dives indicate that I actually ascended too quickly (according to the "variable ascent rate indicator"), when I am sure that I did not. In fact, the most recent instance was on my most recent dive. It was a boat dive on a lake, with a shallow max depth (32 ft.) with the majority of the 47 minute dive spent in the 20 ft. range. Since night was falling and visibility decreased, I paid close attention to my console duing ascent to ensure a safety stop and nice slow ascent. The ascent rate indicator was in the green (if any arrows were showing at all) and hit the yellow once. But later, when reviewing the dive in log mode to check the time, I noticed that it had me "maxed out" (all arrows blinking) on the ascent. I know that this is not the case.

Anyone else have similar experience?

Many thanks.

 

[Rockhound]

the same thing with my computer and it worried me until I noticed that just by raising my arm too fast, I triggered the ascent warning and made the display flash (I have the little USD version of your computer).

Upon reviewing the recorded dives, several of them showed too fast an ascent, although I tried to be very careful and feel confident my true ascent rate was slow enough. In hindsight, I think this "arm/computer ascent" glitch was the source.....

 

[Curly]

Thanks -- that could also be part of it. As I mentioned, I was watching the console closely, and so had it unclipped from my BC. But I wonder if the 2-foot rise/drop from where it normally hangs to the space in front of my face would trigger that reading. Weird. Like I said, there were occasionally visible arrows -- one or two -- on the way up, but never four or a full five (like it shows for that dive in log mode). At one point, I did a little "bounce" between about 14 & 19 feet (watching my buddy wrestle briefly with the flag line). Perhaps this could've triggered it.

 

[miked]

Hi Curly,
The "bounce" you mentioned could certainly have an effect on what the VARI showed, particularly if the sampling happened to be taken at the "right times. Additionally, I agree with what Rockhound said, and with your comment about picking up the wrist or console. My Oceanic computer ( a recently "dead" Data Plus) would show the same thing.
Additionally, in a situation where you lift the console while you are ascending, you might get an "indication" of a rate that is double the actual rate of ascent [=your rate + the console's rate relative to you, as you lift it]. Also, remember that the log mode ascent rate indicator shows, to quote the Data Plus Manual "the maximum ascent rate at any point in the dive" (# of arrows, anyway) without regard for the length of time that you were at that rate.
BTW, I just got an Oceanic Versa Pro (to replace the Data Plus), and in its manual, it indicates that, in log mode, the VARI will show " the maximum ascent rate maintained for at least 4 consecutive seconds during the dive." The "4 second" bit is new, and would address the "arm lift" situation of which we speak.
Hope this is helpful,
Good luck,
Mike

 

[Curly]

Many thanks for the information. That makes sense. Like I said in the follow-up above, there was a "bounce" where I went up & down a few times between ~19 & 14 feet while -- and I did go back up to 14-15 ft. for a safety stop faster than the rest of the ascent. That, coupled with the console motion, could explain the five flashing arrows.

Overall, I am very pleased with this computer. Works well, easy to read, and the price was right.