Looking for a nice Air Integrated, liberal decom(or able to change liberal/conservativeness) computer. Open to literally anything.

[Gandalf-the-Diver]

uh oh- 2 shearwater perdix ai with transmitters? 3.5k CAD, or about 2.8 USD

New, or get a Peregrine, which would make a nice back up to a Perdix, later.

 

[Blackcrusader]

New, or get a Peregrine, which would make a nice back up to a Perdix, later.

Or start with the Peregrine ( No AI though ) and then get a Perdix AI when he wants to do technical diving.

 

[Gandalf-the-Diver]

Or start with the Peregrine ( No AI though ) and then get a Perdix AI when he wants to do technical diving.

I started with a Peregrine. I have 245 dives on mine. No Perdix yet.

 

[tursiops]

There’s a long thread on SAC vs. RMV somewhere on here.

SAC vs RMV, revisited

ScubaBoard and the diving literature is full of references to these two terms, without any agreement as to what they mean. One ScubaBoard thread from a few years ago that tried to sort this out, unsuccessfully, is SAC vs RMV - What is standard?. The problem is there is no authority as to what...

scubaboard.com

 

[scubadada]

What’s RMV?

There’s a long thread on SAC vs. RMV somewhere on here. There is some debate, but the generally accepted answer is:

SAC is Surface Air Consumption, and is measured in PSI/min.
RMV is Residual Minute Volume, and is measured in cu ft/min.

Both are a measure of consumption at 1 atmosphere. With SAC, you can’t transfer to a larger or smaller tank as the rate you consume PSI will change. With RMV, the rate is in actual volume consumed at the surface. With either SAC or RMV you would need to convert for depth to figure out how long a given amount of gas will last.

Or for the rest of the world

SAC is Surface Air Consumption, and is measured in bar/min.
RMV is Residual Minute Volume, and is measured in L/min.

It's actually Respiratory Minute Volume

Take the SAC calculated by your Perdix AI with transmitter and multiply by the tank factor to get your RMV. You can make the calculation manually, follow the links in the @BLACKCRUSADER post Looking for a nice Air Integrated, liberal decom(or able to change liberal/conservativeness) computer. Open to literally anything. After you have your RMV for a good number of dives, you can calculate the average. This will reflect your usual gas consumption under the conditions that you usually dive

I have my RMV for my last 1669 dives, 0.36 +/- 0.04 cu ft/min (mean +/- std dev). So, 95% of my dives would be expected to be between 0.28 and 0.44 cu ft/min. The actual range of all of these dives is 0.26-0.63 cu ft/min.

Here is an example of the RMV calculation from my Teric and the Shearwater Cloud This was with an AL80 cylinder.

12.7 psi/min x 77.4 cu ft/3000 psi = 0.33 cu ft/min

 

[Belzelbub]

It's actually Respiratory Minute Volume

Yeah, that would actually make more sense. Not sure why I wrote Residual.

 

[ScubaBadger32]

Yeah, that would actually make more sense. Not sure why I wrote Residual.

In your defense, almost every single calculation has to do with RESIDUAL nitrogen.

 

[Chris Stock]

whats deep 6?

I looked at one on my last trip. A guy had the watch version as a back up. He used it for a bit as his one and only primary, but wanted AI so bought, you guessed it, a Teric. haha.

 

[ScubaTexas]

We have heard about this previously from @Diving Dubai Here are first, clean air dive NDLs for Suunto Fused RGBM 2, set most aggressively, DSAT, and Buhlmann at a GF high of 95. I have no idea how the Suunto algorithm behaves on repetitive dives. I know from extensive personal experience that DSAT and Buhlmann behave differently, with DSAT becoming relatively somewhat more conservative and Buhlmann becoming relatively somewhat more liberal. Diving Dubai could probably comment on Fused RGBM 2 vs. Buhlman and repetitive dive performance.

View attachment 708437

This is a helpful chart from the above post for comparing first dives under Fused RGBM 2 versus the other mainstream models. The differences are relatively close (closer than I thought they might be). As raised in that post, I too am curious if there is any further comparison information for repetitive dives between the Fused RGBM 2 and Buhlman models. Has anyone found any information or have hands on anecdotal experience providing some insight?

 

[tursiops]

View attachment 725713
This is a helpful chart from the above post for comparing first dives under Fused RGBM 2 versus the other mainstream models. The differences are relatively close (closer than I thought they might be). As raised in that post, I too am curious if there is any further comparison information for repetitive dives between the Fused RGBM 2 and Buhlman models. Has anyone found any information or have hands on anecdotal experience providing some insight?

It gets extremely difficult because there are so many variables. At a minimum, you get a chart like the above for every different Surface Interval (SI). For real dives, you have to also take into account ascent rates, duration and depth of safety stops, and profiles (like square or yo-yo). Not to mention the difference in implementation of the three algorithms above by different dive computer manufacturers, as well as how a manufacturer might implement the algorithm differently in its different models!

One simple comparison is here, but it does not include Buhlmann.

Another, more complicated comparison in 2004 that did include Buhlmann, is here. The results are somewhat disconcerting. 15 computers were tested together in a chamber; up to 3 dives per day for 3 days.
Here are the tested computers:

Dive profiles were characterized as "low risk" or "moderate risk" or "high risk," in terms of how human subjects had previously responded to those same profiles. The moderate and high risk dives were decompression dives. For the low risk NDL dives (first dive deep, second shallow, third moderate), quoting:

Results from the multi-day multi-level “low risk” profiles (Figure 1) ranged from three computers requiring decompression following the first dive of the first day to five computers completing all nine dives within their no-decompression limits (Table 3). The Oceanic and Aeris computers (along with the EDGE) made it through all nine dives without needing to be reset. The Atmos 1 and Versa went into decompression at the end of the first day and cleared out of error mode by the next morning. However, the Smart Pro went into decompression at the end of the first dive and did not clear out of error mode until the morning after the third day of diving. The Archimede did not activate at the start of the first dive and only calculated two days of diving. The Nemesis II was not activated at the start of second dive.​

Here is the summary Table 3:

The Huggins chamber results plus others are summarized in this 2012 article. One punch line is in this graph for the NDL time remaining when arriving at the 15m depth after performing a multilevel dive to 40m. Twenty computers are shown, none of which I believe are still in production.