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Shearwater Teric wish list
- Thread starter Nick Ruberg
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Jay
Need to dive more!
I'm wondering why SAC is sometimes muddled. Is it simply an error or is there some logic or reason behind the (what I also see as) the incorrect version?
Computer-wise, are SW and Suunto are on the same page. Mares avoid the terms in their Genius manual but permits Gas Consumption to be displayed either in pressure or volume per minute. Oceanic and Ratio appear not to calc either (ref OCi manual, iX3M and transmitter).
Mike1967
Contributor
LOTS of misuse! Some is listed below.
DiveLogs: Surface Air Consumption (SAC) calculations for Scuba divers uses vol/min.
So does Subsurface: "The units for SAC is liters/min or cubic ft/min." Subsurface Version 4 User Manual | Subsurface
Air Management: More Than an Occasional Glance at an SPG! - SDI | TDI | ERDI | PFI uses vol/mion for SAC. "For the record, an average baseline SAC for a relatively experienced diver is around 14-16 litres, or about 0.5 to 0.6 cubic feet, a minute,"
NACD uses vol/min for SAC. See their Cavern and Cave Manual.
PADI (Tec manual) uses SAC in vol/min but says it can also be pressure/min.
NOAA says SAC is pressure/min.
US Navy Dive Manual only uses RMV (vol/min), never mentions SAC.
See also https://www.scubaboard.com/community/threads/sac-vs-rmv-revisited.577745
Jay
Need to dive more!
Mike1967
Contributor
Mike1967
Contributor
sharkguy05
Registered
I would agree that is how there teric operates, which I do not agree with and is why I suggested to shearwater a RMV cal should be an option vs SAC. Maybe I did not make my point clear. If I make a plan for my dive based on the volume of gas I have this will be my limiting factor. Yes the GTR calc is based on the drop over time, but I would like it or another setting to account for the volume of gas i have left which is going to vary from tank to tank based on it operating specs. All I am saying is that with a RMV readout it will limit the math I have to do under water and a GTR that does account for the volume of gas I have makes for simple math. Sure if your at 100ft and you stay there and your sac is 30psi/min and you have 300psi in your tank and the your reserve is 0psi then you have 10 minutes at that depth which is how the teric operates. A computer to that has something similar to the features I would like to see on the teric for gas calculations is the Atomic cobalt. Yes their GTR is calculated by pressure drop over time also.
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Hi @sharkguy05
Perhaps we are talking about the same thing, but, at the very least, we are not communicating well
All air time remaining/gas time remaining calculations are done the same way, by pressure drop over time, extrapolated to the set end pressure. Some calculations include stops (safety or deco) and some assume direct ascent to the surface.. ATR/GTR is cylinder size and operating pressure independent. Assuming the calculation is accurate, ATR/GTR will always give you an estimate of the dive time remaining until surfacing will land you near your end pressure. I have been diving an Oceanic AI computer for about 18 years/1850 dives and can confidently say that the ATR calculation for no stop and light deco dives is quite accurate. I have also been diving a Teric for about 9 months/a little over 100 dives and am not yet able to say the calculation is as accurate as I am used to.
SAC (pressure/time) and RMV (volume/time) are both normalized to the surface, 1 atm. SAC is cylinder dependent, while RMV is not. Personally, I don't find the instantaneous SAC or RMV, while diving, of utility for calculating remaining dive time. I used the SAC calculation on my Teric for a while. It was interesting to see some of the gas use increases with exertion but, overall, I did not find it of utility, and dropped it from my screen. If this calculation was RMV, my comment would be the same.
On the other hand, RMV is quite useful for calculating gas requirements for a dive with a known profile. Due to my experience with my Oceanic computers, I also have my average RMV from those 1850 dives and frequently use it for calculating gas needs. On board, the Teric gives me SAC for the dive from the log. It is very easy to convert this to RMV by using the cylinder characteristics. For example, SAC in psi/min x tank in cubic feet/psi = RMV in cu ft/min. Some have argued that the Teric calculate RMV directly, instead of, or in addition to, SAC. That would require that one enter the cylinder size and operating pressure for each dive or any time it changes. Shearwater decided that this was not practical for many divers.
I apologize to non-Teric users and my metric colleagues for my examples
I hope this makes sense.
Perhaps we are talking about the same thing, but, at the very least, we are not communicating well
All air time remaining/gas time remaining calculations are done the same way, by pressure drop over time, extrapolated to the set end pressure. Some calculations include stops (safety or deco) and some assume direct ascent to the surface.. ATR/GTR is cylinder size and operating pressure independent. Assuming the calculation is accurate, ATR/GTR will always give you an estimate of the dive time remaining until surfacing will land you near your end pressure. I have been diving an Oceanic AI computer for about 18 years/1850 dives and can confidently say that the ATR calculation for no stop and light deco dives is quite accurate. I have also been diving a Teric for about 9 months/a little over 100 dives and am not yet able to say the calculation is as accurate as I am used to.
SAC (pressure/time) and RMV (volume/time) are both normalized to the surface, 1 atm. SAC is cylinder dependent, while RMV is not. Personally, I don't find the instantaneous SAC or RMV, while diving, of utility for calculating remaining dive time. I used the SAC calculation on my Teric for a while. It was interesting to see some of the gas use increases with exertion but, overall, I did not find it of utility, and dropped it from my screen. If this calculation was RMV, my comment would be the same.
On the other hand, RMV is quite useful for calculating gas requirements for a dive with a known profile. Due to my experience with my Oceanic computers, I also have my average RMV from those 1850 dives and frequently use it for calculating gas needs. On board, the Teric gives me SAC for the dive from the log. It is very easy to convert this to RMV by using the cylinder characteristics. For example, SAC in psi/min x tank in cubic feet/psi = RMV in cu ft/min. Some have argued that the Teric calculate RMV directly, instead of, or in addition to, SAC. That would require that one enter the cylinder size and operating pressure for each dive or any time it changes. Shearwater decided that this was not practical for many divers.
I apologize to non-Teric users and my metric colleagues for my examples
I hope this makes sense.
leman
Registered
Haven’t read through all the comments, but I wish the compass was accessible in watch mode as well as stopwatch/timer. Would help when running a tender line.
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