Average Gas Consumption
- Thread starter scubadada
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Not sure why you would want surface consumption rate during a dive, other than a measure of relative exertion. Seems to me current consumption rate would be more useful since you would need to multiply the SAC by your relative depth to get current usage.
Belzelbub
Contributor
SAC during the dive can be useful if you use the same tank, a higher than normal SAC could indicate either higher than normal exertion. Just using actual consumption wouldn't be as useful in my opinion. For current consumption, the benefit would be how much time is left. This is available in the GTR field. That, I find to be more useful than how much PSI is consumed.
OP
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I have been diving an Oceanic VT3 since 2010, the air time remaining is quite accurate and includes your safety stop or deco stops(s)
I added a Shearwater Teric on the same transmitter in 2019. The gas time remaining does not seem as accurate to me, and is generally shorter than on the VT3, especially at the beginning of the dive. The ATR and GTR are generally very close toward the end of the dive. The Teric does not include the gas for the safety stop but it can be added when designating the reserve pressure. Here, I have added the pressure I would generally use for a 3 min SS at 15 feet
I had intended on documenting the differences in ATR and GTR, but lost interest, perhaps someday. On the Teric, the GTR is not displayed once you enter deco.
I almost always dive rental AL80s and know my gas consumption very well. As per @Belzelbub and @tursiops I only use SAC to estimate my current level of exertion, or lack thereof. My average RMV is 0.36 cu ft/min or 14 psi/min with an AL80. It is easy to compare my current SAC to that value.
Most of my diving is no stop, with about 5% light deco. I have chosen to format my home screen as below. I use standard screen in rec mode. I placed T1 pressure in the right side of the 2nd row as I have little use for TTS. I formatted the info row as shown. I use SurfGF on my safety stop or deco stop to give me my desired surfacing GF. I only occasionally glance at GTR or SAC. I like the floating north pointer as that is all I generally need for most of my diving.
When I download my VT3, it gives me both SAC and RMV. The Teric gives me SAC, you must multiply by the tank factor to obtain RMV
I added a Shearwater Teric on the same transmitter in 2019. The gas time remaining does not seem as accurate to me, and is generally shorter than on the VT3, especially at the beginning of the dive. The ATR and GTR are generally very close toward the end of the dive. The Teric does not include the gas for the safety stop but it can be added when designating the reserve pressure. Here, I have added the pressure I would generally use for a 3 min SS at 15 feet
I had intended on documenting the differences in ATR and GTR, but lost interest, perhaps someday. On the Teric, the GTR is not displayed once you enter deco.
I almost always dive rental AL80s and know my gas consumption very well. As per @Belzelbub and @tursiops I only use SAC to estimate my current level of exertion, or lack thereof. My average RMV is 0.36 cu ft/min or 14 psi/min with an AL80. It is easy to compare my current SAC to that value.
Most of my diving is no stop, with about 5% light deco. I have chosen to format my home screen as below. I use standard screen in rec mode. I placed T1 pressure in the right side of the 2nd row as I have little use for TTS. I formatted the info row as shown. I use SurfGF on my safety stop or deco stop to give me my desired surfacing GF. I only occasionally glance at GTR or SAC. I like the floating north pointer as that is all I generally need for most of my diving.
When I download my VT3, it gives me both SAC and RMV. The Teric gives me SAC, you must multiply by the tank factor to obtain RMV
Belzelbub
Contributor
To be fair, that's really a limitation of the dive log software you are using rather than the computer. Neither has an input on the computer for tank size. IIRC, you are using Diverlog+ for your VT3 and Shearwater Cloud for the Teric. I'm not using Diverlog+ anymore and use Shearwater Cloud primarily for updating firmware. Subsurface and many other dive logs will give you RMV as soon as you tell it what tank you are using. No math required, at least for you.
OP
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Correct. I use an even older dive log for my Oceanic VT3, OceanLog. It has a dropdown list for all cylinders I use
The Shearwater Cloud does not currently have the option of entering the cylinder data to calculate RMV from SAC. You must calculate that yourself.
Belzelbub
Contributor
That's right. When I got my VT4.1, I was directed to DiverLog+, but I also received a copy of OceanLog. Never used that as I didn't have a Windows PC.
Subsurface functions the same way. You select the cylinder you use, and RMV is automatically calculated. There is even an option to set a default cylinder, so if you normally use one, then that will be populated for new logs unless you change it. It also lets you graphically display your RMV with a Box and whiskers plot so you can see the range and trend over time.
Shearwater Cloud does give you the option to populate cylinder information, but it doesn't really do anything other than record the size of the cylinder.
OP
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Hi @Belzelbub
OceanLog also has a default cylinder that is used unless you designate another.
I have submitted addition requests to the Shearwater Cloud on several occasions, cylinder designation and auto-calculate RMV is one of them. I would also like to see SurfGF on the dive graph, so that it can be seen at any point during the dive.
There was an example of the Subsurface RMV graphing in post #354 Average Gas Consumption This is presented by year with median, surrounding 2nd and 3rd quartiles, and the the full range. It looks like it can be displayed in different ways. Could you post an example of what yours looks like?
As I don't have an auto-graphing option, I have tracked my RMVs since 2010 with averages and std dev. I have this by year and overall. My RMV has decreased just a little, as has the variation. I did not start tracking my RMV until I had about 450 dives.
I compared the 6 1/2 years from 2010-2016 to the nealy 6 years from 2017 to date
There is a highly statistically significant difference in my mean RMV between the 2 periods, though this is of little to no practical importance. The standard deviation (variation) also decreased.
OceanLog also has a default cylinder that is used unless you designate another.
I have submitted addition requests to the Shearwater Cloud on several occasions, cylinder designation and auto-calculate RMV is one of them. I would also like to see SurfGF on the dive graph, so that it can be seen at any point during the dive.
There was an example of the Subsurface RMV graphing in post #354 Average Gas Consumption This is presented by year with median, surrounding 2nd and 3rd quartiles, and the the full range. It looks like it can be displayed in different ways. Could you post an example of what yours looks like?
As I don't have an auto-graphing option, I have tracked my RMVs since 2010 with averages and std dev. I have this by year and overall. My RMV has decreased just a little, as has the variation. I did not start tracking my RMV until I had about 450 dives.
I compared the 6 1/2 years from 2010-2016 to the nealy 6 years from 2017 to date
There is a highly statistically significant difference in my mean RMV between the 2 periods, though this is of little to no practical importance. The standard deviation (variation) also decreased.
