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Display of SAC Rate

Posted: Sun Jun 21, 2020 5:55 am
by cmcdarris
I really like Dive Log on my iPhone and iPad.

I track my SAC rate and use the Perdix AI dive computer, which tracks my tank starting and ending pressure. I also have my tanks defined in DiveLog in order to have the program calculate my SAC rate. I have noticed that on some dives in DiveLog it shows “Average Consumption Rate” and on other dives it just gives the SAC rate. Why the different display? I cannot find that I am entering the data differently. Last week I made 2 dives and each dive display was different.

(Note: I tried to attach a screenshot to this message showing both displays, but I do not think the forum allows me to submit a photo. If you would like me to email a photo of each screen, let me know.)

Re: Display of SAC Rate

Posted: Sun Jun 21, 2020 8:13 am
by support

The "average consumption rate" is calculated in a couple of situations. The first is if you have multiple tanks/gases used on a dive. The second is any time that Dive Log does not have the information that it needs to calculate a "per tank" air consumption rate. If you have two tanks/gases used on a dive and your computer records the gas switches for each tank (or if you use only a single tank) then Dive Log can calculate the air consumption rate for that tank (it needs the average depth, time and air consumption for the port of the dive used by that tank). In the two tank case that meets this criteria you will see both an average consumption rate and the per tank consumption rate. However, if you define two tanks and you don't record any sort of gas switching during the dive but both tanks have some gas used then we have no way to know how to calculate the per tank rate so we just calculate the "average consumption" (i.e. total gas used over the whole dive using the whole dive average depth).

The Perdix AI presents a few additional challenges as it does not really track "tanks" but just gas switches and transmitters. It does not provide any way to assign a particular transmitter to a particular gas. So we use some heuristics to try to map the gases to transmitters ... but this is not always possible. This might also result in the average consumption rate being calculated but not the per tank rate.

The best way to explain the situation is for you to send me a copy of your logbook via email (support 'at' moremobilesoftware 'dot' com) and I can look at each dive and explain the results. You can generate a copy of your logbook using the Synchronize tab and the tap "Export" and then "Export active logbook". Then choose the location to save the file (iCloud Drive by default). then you can use the Files app on your device to email the logbook or a link to it to our support email address.

I hope that helps.


Re: Display of SAC Rate

Posted: Fri Jul 03, 2020 9:15 am
by cmcdarris
Ah yes. Looking back at the dives in question, it occurs where I carried a pony bottle and did in fact have a transmitter on the bottle, even though the pony was not used. That makes sense. Thank you for the response.