Logbook question

[highlandfarmwv]

When filling out the PADI logbook at the end of a dive, using computer info, should you use the deepest depth or the average depth. Looking at how the computer derives the average depth, it is not just "half the deepest depth", it is using the amount of time at all depths, averaged.

When using the deepest depth for the calculations, it is a lot farther deviation between tables and computer. But my teacher said the deepest must be used. Why? Thanks.

 

[ChillyWaters]

When filling out the PADI logbook at the end of a dive, using computer info, should you use the deepest depth or the average depth. Looking at how the computer derives the average depth, it is not just "half the deepest depth", it is using the amount of time at all depths, averaged.

When using the deepest depth for the calculations, it is a lot farther deviation between tables and computer. But my teacher said the deepest must be used. Why? Thanks.

For your own information, put down both the deepest and average. If you want to use the tables as a back-up, then calculate using the deepest depth.

Using the average depth will have you in a chamber before you know it.

- ChillyWaters

 

[SparticleBrane]

I don't quite understand why "using the average depth will have you in a chamber before you know it". I am of the understanding that the average depth is definitely a better way to track the amount of nitrogen you've ingassed rather than the deepest.

 

[ChillyWaters]

I don't quite understand why "using the average depth will have you in a chamber before you know it". I am of the understanding that the average depth is definitely a better way to track the amount of nitrogen you've ingassed rather than the deepest.

I guess if you're using the computer FOR your dive, and then use the average on the table, you'll probably come out with a group that is LOWER than what you actually are. Thus being conservative, eh?

Of course, it might be good to know how the computer is calculating the average depth before you attempt this.

- ChillyWaters

 

[Ed Palma]

I agree with ChillyWaters. It is the deepest dive that should be recorded. When manipulating data, the most conservative values should be used in order to maintain a wide margin of safety. If we didn't have computers, and tried to extrapolate our data (average depth and total bottom time) to get a rough estimate of how long we could stay down, we run the risk of surpassing safe limits.

 

[tracy_from_oz]

The deepest depth as Doc Ed has said. It gives the most conservative margin for safe limits.

 

[El Orans]

The deepest depth as Doc Ed has said. It gives the most conservative margin for safe limits.

I agree completely.

 

[Trisha]

Let's say you wind up in the hospital the day after your dive with symptoms similar to those of decompression sickness. You will want to give your dive insurance rep (you do have DAN or PADI or a similar insurance, right?) those maximum depth and time numbers. Lung overexpansion injuries and running out of air are immediate worries, but DCS can appear 12 hours after your last dive (looking in my SSI book here.)

 

[SoCalAngel]

When filling out the PADI logbook at the end of a dive, using computer info, should you use the deepest depth or the average depth. Looking at how the computer derives the average depth, it is not just "half the deepest depth", it is using the amount of time at all depths, averaged.

When using the deepest depth for the calculations, it is a lot farther deviation between tables and computer. But my teacher said the deepest must be used. Why? Thanks.

I put both deepest and average in my log. If you truely want to calculate your pressure group the true PADI way, then you need to go by deepest depth with the RDP OR you can use a wheel, if you know how long you stayed at what depths - especially good if you were doing a pinnacle, wall or shore dive. The wheel will give you a closer pressure group to the computer's calculations, depending on its conservation settings.

 

[BarryNL]

I don't quite understand why "using the average depth will have you in a chamber before you know it". I am of the understanding that the average depth is definitely a better way to track the amount of nitrogen you've ingassed rather than the deepest.

Well, the tables are meant to be used based on maximum depth and that's how the no-stop times and nitrogen groups have been calculated. That's why you use them that way.