MultiDeco v4.19

[MultiDeco]

A new version of MultiDeco / V-Planner is available. This version improves and repairs the Bailout and Maxtime planning, and other minor issues. The PC, Mac, Android and iOS programs are available now, with the Linux one to follow shortly.

Available from: www.multideco.com

 

[Jacob BV]

A new version of MultiDeco / V-Planner is available. This version improves and repairs the Bailout and Maxtime planning, and other minor issues. The PC, Mac, Android and iOS programs are available now, with the Linux one to follow shortly.

Available from: www.multideco.com

is this the 2.22 update for Android. My phone updated on the 02/06/2022

 

[nickbutcher]

Can anyone explain how the gas density is calculated in Multideco?

It gives lower numbers than I derive for a given mix/depth and mine pretty much tally-up exactly with what my Shearwater Petrel reports when I look at a downloaded profile.

For example - 65m using 15/53 diluent at 1.3 set point*, I calculate 5.5g/l and this is what my downloaded profile reports at that depth.

Multideco gives 5.1g/l (in salt water)

FWIW - I'm using densities of:
O2 - 1.428
He - 0.178
N2 - 1.251

* my calculations give a loop mixture of 17.3/51.5/31.1 at 65m

 

[inquis]

You (and Shearwater) are using constituent densities at 0 deg C, but you've configured MultiDeco to use those at 20 deg C. At 0 deg C, MD gives 5.47 g/L.

 

[nickbutcher]

You (and Shearwater) are using constituent densities at 0 deg C, but you've configured MultiDeco to use those at 20 deg C. At 0 deg C, MD gives 5.47 g/L.

Interesting, thanks. I don't know what parameters Shearwater use but the dive in question was done in 10c water.

Where can I find the option to set the temperature? I'm not seeing anything on the config screen.

 

[inquis]

Where can I find the option to set the temperature?

Tools/Gas Density

 

[nickbutcher]

Tools/Gas Density

Not in the Mac Desktop version:

I'm referring to the gas density displayed in the Dive Plan:

 

[inquis]

Sorry, I'm afraid I can't speak to the Mac version. (I was looking at the Android version.)

 

[inquis]

If you can't convince MD to give you densities at 0 deg C, you could use the 20 deg C equivalent of your desired limit by multiplying by 0.932. For example, if your desire is to stay under 5.2 g/l (at 0C), you would want to stay under 4.85 g/l (in MD at 20C).

 

[nickbutcher]

If you can't convince MD to give you densities at 0 deg C, you could use the 20 deg C equivalent of your desired limit by multiplying by 0.932. For example, if your desire is to stay under 5.2 g/l (at 0C), you would want to stay under 4.85 g/l (in MD at 20C).

Thanks @inquis

It's not a showstopper. I've written a spreadsheet to calculate this stuff myself and seldom use Multideco any more. I was just curious about the number being shown in the dive plan but couldn't find an explanation for its derivation.

My calculations are just using ideal gas laws but I assume that your figure of .932 is just an application of Charles's Law (273.15/293.15)?

Maybe I'll add a fudge factor for this to my own spreadsheet. I'm rarely lucky enough to dive in water of 20c but neither do I dive in 0c water (usually between 7 and 13 in Scapa Flow) so should correct for that if those densities I quoted above are at 0c (I just grabbed them from the web).