DIY Decompression (by Stuart Morrison)

[jptaylor9]

[chrisch]

The AAB ZHL-16 article was quite good but sadly repeats the incorrect information that the BSAC 88s are a single tissue group table. They are not and are based on three tissue groups.

I have computer too. All this stuff does my head in...

Chris

[Juz]

Jon,

Stuart posts here, so he will no doubt be able to help you with any queries you have from his site.

Juz

[NotDeadYet]

The article was intended as a guide as to how to write deco software, not really as an explanation of the model. I found it quite amazing that people like the makers of Proplanner could charge a small fortune for a few lines of code (I was a bit pissed off too that I'd gone to the expense of doing a trimix course only to get provided with a few vague tables and told to buy Proplanner) and wanted firstly to show it wasn't some kind of black magic going on and secondly to help anyone that wanted to write their own.

XS was originally written because at the time there was only Proplanner really and no real freeware (Zplan had just appeared), and I wasn't paying what Kevin Gurr was asking. It was never a commercial venture, in total I've made about £40 in registration fees in the last seven years, the idea was to make a decent program available to the divers who needed it, not those that could afford it. In fact I gave the code for the algorithm to Phi Le for free so that he could do the same for Decoweenie on the Palm. The article was really to give that help to anyone that needed/wanted it.

You don't know how lucky you are these days!!!

If I can answer any questions then I'll give it a go.

Cheers,

Stuart

[jptaylor9]

[NotDeadYet]

1. AFAIK computers work on sampling the depth every 'x' seconds. They use the Haldane equation, similar to Schreiner but meant for all the time at a constant depth.

2. You can use whatever units you like provided you keep them the same throughout e.g. if you use MSW then you have to convert gas partial pressures to MSW too. Same for bar, psi, fsw, whatever.

3. There is a worked example on this site

Kevin Gurr must be making a fortune, I don't know why. A trimix computer is no more complex than an air one. There is no way I'd pay that. Anyone who can write PICs and knows electronics could produce one (I'd happily sell my ready written C source code! Hint! Hint!). I toyed with the idea of making XS commercial, it even got reviewed in Scuba World and a French mag years ago, but that wasn't the point of the project, in fact it was the complete opposite. Besides it was fun to piss off the makers of Proplanner.

Cheers,

Stuart

[mjgreen]

I'm aware that this thread is kinda old, but...

The problem with proplanner is that its now bloody ancient - I mean DOS is as old me (if not slightly older)! On Windows Vista, I had to use a dos emulator, since dos was removed in 2000/XP (remaining effectively as an emulation layer) and in vista its pretty much gone completely. Once vista becomes the standard operating system on windows machines, proplanner will become effectively obsolete (in the next 2 years or so?)

Of course, I'm ignoring the fact that proplanner will still generate good deco schedules, even if not no longer works on the machine of the person trying to run it. I use it because it generates identical profiles to my vr3 - else I'd use something else. Vplanner is nice, but of course its VPM, and zplan is close but not quite the same, even though its buhlmann.

If Delta P would release the code, I'd happily port it to a windows app (yeah I know, like that's ever going to happen). Would really love to see the features in vplanner, like the ability to generate a pretty excel graph and backup profiles for lost deco gas etc.

And while I'm at it... Hi, I'm new here I'm not a Yorkshire Diver (London), but found the thread whilst looking at the same article referred to & decided to throw my 2p's worth in.

M