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blending calculation tool

Discussion in 'Do It Yourself - DIY' started by ericrd, Aug 9, 2005.

  1. ericrd

    ericrd Instructor, Scuba

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    Hello
    I was fed up of doing some calculations on how much O2 do I have to add on a used tank (with an existing nitrox in it), so I wrote a small java program that runs on my phone.
    It basically prompts for the initial tank pressure, initial FO2, then the desired final tank pressure (usually 3000 psi) and desired final FO2. It then displays how much oxygen needs to be added. It also has a small MOD calculator.

    it runs on any sony ericsson phone, java enabled. I am testing on other phones (motorola, nokia...).

    Anyone that have a sonyEricsson phone and who is interested in testing the software can PM me - you need to have a way to send the program to your phone (bluetooth from your computer, memory stick, IR...). Any feedback welcome.

    eric
     
  2. darylm74

    darylm74 Manta Ray

    # of Dives: 200 - 499
    Location: Pittsburgh PA
    717
    1
    18
    Need to play with it to see if it has java capabilities. If it is Java, it should be portable to any phone running Java since Java is suppose to be platform independent. I would definitely be interested in it.
     
  3. ericrd

    ericrd Instructor, Scuba

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    Hi

    It runs on Java enabled mobile phone - I tested it on Sony Ericsson, Motorola, Panasonic, Nokia. You need to have a way to transfer the app to the handset (via cable, infra red, bluetoooth).

    Instructions are below, program can be downloaded from:
    http://erwanviel.site.voila.fr/blend.zip

    Feedback more than welcome - source available for anyone who wants it (few comments though, but it is really basic stuff).

    eric



    ===============================================
    The version now has 3 functions
    - blending - ie given the current tank content, and the desired mix, computes what quantity of O2 needs to be added.
    - MOD - calculates the MOD for the final mix
    - Top Off

    the main screen contain 4 boxes, that have different use based on the function. Just move the cursor on the text box, hit edit, put the value you want, and hit at the end the more key - three choices should appear - calc, MOD, Top Off.

    Calc.
    This is pretty straightforward, just enter the initial tank pressure and FO2, the final tank pressure and FO2, and hit calc. It is assumed that you take the current tank content, add the O2, and top off with air.
    The result will show how much PSI of O2 you need to add, what will be the tank pressure after you add the O2, the FO2

    after adding the O2, and what happens if your tanks is short filled, by 100,200,300 psi or if you have an extra 100. Apart from the short fill, everything works in PSI or bar, and the unit is not important.

    MOD
    Simply enter on the main screen the final tank FO2 - other paramas are ignored - and hit MOD - you will see the MOD at 1.4 and 1.6, in feet and meters.

    Top-off
    You currently have a tank with initial Tank Pressure and FO2. YOu are topping off with a gas with 'Final FO2' of oxygen, and up to Final tank pressure - you get to see the final FO2 in the mix.

    Calcualtion details
    Java CLDC1.0 does not support floats, so to do these calculations, one has to multiply all figures by a 100, and divide at the very last moment - therefore, the precision is not as good as you would get with float calcs, but are still fairly accurate, at least in PSI - no more than 1-2 psi of max difference.
     
  4. darylm74

    darylm74 Manta Ray

    # of Dives: 200 - 499
    Location: Pittsburgh PA
    717
    1
    18
    Thanks. I am going to play with it tomorrow and see if I can get it on the phone, if not I work for a wireless infrastructure (we own a lot of cellphone towers) company and I'm sure the engineers there will have some ingenious way to do it. If they can't do anything, this would still be valuable on a PDA.

    Thanks again

    Daryl
     
  5. Tamas

    Tamas Solo Diver

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    OH-OH ME-me.....I have been bugging one of my coders to write one for the longest time....but this way I won't have to

    I like.....very simple yet to the point. Can you add a calc for 1.5?

    I also noticed it's off a few PSI in the O2 calc, +4-5%
     
  6. ericrd

    ericrd Instructor, Scuba

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    . calc for 1.5 - I guess you mean MOD ? sure
    . off for o2 calc, +4-5% - can you give an example, so I look at what is happening

    tks for the feedback

    eric
     
  7. Tamas

    Tamas Solo Diver

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    Yes 1.5ATA for MOD, you have 1.3 and 1.6, would be nice (if possible) to have a 1.4 and a 1.5 calc to cover all the bases

    The diff, sure when I use the standard 500psi @ 21% --> 3000psi @ 32% your blender gives me 420 psi to fill then top off with air while the other blender(s) I use say to use 417.7 psi....the higher the O2 % the more the variance.....usually off by +2-3psi.....nothing really major but could be

    other than that, it's cool!
     
  8. ericrd

    ericrd Instructor, Scuba

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    Hi
    MOD is currently working for 1.4 and 1.6 - I'll add 1.5 and 1.3

    Calculations - I took 20.9 and 79.1 as top-up gas.
    The formula is:
    (((Final_Tank_Pressure*Final_FO2-Initial_Tank_Pressure*Initial_FO2)/Delta - TopUp_o2)/TopUp_N2)*Delta

    and it gives 420.354 - when using 21/79, you get to 417.7

    I found the following web site:
    http://www.atomox.com/mix_calc.html

    which shows real gas vs ideal ga. I may implement the calculation.

    Let me know if you think something is wrong here,

    Eric
     
  9. Tamas

    Tamas Solo Diver

    2,211
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    AHA! That would make sense then on the final numbers.

    You mentioned you would share the code? Is that still so?
     
  10. ericrd

    ericrd Instructor, Scuba

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    code: absolutely ! pm your email @ and I'll also send how to set up the dev environment.

    eric
     

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