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Thread: Divesoft Analyzer for continuous mixing

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    Roland Somodi rolanddiver is a glorious beacon of light rolanddiver is a glorious beacon of light rolanddiver is a glorious beacon of light rolanddiver is a glorious beacon of light rolanddiver is a glorious beacon of light rolanddiver is a glorious beacon of light rolanddiver is a glorious beacon of light rolanddiver is a glorious beacon of light rolanddiver is a glorious beacon of light rolanddiver is a glorious beacon of light rolanddiver is a glorious beacon of light rolanddiver's Avatar
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    Divesoft Analyzer for continuous mixing

    Gentlemen,

    I have a lovely divesoft trimix analyzer that is capable of supporting continuous mixing as per the manual. Since the oxygen sensor is located inside the housing of the analyzer and the machine requires 0.2 liter per minute flow for an accurate reading I don't really see the way of connecting it to a nitrox stick. Since in the compressor intake the pressure is always less than the ambient pressure how do you push the gas thru the analyzer to achieve the desired flow rate? If you use the flow limiter supplied with it, than you can only do the measurement downstream of the compressor, which is not an ideal thing as you want to see what is being sucked into the compressor (O2 spikes, etc) and not what is being pump out of it. Obviously one could take the analyzer apart and connect an auxiliary O2 sensor to the PCB with a longer cable and the problem is solved, but I'm sure it wasn't intended/designed to be used that way. Any ideas are more than welcome. thanks
    Last edited by rolanddiver; 5th January 2018 at 08:53.

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    Re: Divesoft Analyzer for continuous mixing

    I don't know if this will be the same for you, but here's what I did: I picked up a mini sampling air pump (about $20 on fleabay), got a small plastic electronics project enclosure, a switch and power light, and a 9v battery. I built a little aux pump and I installed it between my nitrox stick and analyzer, and it gives me a constant, accurate feed for analyzer. I spent about $35 on the whole thing. It works like a charm, and super easy to do.

    Hope this helps.

    FD

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    RBW Member jeff h will become famous soon enough jeff h will become famous soon enough jeff h will become famous soon enough jeff h will become famous soon enough jeff h's Avatar
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    Re: Divesoft Analyzer for continuous mixing

    I wonder if you could just T in two barbs that are a couple of feet apart into the intake after the mixing stick. Then run tubing to the analyzer that would be in parallel with the intake. There might be enough of a pressure differential to pull it through the system.

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    RBW Member rjack will become famous soon enough rjack will become famous soon enough rjack will become famous soon enough rjack's Avatar
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    Re: Divesoft Analyzer for continuous mixing

    Quote Originally Posted by jeff h  View Original Post
    I wonder if you could just T in two barbs that are a couple of feet apart into the intake after the mixing stick. Then run tubing to the analyzer that would be in parallel with the intake. There might be enough of a pressure differential to pull it through the system.
    you need a sampling pump, here in the USA Hargraves makes them (now part of the huge company parker). They come in 9V, 12V plus some other versions. Most in the 2L flow range. I have one but haven't used it in years because pumping 100% into the compressor intake is so much easier than juggling o2 and helium inputs.

    https://www.hargravesfluidics.com/

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    Re: Divesoft Analyzer for continuous mixing

    I was thinking about some sort of small pump, but didn't know they actually exist. Thanks a lot to all for the great ideas. Going to ebay to buy one right now.Much appreciated.

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    Re: Divesoft Analyzer for continuous mixing

    Quote Originally Posted by rjack  View Original Post
    you need a sampling pump,...
    Yes, I've seen this done before with simple aquarium pumps. I bet you could get flow without a pump though.

    Quote Originally Posted by rjack  View Original Post
    ...I have one but haven't used it in years because pumping 100% into the compressor intake is so much easier than juggling o2 and helium inputs...
    100% of what??

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    Re: Divesoft Analyzer for continuous mixing

    Sampling pump is tiny, about the size of a pecan. When I get home tomorrow I'll take a few pics of my set up and post so you can see how mine is done.

    FD

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    RBW Member rjack will become famous soon enough rjack will become famous soon enough rjack will become famous soon enough rjack's Avatar
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    Re: Divesoft Analyzer for continuous mixing

    Quote Originally Posted by jeff h  View Original Post
    Yes, I've seen this done before with simple aquarium pumps. I bet you could get flow without a pump though.



    100% of what??

    You can't get flow to go from the stick into an analyzer, the stick is under negative pressure. By installing an analyzer without a pump you are essentially creating a leak in your stick, ambient air is going to preferentially flow backwards through your analyzer.

    oil lubed compressors can handle 100% helium at modest pressures quite easily. I quit continuous mixing trimix 6+ years ago and just partial pressure blend using the compressor to scavenge helium and put it into a bank cylinder. I wouldn't do it more than about 30-40 mins or the oil starts to get a bit foamy. Piston blow-by has always been modest for me below about 2200-2300psi. While I don't have an objective measure, wear and tear from modest pressures of 100% helium seems less or no greater than pumping higher pressures of trimix. At least using piston blow by as a metric, pumping 100% helium then topping with a helium free gas has ALOT less blowby than trying to pump 15/55 at 3000+ psi.

    I top off my 100% in the bank cylinder with 32% to make 18/45, 15/55 or 12/65.

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    Re: Divesoft Analyzer for continuous mixing

    Quote Originally Posted by rjack  View Original Post
    You can't get flow to go from the stick into an analyzer, the stick is under negative pressure. By installing an analyzer without a pump you are essentially creating a leak in your stick, ambient air is going to preferentially flow backwards through your analyzer.
    You didn't follow what I was saying at all. Put "two" barbs in the system, one close to the compressor intake and one upstream and have a tube run in parallel to the intake. Then put the analyzer in this tube. If they are far enough apart there definitely will be a pressure differential and some flow.

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    Re: Divesoft Analyzer for continuous mixing

    This might help

    Mix_Sampling.jpg

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