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Thread: Homebuilt cell checker - Version 3

  1. #1
    Steve Sprague 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster's Avatar
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    rEvo

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    Homebuilt cell checker - Version 3

    When I first became interested in cell checkers I cobbled together one using one of Martin's (TecMe) 3 cell sensor housings for a Dolphin and I used my Shearwater GF to read mVolts. It worked, but then I bought a rEvo, which at the time carried 4 cells. So I built a dedicated Version 2 with a 4 cell capacity. That one had it's own pot, pressure gauge and panel mounted meter. I would write down values and re-enter them into a 4 cell spread sheet to make a cell performance report.

    Then Paul upgraded the rEvo to a 5 cell tray. The primary reason for this was to eliminate the necessity to share cells between displays. I added a 5 cell tray to my rEvo.

    But now I had to run the test procedure twice on my 4 cell checker to test all 5 cells. And I was getting tired of recording the data twice for each test.

    So now, after a long gestation, here is Version 3:
    This nightmare of wiring, plumbing and ancient electronic devices is assembled to provide nearly care free cell checking. It's controlled by an HP-41CX calculator with 2 programs that 1) create data files of cell tests and 2) prints cell reports from data files. Running the cell test program, the calculator coordinates the cell pot, meter and printer to sample up to 6 cells automatically for each pressure level of a cell test. For this program, the only required data entry by the operator are the data file name, the number of cells in the pot, the ID of the cells, and 7 prompted pressures during the test. The cell report program prompts for the file name and 3 variables (Elevation, FO2 of air and FO2 of oxygen used in the test) and then prints a little report for each cell with no other input from the operator.

    I would especially like to thank Curt McNamee for letting me raid his spare parts bins for the cell pot, regulator and various fittings. It saved me a bunch of time sourcing the plumbing. He also let me borrow his work bench and tools to assemble the cell connectors.

    Why did I use an ancient calculator and an antique volt meter instead of modern equipment? Because I already had the stuff, I kinda-sorta know how to program an HP-41 and I am a bit goofy.

    If you are familiar with the HP 41 series calculator you know that one of it's quirks is that, even when it was state of the art, it had a reputation for being rather slow. To isolate the switching between the calculator, the voltmeter and the cells, I used solenoids that are controlled by the calculator. When the program runs you can hear the individual solenoids click on and off while each cell's voltage is being measured. The speed and sound reminds me of Charles Babbage's Difference Engine. Since the cell performance report plots the percent difference from expected mV, I've named the thing "The Difference Engine".
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    Last edited by 4ster; 13th October 2016 at 16:14.

  2. #2
    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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    Meg

    Re: Homebuilt cell checker - Version 3

    Impressive work but you obviously have a lot of free time somehow. We need to go diving more. :)

  3. #3
    Steve Sprague 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster's Avatar
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    rEvo

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    Re: Homebuilt cell checker - Version 3

    The project has been a bit of an obsession. I significantly underestimated the time needed to create both the hardware and the software.

  4. #4
    Reads fine print (mostly) Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather's Avatar
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    Re: Homebuilt cell checker - Version 3

    Quote Originally Posted by 4ster  View Original Post
    The project has been a bit of an obsession. I significantly underestimated the time needed to create both the hardware and the software.
    A quote no doubt repeated by the vast majority of homebuilders!

  5. #5
    RBW Member SimonK is a glorious beacon of light SimonK is a glorious beacon of light SimonK is a glorious beacon of light SimonK is a glorious beacon of light SimonK is a glorious beacon of light SimonK is a glorious beacon of light SimonK is a glorious beacon of light SimonK is a glorious beacon of light SimonK is a glorious beacon of light SimonK is a glorious beacon of light SimonK is a glorious beacon of light SimonK's Avatar
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    Re: Homebuilt cell checker - Version 3

    Quote Originally Posted by Skipbreather  View Original Post
    A quote no doubt repeated by the vast majority of homebuilders!
    and large companies

  6. #6
    RBW Member pegcjs will become famous soon enough pegcjs will become famous soon enough pegcjs will become famous soon enough pegcjs's Avatar
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    Drager Ray

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    Re: Homebuilt cell checker - Version 3

    Great project but pretty much proves that electrochemical sensors are basically a bad technology to start with...

    Sent from my MotoG3 using Tapatalk

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