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Building a Dummy Load Box

Discussion in 'General Electronics Discussion' started by Sublime_Dude, Mar 11, 2014.

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  1. Sublime_Dude

    Sublime_Dude

    2
    0
    Mar 11, 2014
    Hey everyone,

    Just joined up for the purpose on learning on how to build stuff!

    I am wondering if anyone can give me tips on building a Dummy Load Box. I use them at work to simulate Wireline to test oilfield tools. We have one already but need a couple more and I am just seeing how hard or easy it might be to do it myself.

    A typical wireline is about 80 Ohm of resistance with about 3000 meters of single conductor wireline.
    The tools we use need anywhere from 120-200 DCV and reaching only about 80 mA.

    Let me know if you need more info on the wireline and tools!

    The dummy load box looks like it has five 10 Ohm resistors and I think they are capacitors? connected to them as well. They are all on a single board and you connect them through standard UHF connections.

    Im just don't know to much about resistors, I know you can get different wattage in resistors but have no idea what the wattage in a resistor means. Nor I have any idea how a capacitor works in this case. Thanks to all that read, replay, and help me out!
     
  2. davenn

    davenn Moderator

    13,802
    1,941
    Sep 5, 2009
    hi there
    welcome to the forums :)

    show us a sharp and well lit photo or 2

    If you already have one ... why not just copy it ?

    Dave
     
  3. Sublime_Dude

    Sublime_Dude

    2
    0
    Mar 11, 2014
    I can probably get pics tomorrow. If I knew how to copy it I wouldn't be on here asking but thanks.
    Just not sure if what I'm looking at are capacitors next to the resistors or something I'm not familiar with. Also what kind of resistors to get as it's hard to read the stamping on the board.
    Guess wait till tomorrow so I can clear it up.
     
  4. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
    651
    May 8, 2012
    Some of this makes little sense to me.

    (1) If it's only DC that's being carried why does it use UHF connectors, which would also dictate coax cable as the transmission line?

    (2) 80R is an oddball load impedance. 75R is standard for TV, CCTV & data cable. 50R is standard for radio communications.

    (3) 5 * 10R resistors can't = 80R but will = 50R for nominal 52R coax.

    (4) UHF connectors & cables are NOT single conductors.

    (5) Capacitors may be used to compensate for resistor wire lead inductance but this is a guess.

    (6) What are the "Tools" that are being controlled?

    Chris
     
  5. Jibby

    Jibby

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    0
    Sep 12, 2013
    220v X 80mA=17.6 watts. R= V/I=220/.08=2750 ohms. Get from the market any wire wound resistance of 3K ohms, 50 watt
     
  6. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
    651
    May 8, 2012
    Ha, didn't catch this in his first post. I guess wireline resistance means total measured DC resistance of a shorted loop.
    Chris

     
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