Epee, A-B residual ohmage

Discussion in 'Armory - Q&A' started by jjefferies, Nov 29, 2018.

  1. jjefferies

    jjefferies Podium

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    Checking weapons and I've found a couple in which there is a residual resistance between A-B even when the contact is open. When I say residual I mean 25+ mega ohms when the contact is not depressed. When depressed the resistance is less than 1 ohm. I realize that most scoring machines count 25 mega ohms as being open (well most seem to). But I was wondering if this is a known phenomena that can be corrected. Most of my weapons measue as 0.L when the tip isn't depressed (Fluke 75 multi-meter). Also noted is that with the problem weapons the resistance shows as slowly increasing as though there was a capacitive component to the shorting. I've checked the wires but not found any apparent breaks in the insulation. I'm using super glue if that's of any importance/interest.
    thanks
     
  2. Purple Fencer

    Purple Fencer Podium

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    Are you using your hand to push the tip down?
     
  3. ktinoue3

    ktinoue3 Podium

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    Easy to forget that we are conductive,
     
  4. K O'N

    K O'N Podium

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    He's talking about 25 megaohms when the tip is not pushed down. Presumably he's not using anything to push the tip down when the tip is not pushed down.

    I don't worry about megaohm resistance when the tip is open. Epee wire insulation is very thin, you can scrape it a bit installing the wire, and all modern machines ignore it.
     
  5. nasnem

    nasnem Made the Cut

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    Rule number one in electronics: EVERYTHING is a conductor. No exception!

    Rule number two: All conductors have resistance.

    When you say the contact is "open" you are in fact just measuring a high resistance conductor that has been substituted for the low resistance conductor you were measuring when the circuit was "closed". The high resistance conductor you are measuring is either air, the plastic holding the contacts apart or the insulation(high resistance conductor) between the wires, whichever is the lowest resistance.

    On a side note, since you have two parallel wires separated by an insulator and measuring resistance introduces current you also have capacitance taking place. The longer you hold the meter on, the more you charge the(very inefficient) capacitor.

    Long story short, if you're measuring MegaOhms you have an "open" circuit and a sensitive meter. Nothing to worry about.
     
  6. jjefferies

    jjefferies Podium

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    KO'N is correct. The measurement is made on an open connection and I'm aware of my own conductance. Thus my best guess would be to agree with KO'N and nasmem. But I ran into the first of these when I swapped out a contact spring which wasn't making contact on every press. And while I couldn't go back and check after I had removed the offending contact spring I didn't think I had the problem previously which puzzled me.
     
  7. Mac A. Bee

    Mac A. Bee is a Verified Fencing ExpertMac A. Bee Podium

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    Please don't ever use "ohmage" again. Hurts this EE's eyes.:rolleyes:
     
  8. Goldgar

    Goldgar Podium

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    You just don't want to pay homage to epee.
     
  9. jkormann

    jkormann Podium

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    That hertz.
     
  10. keropie

    keropie Podium

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    I see there is a great deal of resistance to using current terms in this thread.
     
  11. posineg

    posineg DE Bracket

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    I would be shocked by your findings but I am grounded in understanding.
     
  12. jkormann

    jkormann Podium

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    Wow. People are amp'ed up by this topic. Electrifying!
     
  13. Inquartata

    Inquartata Podium

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    Watt just happened?
     
  14. Fairfield_Fencing_Armory

    Fairfield_Fencing_Armory Made the Cut

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    I’m just getting current with this thread... I’ve been out of contact... no wireless service
     
  15. jjefferies

    jjefferies Podium

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    Ooooooh! The sparks are just flying like VET puns passing in the night.
     
  16. Purple Fencer

    Purple Fencer Podium

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    Sorry...I got nuthin’.
     
  17. Inquartata

    Inquartata Podium

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    [​IMG]
     
  18. twisterfencing

    twisterfencing Podium

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    Clean your contacts in the barrel of the blade wire.

    One of two things is happening:

    1. Your contacts are not level or
    2. You have a ton of junk on the contacts and the difference in ohms is one or the other contacts has more junk on it.

    Also: kick your meter to the curb and get a analog meter with a RX1 to help you out, name on it? Who cares. :) OK, I know bunch of you use a digital meter, good for you. I too use a Favero Pro Tester, but check it with one of Dan's boxes.


    Gary Spruill

     
  19. robert

    robert Made the Cut

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    But if you kick your meter to the curb do you pay cash for the new one or charge
     
  20. K O'N

    K O'N Podium

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    You can get a Simpson ohm meter, 372 or similar, on ebay for not much money. Another $15 or so for new leads and you have an analog meter that's better than any cheap meter made today. I wouldn't pick one for a travel meter, they're a bit bulky, but to keep on my bench at the shop they're hard to beat. Rx1 and excellent sensitivity.
     

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