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r we able to male precise 1ohm resistance

Discussion in 'Electronic Design' started by [email protected], Apr 18, 2007.

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  1. Guest

    how can we make it if we wann i realy wann to konow abt it
     
  2. Uwe Bonnes

    Uwe Bonnes Guest

    If you can't write a sensible question, I guess the same applies for more
    things :-(
     
  3. John Fields

    John Fields Guest

     
  4. MassiveProng

    MassiveProng Guest

    He must be all doped up. Still, he seems smarter than some of the
    fare that has passed through the group in the last month.
     
  5. default

    default Guest

    Mr. Cool Groper

    Learn to type real words, get a real news reader, post to a basic
    group if you have a basic question, learn how Usenet works and follow
    the conventions.

    DITCH GOOGLE Google is not your friend; or ours.

    Sorry
    That's probably way over your head. Try this:

    Lern t ype wrds get a nwsrdr post t a basik grp w/ basik ques lern
    usenet don use ggle
     
  6. Guest

    I hate to admit it, but John Fields is right, as far as he goes.

    If you want a precise and stable 1.00 ohm reistance, it helps to use
    manganin or constantan wire. Both alloys have a very low temperature
    coefficient of resistance at room temperature

    http://www.goodfellow.com/csp/active/static/A/Manganin_-_Resistance_Alloy.HTML

    http://en.wikipedia.org/wiki/Constantan

    http://www.goodfellow.com/csp/active/STATIC/A/Constantan_-_Resistance_Alloy.HTML

    For low resistance resistors, it is a good idea to use the wire to
    make a Kelvin four-terminal resistor - the current through the
    resistor flows through two of the leads, and you measure the voltage
    drop across the 1.00 ohm length of wire through two other leads. See
    page 5 of the appication note below

    http://www.welwyn-tt.com/pdf/application_notes/Current-Sense_AN.pdf
     
  7. Is there absolutely no thread or subject you wont try to hijack with
    your abuse and nonsense?

    X-Complaints-To:
     
  8. Tom Bruhns

    Tom Bruhns Guest

    That depends on what you have to start with. Can you accurately
    measure voltage and current? Do you have an accurately-known
    resistance of some other value already? Do you have a way to control
    the temperature of the resistor after you make it, so that thermal
    drifts and thermal emfs won't destroy its accuracy? What materials do
    you have to make it from? Just how accurate do you want it?

    The people who DO know how to make very stable, accurate resistors
    understand not only the theory but the art: they understand how to
    process the materials so that, for example, stresses don't destroy the
    accuracy.

    Do a Google search for things like "history of resistance standards"
    and you'll find some info on it. The paper at
    http://nvl.nist.gov/pub/nistpubs/sp958-lide/html/063-065.html about
    resistance standards is pretty interesting; the NBS (now NIST)
    resistance standard from about 1931 up until 1990 was a set of 1-ohm
    resistors that are still in use today as transfer standards.

    Cheers,
    Tom
     
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