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Shifty Capacitors

Discussion in 'Electronic Basics' started by Ron Hubbard, Aug 9, 2003.

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  1. Ron Hubbard

    Ron Hubbard Guest

    In checking out some surplus caps using the capacitance
    function of my wavetek multimeter, there were a few that
    flickered between values. For most occasions I wouldn't worry
    about it, but I have a project requiring matched capacitors.

    My question, if the value is flickering between say 0.334uF
    and 0.335 uF, how do I know if the cap is the higher or lower
    value?

    Thanks
     
  2. Bob Masta

    Bob Masta Guest

    It's probably around 0.3345 uF and the meter is just doing
    the best it can.

    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    Shareware from Interstellar Research
    www.daqarta.com
     
  3. Wade Hassler

    Wade Hassler Guest

    You don't know which value it is. The two are within 1% of each other
    and that's a good enough definition of 'matched' for most projects.
    Forge ahead, and make enough money to get a .1% meter!
    Wade H
     
  4. DarkMatter

    DarkMatter Guest


    You give a *cheap* handheld way to much credit in the realm of
    capacitance or inductance testing. Even an *expensive* handheld is no
    substitute for a good RLC bridge for the level of resolve he is
    apparently after.
     
  5. John Larkin

    John Larkin Guest

    Almost everyone manages to say something intelligent on occasion.

    *Almost* everyone.

    John
     
  6. Roy McCammon

    Roy McCammon Guest

    .----R1----+-----C1------.
    | | |
    | | |
    Signal Source -----+ meter +--- gnd
    | | |
    | | |
    '----R2----+-----C2------'


    Get matched resisters R1 = R2.
    Choose R1 close to the reactance of C1 at the frequency of interest.

    Match C1 and C2 by minimizing meter reading.
    You should be able to match the caps to almost
    the same matching as the resisters.
     
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