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1 megohm resistors that only measure 400-500K ohm- should they be replaced ?

Discussion in 'Electronic Design' started by DeserTBob's Futile Efforts, Sep 23, 2007.

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  1. how critical is it, that resistors of 1 megohm value markings, measure
    that value

    I have an old R2R set that all the resistors measure OK in, except for
    (2) of the 1M-ohm values

    can a small Fluke digital multimeter measure that high a resistance
    accurately, with the 9v battery inside ?
     
  2. redbelly

    redbelly Guest

    It depends on the application, but your reading could easily be off if
    you're measuring the resistors without removing them from the
    circuit. The circuit could have a parallel resistance that brings the
    measured value down lower.

    Most DVM's worth anything can measure over 1M-ohm, and most Fluke
    DVM's are worth something. And if it couldn't measure 1M, the display
    would indicate an open circuit, rather than report a value that is
    incorrect.

    You would need to remove the resistors from the circuit in order to
    get a meaningful measurement. And, for a dollar you could get some 1M
    resistors from Radio Shack (if you're in the USA) if it turns out you
    need to replace them.

    Regards,

    Mark

    p.s. this would have been more appropriate for sci.electronics.basics
     
  3. John Larkin

    John Larkin Guest

    If you mean an R:2R DAC network, the LSB-end resistors are sometimes
    half the normal values.

    John
     
  4. JeffM

    JeffM Guest

  5. Yes - no problem.

    However, when measuring high value resistors be sure that your body is
    not part of the circuit being measured. If you use your fingers to
    hold the resistor leads against the probe tips, your body resistance
    will be enough to bring the indicated value down from 1 meg to 500 K
    or less.

    If you are measuring the component while it is soldered into a board,
    there maybe other components in parallel with it that cause a
    lower-than-expected reading.


    --
    Peter Bennett, VE7CEI
    peterbb4 (at) interchange.ubc.ca
    new newsgroup users info : http://vancouver-webpages.com/nnq
    GPS and NMEA info: http://vancouver-webpages.com/peter
    Vancouver Power Squadron: http://vancouver.powersquadron.ca
     

  6. Good call. Even "coffee breath" is enough to alter high value
    resistors. Especially at higher voltage excitations.
     
  7. DeserTBoB

    DeserTBoB Guest

    Don't help this eBay con artist and spammer, Charles M. Nudo, Jr., of
    Drums, PA, "66-catalina" on eBay. He is one of the worst eBay
    spammers ever to hit Usenet via Google Groups, which has already
    banned 28 of his accounts for spamming, threats of violence, divulging
    personal information and the like.

    Take his spam-gram, copy including header, and forward to his ISP,
    Frontier.net, adding "SPAM FROM YOUR SUBSCRIBER" to the fwd title, to:



    Also, cc:



    So far, 28 of his Google Groups accounts, as well as two of his AIOE
    accounts, have been terminated for spam. Let's clean him out for
    good!
     
  8. Robert Baer

    Robert Baer Guest

    Up to 100 Megs, with 1% (as a guess without knowing model and/or
    specs) accuracy.
    Are you sure that other resistors are *not* in parallel with the
    "suspect" resistors?
     
  9. JeffM

    JeffM Guest

    (was: 1 megohm resistors that only measure 400-500K ohm-
    should they be replaced ?)

    Seems like you're all mouth and no action.

    ....or are you just incompetent?
    There a lot of people that don't want to see spam-related stuff.
    THEY configure their newsreaders as such
    and I make it easy for them to weed out this stuff.

    Too bad you only have half a brain.
     

  10. good post- DeserTBob has established himself as the urinal piss-bubble
    foam of Usenet, killfile is the remedy for him
     
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