Resistor measurement

Discussion in 'General Electronics Chat' started by Webby, Aug 11, 2008.

  1. Webby

    Thread Starter Active Member

    Jun 15, 2008
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    0
    Hi, in a simple circuit with say three resistors wired in series (10ohm, 5ohm and a 15ohm resistor) if I open the circuit and attach my multimeter one end of the circuit to the other end should I beable to measure total resistance =30ohms?
     
  2. Audiofilo

    Member

    Jul 15, 2008
    13
    0
    For resistance measurements you need close circuit, the multimeter send a current and then calculate resistance across voltage measured in.

    So, for get 30 ohms, from your circuit, you need measures in the ends.
    If you open, (and the ends are free) you can not measures anything (the multimeter will display OR, Over Range, say infinite resistance).

    Do not confuse resistance with impedance. The first is for DC, and second for AC, sometimes they are equal, but it is other theme.
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    If by opening the circuit you mean arranging it so only the resistors are being measured (no parallel paths), then you should be able to use a multimeter and see 30 ohms total resistance.
     
  4. Webby

    Thread Starter Active Member

    Jun 15, 2008
    66
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    Hi thats what I thought....if its a series circuit with no parallel paths. Thanks for that info. Now im confused what "Audiofilo" meant?
     
  5. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    I think that Audiofilo said thay you would need to create a "closed" circuit formed by the three resistors in series and the multimeter. That is a way to see things, and technically it is a closed circuit. Of course, the resistance of a resistor or association is always measured with at least one end of the resistor or association free, so eventual parallel components (parallel to the resistor or association, so to speak) that may exist in your circuit won't affect your measurement.
     
  6. silvrstring

    Active Member

    Mar 27, 2008
    159
    0
    Webby, you are correct.
     
  7. Webby

    Thread Starter Active Member

    Jun 15, 2008
    66
    0
    Hi all, thanks for your input, with a closed series circuit and using my meter across the circuit (parralel) would I be able to read a resistor value or only total resistor value being as there still connected to the rest of the circuit.
     
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