testing resisters

Discussion in 'General Electronics Chat' started by lorusso, Nov 3, 2004.

  1. lorusso

    Thread Starter New Member

    Nov 3, 2004
    how do you test the resisters in a circuit and what is used
  2. beenthere

    Retired Moderator

    Apr 20, 2004

    You test resistors with an ohmmeter. Reading in circuit can give questionable results, as ther can be non-obvious conduction paths which will result in low readings. Always make sure the circuit is deenergized first. Having devices like ez-hooks rather than the normal probes makes life easier.

    Learn the color code, too. It helps if you know in advance what the resistance should be.
  3. Steel


    Oct 27, 2004
    You will have to remove the resistor from the circuit. The ohm meter will also pick up other elements in the circuit.

    If reading the color codes isn't good enough, then De-solder the resistor, remove it, and check the resistance with an ohmmeter.
  4. sampinoy

    Active Member

    Sep 24, 2004

    is there a way to check resistors without removing it from the board? :)
  5. cyberhehe

    Well-Known Member

    Oct 6, 2004

    Yes there is, just pull out one leg then you dont have to remove it completely from the board :D haha, just kiddin. But you can do it this way for axial components. With chip resistors in surface mount implementation, you cnat do it this way :(

    It will be very difficult to check the actual resistance of a resistor in circuit, specially if you dont know how it was connected within the schematic of the board. And even if you have schematic, it's difficult to do, i.e. you have a resistor to test that based on the schematic it is parallel with another resistor, though you may be able to analyze and get a calculated estimate on how much resistance you would expect to read including the surrounding component that may influence the reading.

    Also another way you can do when doing some test in circuit, is to conduct voltage or current measurements. For transistor based circuits, voltage reading is very effective specially when checking the bias voltages from point to point. In this way, you can avoid doing resistance check by having some conclusions based on your voltage readings.