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More beginner questions (digital multimeter)

Discussion in 'Electronic Basics' started by Lucretia MacEvil, Mar 12, 2007.

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  1. Does your DMM get damaged when you put the red lead on the (-) and the black
    lead on the (+) of a battery?

    Next question, please...
     
  2. Phil Allison

    Phil Allison Guest

    "AB"

    ** Set the meter to read DC, if there is no reading the wart is AC or dead.

    Set the meter to AC - see which it is.


    ** No.


    ........ Phil
     
  3. You CAN measure DC on the AC range. However try a high DC range low enough
    to get some indication. If the polarity changes when you reverse the probes
    it's a DC supply.
     
  4. Phil Allison

    Phil Allison Guest

    "Homer J Simpson"
    ** Only with some DMMs - most have a blocking cap.


    ** Bollocks.

    If you get a reading on the DC range - the wart is DC.

    DMMs reject AC signals on their DC volts ranges.




    ....... Phil
     
  5. AB

    AB Guest

    I know to start manually on the highest scale and work your way down
    when using it on unknown voltage etc (or use AUTO scale), but I was
    wondering about if you wanted to measure the voltage from say, an
    unknown/unlabeled wall wart. If you don't know if the end voltage is
    AC or DC how do you proceed?

    Can you damage the DMM if you try to measure AC on the DC settings or
    vice versa?
     
  6. Chris

    Chris Guest

    Start with the DMM on high AC volts and get a measurement. If it's
    reading zero, switch to high DC volts and dance down.

    A good DMM won't self-destruct trying to read AC volts on a DC range.
    Some cheaper DMMs will, though, especially if you put them on DC and
    try to measure line voltage AC (although the display will be all over
    the place). For a low voltage wall wart, though, it shouldn't be
    lethal even for the cheapies.

    Good luck
    Chris
     
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