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using a multimeter.

Discussion in 'Electronic Basics' started by Mr. Me, Apr 8, 2007.

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  1. Mr. Me

    Mr. Me Guest

    my father left me a multimeter (Ideal 61-360) and I would like to use it on
    the following. I never used one before and was wondering if anyone could
    help me with the following.

    Test for ground.

    Test if Fuse is working. im thinking that has something to do with ohms but
    still dont know how to do it.

    if anyone could help me with these things it would be great.

    Thank you

    John
     
  2. Please learn some basic safety rules before working on live circuits. Even
    low-voltage circuits can cause a serious and potentially dangerous arc.

    Ground checking can be a bit tricky. You must have a ground reference that
    you are sure of. For example, if you are sure a metal box is grounded, then
    you can check the resistance between it and a ground wire to establish the
    integrity of the ground wire (should be near zero ohms). Use the ohms
    function but only after you are certain the circuit (wire) is not live. You
    can start with the voltmeter to determine this (again, you must be careful).
    Near zero ohms for a good one and infinity ohms for a blown one. Be sure
    the circuit is dead (better yet, remove the fuse before testing).

    Never put the meter leads across a voltage source when the meter is set to
    measure current. To measure current, one breaks into a circuit by opening
    it and then completes it using the meter.

    Others will no doubt add to this.
     
  3. Chris

    Chris Guest

    Hi, John. The Test-Pro® Multimeter 360 Series is a good, rugged DMM.
    Doesn't autorange, but it's a reliable piece of electrical equipment.

    To test for ground, first put your DMM on AC Voltage, 600V range, and
    measure for *any* voltage. Click the ranges down to the lowest AC
    range one at a time, again looking for *any* AC voltage reading. If
    you get down to the 2000mV range without any reading, then switch the
    ohmmeter to the 200 ohms range, and touch the leads together to see
    the reading for zero (should be tenths of an ohm). Now measure the
    resistance between the point in question and a known ground point.
    You should still be reading tenths of an ohm, possibly a few tenths
    more than your "zero" reading.

    To test fuses, a good first check is to measure across the fuse on the
    600VAC range, and see if there's any AC voltage across the fuse. Most
    electrical fuses of more than 1 amp rating have a resistance of less
    than 1 ohm, and will basically read either 0VAC or a few tenths of a
    volt AC, or if they're open, will read line voltage across them.
    Household screw-in fuses and many others can't be measured this way,
    though. You have to pull them out, and measure ohms. Again, fuses
    rated for more than one amp should be either zero or a few tenths of
    an ohm, measured on the lowest ohms range).

    As always, be careful when measuring around line voltage. Make sure
    it's safe before you take the measurement, and never measure line
    voltage with the meter set on anything but AC volts. If you don't
    know what you're doing, ask a friend. Take the time to go to the
    library and take out a book on basic house wiring -- you'll learn a
    lot.

    Good luck
    Chris
     
  4. Mr. Me

    Mr. Me Guest

    Hello Chris and Charles:

    I would like to thank you both for the safety and how to's. I hope tonight
    I will be able to try a few of the things you mentioned.

    thank you again.

    John
     
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