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Help understanding my new multimeter

Discussion in 'General Electronics Discussion' started by otacon, Nov 10, 2014.

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  1. otacon


    Nov 7, 2014
    I just bought my first multimeter and learning how or use it. I was able to read the voltage across an LED, read resistance, and test continuity. Yet I'm unable to read the current. All I get is 0.01 (and sometimes 0.00).

    I'm guessing my multimeter is reading fine, but the current is in the milliamp range and my multimeter is displaying amps. Is there a way I can get my particular multimeter to read either in milliamps, or display more digits so I can manually convert to mA?

    Also. I noticed there's an mA option where I'd normally insert the voltage cable/probe. Maybe I should connect there instead of the separate slot that says 10A max. I don't know :( I just want to properly read the current.

    My circuit:
    Two 1.5v alkaline AA batteries ----> 100ohm resistor ---> LED ----> negative multimeter probe --> back to battery through positive multimeter probe

    Hope this all made sense.
    Multimeter: UNI-T UT33D

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Assuming you have a red LED, your meter should show approx. 10-15mA
    Insert the test leads into the center and right connectors (you're right, the 10A range will be useless for 10mA).
    Set the rotary switch to "A= 200m" first. The meter should now display the current. If the current is, as expected, below 20mA, set the rotary switch to "A= 20m" for a better resolution of your measurement.

    When measuring unknown currents, start in the highest possible range and select a lower range only if the result in the higher range is not well resolved. This will help to protect the meter from overcurrent.
    otacon likes this.
  3. Bluejets


    Oct 5, 2014
    You are correct to place your meter leads in series with the circuit.
    However, it is a little difficult to follow your explanation of what you had selected and what you had plugged in where so follow this.

    common is black meter lead
    For DC lead will go into the socket marked V ohm mA (centre socket.)
    Selectot switch will go to the A range where it says 200m...this is 200mA

    20m is 20mA
    2000u is 2000uA or 2mA

    For high DC currents,(Amps) meter leads go into common
    Red meter lead goes into 10A max
    Selector goes to 10 on the A range
    However I doubt the leads supplied with this meter would stand up to high current for any period so take care there.

    Do not use this meter for anything other than low voltage testing.
    It is Cat1 only...... i.e. not for testing power outlets etc.

    Remember to switch your meter back to some voltage range after testing DC current.
    It would not be the first time this was forgotten and the leads placed to test a voltage while still on the mA range and then blow the internal fuse.(usually 2A ...1AG size)
    otacon likes this.
  4. otacon


    Nov 7, 2014
    Thanks Harald!

    Thanks for the response Blue, didn't notice it until now.
    Last edited: Nov 10, 2014
  5. otacon


    Nov 7, 2014

    When you say switch back to some voltage range after testing DC current, can I switch back to OFF, or specifically to some voltage range?
  6. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Off will safe your battery :)

    Switching to a voltage range just prevents you from accidentally short-circuiting a circuit when you want to measure a voltage but have the meter in current range.
  7. otacon


    Nov 7, 2014
    Thanks Harald, that answered my question! Next time I'll get a multimeter that has a separate connector for mA. I've read meters with mA and voltage in the same connector are easier to fry.
  8. BobK


    Jan 5, 2010
    Actualy, having a separate mA connect might be worse. In that case, you would blow the fuse even if you had changed the range to voltage but forgot to move the test lead.

    BTW: I blow that fuse regularly, I keep spares on hand. Often there is a spare kept inside the meter case.

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