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What are ways in which a multimeter can "break"?

  1. Sep 5, 2014 #1
    The digital multimeter I have says

    "Overload protection: F 250mA/250V Fused
    (10A range unfused)
    Max. Input Current: 10A
    (For inputs >2A: measurement duration<10 secs,
    interval > 15 minutes)"

    It also says in the manual that the 10A jack is not fused

    So what I am wondering is since the max AC input is 750V what happen if I try to read a voltage of 1000V. Also what does the 'fuse' do, 2 jacks are fused except for 1....
     
  2. jcsd
  3. Sep 5, 2014 #2

    DrClaude

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    Staff: Mentor

    Have you ever heard of "burning"? :wink:

    If you're using the fused jack, hopefully the fuse will burn first, leaving the rest of the multimeter intact, such that you only have to put in a new fuse to have it working again.
     
  4. Sep 5, 2014 #3

    AlephZero

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    I would translate a spec like that as "the marketing department told the designers to include 10A and 1000V input ranges because they look cool in the advertising, but they aren't actually useful for anything much in real life."

    If you exceed the maximum ratings and get lucky, some sort of "out of range" indicator will show on the display. If you don't get lucky, there will probably be some combination of blown fuses, sparks, bangs, smoke, flames, a permanently destroyed meter, and/or the user recovering from an electric shock.
     
  5. Sep 5, 2014 #4

    Integral

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    Gold Member

    LOL! So you think no one ever measures current over an amp or so. Any time you have much over an Amp you need the 10A range. I use it often.

    I suspect that 1000V on a normal meter would let the smoke out. Experiment at the risk of your meter.
     
  6. Sep 5, 2014 #5

    AlephZero

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    The idea that a meter has protection on the low current and voltage ranges but not on the high ranges seems bizarre - a bit like wearing a parachute while planning a flight but taking it off when you get in the plane.

    Of course there are handheld digital meters that can measure 1000V and 10A safely, e.g. http://www.test-meter.co.uk/images/file/AVO410.pdf, but serious measurement tools don't have restrictions like "measurement duration 10 sec, interval between measurements > 15 minutes".

    You can get high voltage and current probes to measure up to 400,000V or 1000A with a "standard" meter, if you need that capability.
     
  7. Sep 5, 2014 #6

    nsaspook

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    It's pretty hard to protect a small wattage 0.1 ohm shunt resistor in a hand-held meter from a high energy source with a fuse when the fuse resistance is in the same range and increases the measurement burden voltage. The meters safety specs are mainly for human protection and don't protect the meter from abuse. It won't blowup in your face from a high energy source if it's a quality meter but there's no guarantee it will still work. I ran the electronic measurement calibration dept at work for years and it never ceased to amaze me the creativity a tech could use to smoke an expensive meter.

    NSFW language.
    https://www.youtube.com/watch?v=Ewyf9mzIfi0
     
    Last edited: Sep 5, 2014
  8. Sep 19, 2014 #7

    CWatters

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    Dont. High voltages are dangerous. The insulation on this meter may only have been designed to protect you from 750v. The meter may or may not be damaged as well.

    Before measuring anything you should have some idea what the maximum is likely to be and set the range accordingly. Setting it too high is unlikely to cause damage. Setting it too low might well cause damage. You can always turn the range down if you set it too high.
     
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