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Tips on DMM for a newbie?

Discussion in 'Electronic Basics' started by Rui Maciel, Jul 14, 2010.

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  1. Rui Maciel

    Rui Maciel Guest

    Can you spare any tips on DMMs for newbies?


    Thanks in advance,
    Rui Maciel
     
  2. Phil Allison

    Phil Allison Guest

    "Rui Maciel"

    ** DMMs use probes - not tips.

    Fuckwit.


    .... Phil
     
  3. Rich Webb

    Rich Webb Guest

    If it's the "on-off switch" type and not the "rotate to turn on and
    select the function" type then get into the habit of leaving the DMM set
    to a moderately high voltage range when you're finished with it.

    That prevents those unfortunate learning experiences when one picks up
    the DMM for the first time in a month intending to measure a voltage
    source -- but it was left in an amperage range and <poof> blows the fuse
    (if you're lucky) or the meter (if you're not).
     
  4. Buy a cheap one, and start using it. You'll then learn from experience
    what is there, and get a better idea of what you might want in the way of
    a better DMM. Someone already pointed out the need to be careful or
    you'll wreck the meter, a beginner is far more likely to make mistakes
    than one with experience, so buying a cheap meter means you won't lose
    much if/when you do damage the meter. Or your interest in electronics
    won't last, so you haven't spent too much on it by buying the cheap meter.

    People could supply a list of "needed test equipment", but you have to be
    the judge of what you need and can afford, but you won't get to that point
    until you've actually started doing things. So when you can, it is far
    better to start with used or cheap equipment, to get a feel for it, which
    helps you to make an informed decision when/if you need something better.

    I bought my first oscilliscope at an amateur radio auction for five
    dollars, it was horrible, heavy and very old almost forty years ago,
    but it gave me something to play with, which at that point was mostly what
    I wanted a scope for. I learned the basics, and then learned how lousy
    that scope was. That seems to be a better situation than being told
    what you need, spending the money, and then not knowing what to do with
    the scope.

    Michael
     
  5. Rui Maciel

    Rui Maciel Guest

    Good point. Yet, there are tons of cheap portable DMMs on ebay which, besides external appearance
    and what sort of battery they take, appear to lack any relevant difference. Are there any features
    that I should look for?

    Thanks for the tip, Michael. You do make a good point.


    Thanks for the help,
    Rui Maciel
     
  6. Rich Webb

    Rich Webb Guest

    A backlight for the display is nice to have.

    A "true RMS" meter may be useful on the AC ranges. On the other hand,
    the non-"true RMS" meters are set internally to convert average to RMS
    for sine wave inputs so, as long as what you're measuring is pretty
    close to a sine shape, the results should be close enough for most
    purposes. If you really need a 0.1% or better RMS value for odd-shaped
    waveforms, you'd probably already know.

    Pick up a set of inexpensive banana to mini-clip (or alligator) test
    leads. That lets you clip the DMM to the circuit's ground reference and
    frees up one hand to do something else, or to clip one to ground and one
    to a test point to leave both hands free while you adjust the gizmo.
     
  7. Phil Allison

    Phil Allison Guest

    "Rui Maciel"


    ** That is because, essentially, there is none.


    ** You are just another boring, PITA fuckwit troll trying to make your
    pathetic case of purchase anxiety over a $10 item into our problem.

    Lemme tell ya - it fucking aint !!!!



    ...... Phil
     
  8. Tom Biasi

    Tom Biasi Guest

    Check the position of your probes every time. Many meters have no fuse in
    the 20 Amp. position and trying to measure line in this condition will be
    dangerous.

    Tom
     
  9. Jamie

    Jamie Guest

    Jesus Phil, is our language that hard to comprehend or you guys
    down under just don't get it?

    P.S.

    This should start a fire ball of two!

    :)

    Jamie
     
  10. Jamie

    Jamie Guest

    Go to a harborfreight store, if you have one near by or order on line..

    They have some that will be fine for first timers..
     
  11. here's a few tips

    if the meter has a current range, it will act like a short circuit across
    the probes. The meter will either blow a fuse or just burn out if you set
    it to say a 250mA range and connect it to a large battery or an outlet.

    In the volts range, it's much harder to break the meter

    measuting the currents and voltages in a flashlight is usually pretty easy
    and will let you learn what the meter is doing without breaking anything.

    When a DMM acts weird, it may be time for new batteries, even if you think
    they are still good.

    if the meter has a diode check or continuity mode, it can usually run a
    LED, at least if it's a red one.

    measure whatever you can, like the output of power supplies that plug into
    the wall or stuff like that. The more you do something, the more familiar
    it becomes and the more sense it makes in the end.

    Electronics is a hands-on activity.
     
  12. amdx

    amdx Guest

    ah Phil, sounds like you got up on the right side of the bed.
    Mike
     
  13. Phil Allison

    Phil Allison Guest

    "Jamie"
    ** Nope.

    But the fuckwit OP needs to learn how to post a meaningful question.

    Cos what he just post is not one.


    ..... Phil
     
  14. Jamie

    Jamie Guest

    those things are sold and have been sold in a variety of inners with
    all kinds of different names on them...

    I still have some older ones I got that allows you to tie the
    common of the bat to the common input. Makes for a quick hack display..
    Most of the ones they have now won't let you do that, even though they
    look the same on the out side. Different board.

    I think I paid like $3.00 each from a tool flea market.
    I got a arm full that day... They make good wheel wedges and
    don't hurt so much when they fail!
     
  15. Fred Abse

    Fred Abse Guest

    They're the ones to avoid. I wouldn't countenance a meter with an unfused 20
    amp range. There's a video on the Web (Link from the Gossen site, IIRC) of
    a TÜV test on a DMM that'll make the point.

    The Fluke 80 series (fused) alarms if you have a lead in either current socket with
    a voltage or resistance range selected. Not totally foolproof, but it's
    better than nothing.
     
  16. Fred Abse

    Fred Abse Guest

    Portugal.
     
  17. Fred Abse

    Fred Abse Guest


    Do you mean advice on which DMM to buy, or advice on using a DMM?
     
  18. Tom Biasi

    Tom Biasi Guest

    Agreed, but since he is looking for a cheap one it is likely that he will
    come across such a meter and I thought he should be warned.

    Tom
     
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