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EEVblog #26 - Multimeter Tutorial - Counts, Accuracy, Resolution & Calibration

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    Hi! Welcome to the EEVblog.
    I'm your host Dave Jones
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    and this is episode number 26.
    There was a comment on one of
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    my earlier blogs from
    someone called Walter.
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    He had a question about multimeters and
    the counts like a 4000 count multimeter
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    What are counts and how that
    relates to multimeter accuracy.
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    I thought that's a pretty good question.
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    It's something a lot of people
    don't understand all that well.
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    So I thought I'd clear it up.
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    A 3½ digit meter can actually
    display plus or minus 1999.
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    The half actually means that the most
    significant digit can only go to one.
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    It can only be zero or one.
    So a 3 ½ digit meter can go up to 1999.
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    A 4½ digit meter can go to +/- 19999.
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    They've started advertising 3¾ and
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    three-quarter digits or
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    three and two thirds digits and that's
    where it gets a bit confusing is very
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    real
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    standard for that but Tom typically if
    it if it's not like two-thirds of three
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    quarters
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    or something like that by reeling main
    that he can go a bit faded with them
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    once thought might be
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    I'm 3 know I know I know I know it might
    be to
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    999 or even Fort 9900 something like
    that
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    not because it started becoming quite
    confusing
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    manufacturers started talking in terms
    is our
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    the number of care what's and I think
    this is a much better way to do it
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    so I i three and a half digit multimeter
    at plus/minus 1990 is actually
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    a 2000 count me to because it counts up
    to
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    plus/minus 2000 and likewise before and
    after each meter is actually a twenty
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    thousand county can use these tents
    interchangeably
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    now has this relight accuracy well
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    it actually doesn't rely lauter nothing
    to do with accuracy so let's talk about
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    this
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    now accuracy is a term when it comes to
    motivate his people get
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    roll all the time and mining I'm guilty
    of sin at 23
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    she laziness or and I have it it's wrong
    to side
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    that this may die has and accuracy
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    a four-and-a-half digits or an accuracy
    of 10,000 carrots
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    that is completely wrong the
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    camels the number I've I am
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    digits is the resolution so it's
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    you shoots I that this may not has a ten
    thousand count
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    resolution not a ten thousand count
    accuracy
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    and if you unite if you say the wrong
    thing
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    Mike use a market adults especially if
    you're in a job interview or something
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    amass a question I can make you look
    like you don't know it
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    talking about okay now let's take a look
    at
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    of three typical mode he made his and
    hell
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    the the number of digits for the
    resolution
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    fix I'm the usability of these made its
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    now I've got a fluke 79 series 2
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    he at now this is i on 4,000 kill
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    or three and three-quarter digit made up
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    I've got made me in 37 X sake and
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    this one is a 10,000 count made a
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    the flick 87.5% he is I to
    four-and-a-half digit made up but I've
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    got it in
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    it's actually got a mud that he's
    actually I'm 6,000 count low
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    okay don't fade in the Sun Bowl teaching
    two or three
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    mayes and you can see they all read
    fields love it and I've is this slight
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    differences they
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    but let's have a look what happens when
    Roy chein the only jockey
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    K now if I had a three and a half
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    digit me to heal which I do it it
    wouldn't actually dropped down to two
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    decimal places
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    because it would have been over the one
    know and I know I'm limit
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    but none of her reach that yet so let's
    keep turning this up
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    K&C which one
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    actually dropped its range first
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    and I'm sure you can guess which one its
    gonna pay
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    being a there it is the flu
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    seven or eight series 2 because this is
    a four thousand count major
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    we r others I that 4,000 where
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    basically over four so it's got it go up
    to the next highest
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    range so we lose one digit all
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    resolution okay not accuracy now
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    week a tennis up foreign
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    that the flick a 75 here is a 6% sales
    in Kansas in as a guest to six
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    or just slightly II Bay its
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    Chinese upper range also I so I this is
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    up Dale these are giving the signs
    resolution okay this is a much more
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    expensive made up
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    I'm at six thousand chaos I K but
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    its but we've got the sign resolution
    know this maiden name
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    37 XIII 10,000 count you'll still get
    him
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    the extra digital resolution and this
    won't change ranges I'm to a guy right
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    up to a
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    and to your casa no i know i know i know
    i limit and being a race
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    after just they're all back on an even
    playing field but let's switch
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    the fluke 87 52 for her digit night
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    okay now we've got this extreme teacher
    a resolution he
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    not accuracy resolution now you for it
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    that this ID 7542 hostage it may be that
    is useful
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    until once again we get up to
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    game we get up to twenty adults and
    bingo it's going back
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    so you can save that for her digit made
    up only has more resolution for twenty
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    percent of its range
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    ok the 10,000 count me to
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    I said before that resolution the number
    digits on the sly has nothing to do with
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    accuracy n that's true
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    I K accuracy of the made-up is
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    based on the percentage of the actual
    reading
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    not a false Kyle so I made his accuracy
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    will be specified as the percentage of
    the Radian
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    plus camps now I typical
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    lie a good made up might have point and
    accuracy of
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    no 0.1 percent plus to
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    camps now what that means is if you're
    measuring
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    one fault okay you have an it
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    it will have and uncertainty all plus
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    or minus one Miley vault
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    .1 percent a one-vote is one million
    baht
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    but you have to add on two camps to that
    plus or minus
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    to Celts to get displayed value
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    saw it it will be if it's actually
    raining exactly one vote
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    okay 1.00 0
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    then it can actually be I one
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    point 0 0
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    the re or plus/minus
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    for lockport no I'm 9
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    7 so that's resolution and accuracy
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    now let's talk about calibration
    everyone knows
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    that unite you should get you made a
    calibrated
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    was actually many what it means is that
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    the meda has been checked it's been it
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    doesn't calibration does not mean
    adjustment will be made when you see in
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    this away for calibration
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    its they usually don't adjusted what
    they would do
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    is all measure it against a reference
    stain did
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    and I will give you 80 s report for
    these
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    I'm giving you the actual typically
    giving you the actual fee got
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    and you know and the a rock against that
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    absolute reference all that transfer
    stain
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    and what you do with that calibration
    information determines
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    help this morning made is going to be
    used
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    within your company one applications
    it's going to use for and how often you
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    going to calibrate
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    now just because a meter has been
    calibrated yesterday
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    does not mean it's going to be within
    spec
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    to die its I it's all about calibrations
    about the history of this made at
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    Racine's best traceability
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    in a bit rice not the calibration of
    this may DNA test article
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    record of it overtime and then you build
    up confidence
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    in this may tap that it's not drifting
    this is why some companies in some
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    industries will actually I to unite you
    have to actually use
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    to the mall he made is too tight I'm
    measurement just in case one of them
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    has unite is is actually help and I will
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    unite anyone serious about electronics
    will actually have to multimeters I want
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    rely on just
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    one though have to you so that you can
    cross check each other
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    and you can actually use a good known
    Mon made a as I
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    as a bit of a transferred stain did to
    not check
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    and measure other instruments and if
    you've got a punch him only made as you
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    can all cross measure
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    themselves and you get more confidence
    that you made a is within
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    specification usually you follow the
    manufacturer's recommendation which my
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    peace I every 12 months
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    but when you first get used to it you
    might wanna calibrated
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    more often so that we build up more that
    reference
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    that historical reference data so you
    can track it
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    and one Chino this mater is not you have
    to really stable it's not true 15 at all
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    then you might actually widened here I
    period of calibration
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    12 months then United still has
    interested or you might actually change
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    it to you
Title:
EEVblog #26 - Multimeter Tutorial - Counts, Accuracy, Resolution & Calibration
Description:

A tutorial about digital multimeter measurement display counts, accuracy, and calibration.

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Video Language:
English
Duration:
09:57

English subtitles

Incomplete

Revisions