How to Use a Multimeter
How to Use a Multimeter
This video will show you how to use a multimeter to measure voltage, current, resistance, and continuity. This is a beginner’s guide aimed at students and electronics hobbyists who need to make basic measurements using an entry-level multimeter. For additional details, see the written tutorial on our website: https://www.sciencebuddies.org/scienc…
0:00 intro
0:54 multimeter probes
1:23 multimeter labels
2:00 multimeter ports
2:42 measuring batteries
6:06 measuring voltage
8:05 measuring current
11:46 measuring resistance
14:08 continuity check
16:33 advanced features
If you are new to electronics, you may also find our breadboard tutorial helpful: • How to Use a Breadboard
How to replace a multimeter fuse: • How to Replace a Multimeter Fuse
Science Buddies also hosts a library of instructions for over 1,000 hands-on science projects, lesson plans, and fun activities for K-12 parents, students, and teachers! Visit us at http://www.sciencebuddies.org to learn more.
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Content
0.03 -> Hi this is Ben Finio with Science
Buddies. In this video we'll show you how
3.449 -> to use a multimeter.
6.56 -> Multimeters come in all shapes and sizes.
While professional multimeters can cost
10.8 -> hundreds of dollars, if you're a student
doing a science project or hobbyist
14.58 -> just tinkering with electronics, a
cheaper multimeter somewhere in the
17.88 -> twenty to thirty dollar range is
probably all you need. Most multimeters
21.81 -> have similar features including a screen
that displays the readings, a knob that
26.22 -> selects the measurement, and ports where
you plug in the probes to take the
29.49 -> measurement. In this video we'll be using
this DT830L digital multimeter which
34.68 -> is included in many of our Science
Buddies kits. We'll go over how to
38.339 -> measure voltage, current, resistance, and
do a continuity check, some of the most
43.499 -> common features you'll use on a
multimeter. Other multimeters might have
47.46 -> more advanced features like the ability
to measure capacitance but we won't be
51.03 -> going over those in this video.
Most multimeters come with a pair of red
56.37 -> and black probes with a plug on one end
to go into the multimeter and a pointy
60.03 -> probe tip on the other end that you can
use to probe circuits. It's convenient to
63.989 -> have some alligator clip cables handy as
those can allow you to clip onto the
67.5 -> circuit to take measurements so your
hands can be free to do other things.
70.13 -> There are different types of probe
accessories available, for example these
74.579 -> probes have a banana plug on one end to
go in the multimeter and an alligator
78.42 -> clip directly on the other end instead
of a probe tip so you don't need a
81.479 -> separate alligator clip cable. Let's
start by looking at our multimeter in a
85.32 -> little more detail. There are a lot of
symbols on the front that might be kind
88.2 -> of overwhelming and confusing at first
but don't worry we'll go over them one
91.38 -> by one as we use them. The main symbols
you'll be seeing in this video are V for
96.42 -> volts, A for amperes which is the unit of
current, and the capital Greek letter
101.07 -> Omega which stands for ohms or the unit
of resistance. This multimeter has a
105.57 -> separate on/off switch that you use to
turn the multimeter on and off. More
109.59 -> expensive multimeters usually have an
auto power off feature that will turn it
113.1 -> off automatically after a certain period
of inactivity, but this one doesn't so make
117.149 -> sure you remember to turn it off when
you're not using it in order to conserve
119.82 -> the battery. Now let's look at the ports
where we can plug the probes into the
124.649 -> multimeter. You'll see that we have three
different ports labeled COM, V Omega mA,
129.539 -> and 10A. COM stands for common that's
where the black probe is going to be
134.34 -> plugged in and we'll usually connect that
to the ground or negative side of our
138.09 -> circuit. V
Omega mA stands for volts ohms or
142.079 -> milliamps, we plug the red probe into
this port for most of the measurements
145.86 -> we're going to be taking to measure
voltage, resistance, or small amounts of
149.43 -> current, and then finally this third one
we're not going to use as often that's
153.39 -> for measuring large amounts of current
up to about 10 amps. So for now we're
157.29 -> going to plug the red probe into this V
Omega ma port. Now let's start with the
163.409 -> relatively simple case of measuring the
voltage of a battery. I'm going to set
167.159 -> the dial on my multimeter up here
somewhere in the V range, we're not going
170.819 -> to worry about the exact number yet, turn
the multimeter on, and again I have the
174.329 -> black probe plugged into the COM
port and the red probe plug into the V
178.95 -> Omega milliamp port. I have two batteries
here a double a and a 9-volt, and I'm
184.5 -> going to start out with the double a. I'm
going to take,
188.56 -> oops, the black probe and touch it to the
negative side of the battery and the red
194.69 -> probe and touch it to the positive side
of the battery. And you can see I'm
197.84 -> getting a reading of zero zero one on
the screen. And that's not a very
203.12 -> accurate reading I'm not getting any
decimal places and you'll see that I
206.18 -> have my knobs set all the way up here to
a thousand volts which if you know
210.59 -> anything about batteries is much much
higher than we expect to get from a
213.709 -> double-a battery, we would expect this to
be about 1.5 volts. So fancier
218.42 -> multimeters will have an auto ranging
feature where they will automatically
221.87 -> select the measurement range for you.
This multimeter isn't going to do that
226.34 -> for you, you need to manually select the
range that is the best for what you want
229.819 -> to measure. So what I'm going to go do
is go down a step to 200 volts and try
236.599 -> again. And now I'm getting 1.5 volts
which is about what I expect, but 200
241.97 -> volts is still a lot bigger than what I
need to measure, so I'm going to keep
244.7 -> stepping down to the 20 volt range, and
notice that when I do that I get an
249.53 -> extra decimal place, the decimal point
moved over one. So now if I measure
255.629 -> I get one point 6 volts, 1.60. So my
reading is getting more accurate so I
260.579 -> got an extra decimal place. This voltage
is actually small enough that I can keep
264.78 -> going down. Now notice that the label
here changed now I'm in the 2000 M range
271.229 -> which stands for 2000 millivolts. So now
my reading is in millivolts instead of
275.49 -> volts, it's important to pay attention to
the labels on the dial because they'll
279.12 -> tell you the units of your measurement.
Now here I don't have a decimal place any
284.25 -> more, I'm getting 1608 millivolts, so as I
keep going down my reading keeps getting
290.43 -> more and more accurate. If I go down too
far though my range won't be high enough
295.65 -> to measure the voltage. So I've gone all
the way down to be 200 millivolt range
301.77 -> and now I'm getting a one with no other
numbers which, is how this multimeter
305.699 -> tells me that the reading is outside the
current range I have selected. So if I go
309.81 -> down too far I'll get that one on the
screen, I go back up to the next highest
314.159 -> value and that's going to give me my
most accurate reading for this voltage.
317.669 -> So in this case I get one thousand six
hundred and seven millivolts or one
322.169 -> point six oh seven volts. I can do the
same thing for the 9-volt battery here
327.9 -> where you might be able to guess if I
have this set to two thousand millivolts,
331.05 -> that's two volts, that range is not high
enough so I get a 1. If I want to measure
335.22 -> that 9-volt battery I'm gonna need to go
up the next step to 20 volts and here
341.34 -> you can see that this battery has
actually actually been drained a little
344.13 -> bit, I'm only getting about seven point
nine eight volts instead of the nine
347.43 -> volts I would expect. Finally if I
reverse my probes so if I put the red
351.569 -> probe on the negative terminal and the
black probe on the positive terminal, I
356.13 -> will just get a negative number. So that
doesn't damage anything it doesn't hurt
360.36 -> anything, that just tells you that you
have your probes backwards because you
362.969 -> would expect a positive voltage when
measuring the battery. Now measuring the
367.68 -> voltage of a battery is pretty simple
what if we want to measure the voltage
370.74 -> of something in a circuit? So here I have
an example circuit consisting of a
374.789 -> battery pack a resistor and an LED, very
simple demonstration circuit, and what if
380.039 -> I say I want to measure the voltage in
this circuit? Now note that voltage is
383.94 -> measured between two points so it
doesn't make sense to just ask what is
387.509 -> the voltage in this circuit, we have to
ask which component we are measuring the
390.93 -> voltage of. In this case if we look at
the circuit diagram we can see we have
394.74 -> three components in series, we have the
battery, the resistor, and the LED, and we
399.419 -> can measure the voltage across any one
of those components individually. To
403.349 -> measure voltage in circuit you connect
the multimeter in parallel, so in this
407.34 -> case there are three different ways we
could connect the multimeter in parallel
410.94 -> to something in this circuit. We could
connect it in parallel to the battery, in
415.11 -> parallel to the resistor, or in parallel
to the LED. When taking measurements on a
420.75 -> breadboard this is where alligator clips
and jumper wires can come in handy
423.93 -> because you can just put the jumper
wires into the breadboard and then your
426.719 -> hands will be free to do other things. If
you don't understand how a breadboard
430.05 -> works or you've never used one before we
highly recommend you check out,
433.24 -> check out our breadboard tutorial video
which will tell you everything you need
436 -> to know about breadboards, but for now
we're going to assume you know how they
438.61 -> work. So first I'm going to connect my
two wires in parallel to the battery,
443.58 -> putting them into the power buses here.
You'll see I get a reading of 2.83
448.66 -> volts.
I can also connect them in parallel to
452.62 -> the LED.
458.639 -> I get a smaller reading of 2.2, roughly
about 2.3 volts and finally I can
465.93 -> connect them in parallel to the resistor
472.81 -> and I get a reading of about 0.65
volts so as I would expect with these
476.8 -> components in series the voltage across
the LED plus the voltage across the
480.94 -> resistor should equal the voltage across
the battery pack. Now what if I want to
486.25 -> measure the current through this circuit?
This gets a little more complicated. To
489.49 -> measure the current through a part of a
circuit you need to put the multimeter
492.46 -> in series with that part of the circuit.
And while to measure voltage I didn't
496.9 -> actually need to rearrange anything on
the breadboard to do that because I was
500.86 -> just putting the multimeter probes in
parallel with the different circuit
503.62 -> components, to put the multimeter in
series I'm actually going need to
507.04 -> rearrange things on the breadboard a bit.
So if I look at the circuit diagram, I
510.31 -> only have one loop in my circuit here so
the current I measure is going to be the
514.36 -> same regardless of where I put the
multimeter. I could put it in between the
517.839 -> battery and the resistor, in between the
resistor and the LED, or in between the
521.77 -> LED and the battery, the current
will be the same in any case. But when I
526.15 -> go do that on the breadboard here I'm
going to need to move one of the parts.
529.839 -> So for example I'm going to move the
resistor lead over one hole here and
536.44 -> then get ready to put my multimeter
probes in series with the resistor and
540.79 -> the LED, but before I do that I want to
be careful. Let's go back and look at the
546.4 -> ports for the probes on our multimeter
again and the settings for current.
550.06 -> Remember we have this extra port for 10
amps and if you don't know how much
555.49 -> current you're going to measure it's
always safer to start with that 10 amp
559.54 -> setting because that will allow you to
measure a much higher current without
562.51 -> damaging your multimeter's fuse. So if you
know about LEDs you might know oh that's
566.77 -> probably only a couple tens of milliamps,
you should probably be safe, but
570.76 -> especially if you're working with motors,
or something where you just in general
574.15 -> don't know the current, it's safer to
start with that higher measurement
577.839 -> because as you can see if you look at
the small print by this other port here
583.33 -> that one is limited to 500 milliamps max,
so if we exceed 500 milliamps on this
589.209 -> port we're going to blow the fuse. So we
can go all the way up to 10 amps on this
592.36 -> one,
safer to start there and we're going to
594.67 -> turn our dial over to the 10 amp setting
on the knob. So now I should be able to
602.47 -> put my multimeter
in series, you notice that the LED has
606.96 -> gone out because I broke the circuit by
moving that resistor.
610.17 -> I put the multimeter in series here, the
LED goes back on but I'm getting a
616.8 -> pretty inaccurate reading again, 0.01, I
don't know what the decimal points are
620.58 -> beyond that so it should be safe now to
move down to the port with the lower
628.17 -> current range that's going to be more
accurate. So I'm going to switch back
632.66 -> down to here, lower myself to the 200
milliamps setting and you can see now
638.85 -> I'm getting a more accurate reading of
thirteen point seven, thirteen point
642.42 -> eight milliamps. And just like I did with
the voltage I can keep stepping down to
646.98 -> get more and more accurate readings
until my range goes too low. So I can
650.52 -> step down to 20 milliamps, now I'm
getting an extra decimal place about
655.56 -> twelve point two one, all the way down to
2,000 milliamps and now I've gone too
660.33 -> low. Okay so if I go back up to about 20
milliamps that's gonna be the most
666.06 -> accurate reading I can get for this
circuit with two decimal places. Now when
671.67 -> you are done measuring current it is
always a good idea to set your
674.79 -> multimeter dial back to measuring
voltage, and that's because it is much
678.96 -> easier to accidentally blow the fuse
when you have a multimeter set to
682.89 -> measure current. For example if you
wanted to measure the voltage of a
686.16 -> battery like we did earlier, and you
connected the probes directly to the
689.91 -> battery with no resistance in series to
limit the current while you have it set
693.81 -> to measure current you will easily blow
the fuse because you're going to get a
697.11 -> lot more than 500 milliamps directly out
of the battery. So again when you're done
701.13 -> measuring current set it back to voltage
just to be safe
703.95 -> the next time you pick up the multimeter.
Okay next let's talk about measuring
708.48 -> resistance, so this is something that's
convenient if you just hate reading
712.26 -> those color codes on the tiny little
resistors or if you need to measure the
715.65 -> actual value of your resistor instead of
just a rated value because there's
720.03 -> usually a pretty big error range like 5
or 10% on the actual value of the
723.9 -> resistor. So to do that you're going to
want to remove the resistor from the
728.04 -> circuit don't try to measure resistance
while the resistor is connected to a
731.67 -> power supply in an active circuit or you
won't get an accurate reading, and
735.71 -> again here's where alligator clips come
in handy
738.93 -> to just clip on to the leads of that
resistor and just like we did with
747.529 -> voltage and current, you can make an
educated guess as to where you should
751.559 -> start on this dial, so for ohms we can go
all the way up to 2000 kilo ohms which
756.779 -> is equivalent to 2 mega ohms or all the
way down to 200 ohms. In this case I
761.639 -> started at the lower end of the range
and I have what should be a 47 ohm
765.54 -> resistor here, so I'm getting pretty
close to that, about forty six point
768.809 -> eight, forty six point nine ohms and you
can see as I go up I start to lose
773.16 -> accuracy because I'm losing that decimal
place. So measuring a resistor this small,
776.61 -> I want to be all the way down there in
that two hundred ohm range I have a
782.04 -> bigger resistor here, this one is
supposed to be about ten kilo ohms
786.829 -> so if I connect that,
790.559 -> you can see I'm getting the one because
I'm outside the range of exceeded two
793.949 -> hundred ohms and as I start going up
eventually I should get in the proper
799.319 -> range for this resistor. So you can see
again there's that error percentage this
803.009 -> is actually about ten point three ohms
not exactly,
805.709 -> sorry ten point three kilohms not
exactly ten kilo ohms, so it can be
810.449 -> important depending on what you're doing
to measure the actual value of your
813.479 -> resistors. Now with cheaper multimeters
you're not going to get very accurate
817.529 -> readings for very small resistances, so
if you're trying to measure something
820.949 -> just like a wire this is usually
probably down around one ohm or even
825.809 -> less than that, don't trust those
readings too much. You can see I can
831.719 -> connect to this wire and go down to my
smallest range and I get something like
835.799 -> 1.0 ohms but really below and ohm your
reading is not going to be very accurate
840.089 -> with a cheap multimeter so make sure you
use this to measure actual resistors but
844.259 -> not just pieces of conductive metal or
wires. The final feature we're going to
849.509 -> go over is the continuity check so
that's this little symbol here with kind
853.259 -> of those little curvy lines and the
arrow symbol which represents a diode if
857.159 -> you know what a diode is, and this one is
a really convenient feature that just
861.209 -> beeps if two things are electrically
connected. So if I touch my probes
865.709 -> together directly [beeping] it beeps at me because
there's a complete conductive path for
872.459 -> the circuit or the current to flow
through the circuit there. This is a
875.369 -> really convenient feature to check if
two things are connected like they're
878.489 -> supposed to be in your circuit or for
example to check if a cable is good. So
883.529 -> for example let's take my circuit here,
put my resistor back in
891.05 -> and say I don't know if maybe I have
something wired improperly I want to
897.12 -> make sure that there's a conductive path
between this leg of my LED and this wire
904.079 -> on the battery [beeping] so that's telling me that
there is a path between this part of the
909.779 -> LED and there. So say I had this wired
improperly, say had the resistor in the
914.879 -> wrong hole, and my LED is not lighting up,
then I can test both sides of my LED. I
921.12 -> can test here and say okay I know [beeping] I have
conductivity on this side those are
927.42 -> connected because I'm getting a beep, but
if I test on this side there should be a
929.819 -> connection between the LED and the
resistor, but I'm not getting a beep
934.949 -> there. Then if I look more closely I
could realize, oh I have that wired
937.92 -> improperly I don't have conductivity
between this leg of the LED and this leg
942.149 -> of the resistor. Similarly say you have
an experiment with a bunch of wires or
947.399 -> cables and you're not sure if maybe you
kinked a cable or broke something or if
950.91 -> you have a cable that's going bad yeah
if I take this alligator clip and touch
955.68 -> the probes to both ends the alligator
clip [beeping] I'll get a beep letting me know
961.079 -> that my cable is good if I didn't get a
beep and I'd know that this cable is
963.99 -> probably bad. So again, a convenient
feature that you can use to test for
968.069 -> conductivity in circuits or test if a
material is conductive. For example if I
972.149 -> touch these two probes to a piece of
metal say like the outside surface of
976.259 -> this battery [beeping] I know that's conductive
but if I touch it to the paper on my
983.43 -> work surface here that's not conductive
because paper does not conduct
987.509 -> electricity. So also a convenient check
to test if a material is conductive or
991.68 -> not. Again there are some more advanced
features on this and other multimeters
996.42 -> that we didn't go over in this video, you
might have noticed this NPN and PNP
999.779 -> thing down here that's for measuring
transistors, there's a V with a squiggly
1004.25 -> line next to it for measuring
alternating current instead of direct
1007.129 -> current. You can measure the voltage from
a wall outlet, we don't recommend doing
1011.779 -> that if you're new to electronics
because wall outlets are actually
1014.87 -> dangerous and you can hurt yourself if
you don't know what you're doing, whereas
1017.54 -> the electricity from batteries and
little battery-powered circuits like
1021.259 -> this is generally pretty harmless, so
this is much safer if you're starting
1024.079 -> out.
We're not going to go over those in this
1026.12 -> video but if you have any more questions
about anything you saw in the video in
1029.81 -> more detail we recommend you check out
our written tutorial, there's a link to
1033.08 -> that at the end of the video and have
fun using your multimeter in your
1036.17 -> project.
Source: https://www.youtube.com/watch?v=ts0EVc9vXcs