How to Use a Multimeter- The Basics.

Adam Mechanic

How to use a multimeter for electrical testing. Please like and follow for more content.

Transcript

00:00hi everyone just a quick video on a multimeter what it is what it does and

00:05how to set it up if you're going to use it so first thing you need to know when

00:08using a multimeter is what obviously you want to test and how you want to test it

00:11so first up there's two types of electricity that you might test with a

00:15multimeter there is AC which is alternating current and DC which is

00:21direct current alternating current is anything that's generated you can only

00:25produce or generate electricity in AC form so an alternator on a car would be

00:29AC a power station's AC and the household supply that you get from a power

00:34station at your plugs is all AC and the other one is DC so the DC is the only

00:39way you can store electricity is in DC so all the batteries in the world are DC so

00:43most car systems run off DC batteries because the battery is part of that

00:46circuit there are some alternating current sensors on a car but the vast majority

00:52of your tests would be DC and obviously some electric and hybrid cars do have AC

00:56sections in them as well but 99% of the tests you're going to do on a normal

00:59internal combustion engine car will be DC and so with the multimeter itself it'll

01:05test three different things on all of them there are some other things but the

01:09first the three major things it will do it will test resistance in ohms it will test

01:20voltage in volts and it will test current in amperes or amps as everybody calls it so those are the three

01:38things that a multimeter will do so I'm going to go through each of the settings how to set it up and

01:43how to use it for each of those things so resistance in ohms is the amount of energy lost in a circuit so no

01:49circuit is perfect every single connection every bit of wire degradation around that circuit you're

01:55going to lose efficiency and you're going to lose energy so with this multimeter here and

01:59this particular setting at the top here this is the ohms one so that's your omega sign there

02:03which indicate ohms you can have 20 million all the way down to 200 ohms if you don't know what you're

02:10expecting the golden rules always start at the top one at the moment it's turned on but there's no leads in

02:15so that number one sometimes it's an ol for open loop indicates as an open circuit it's not getting

02:21a reading for this particular test you need to get your multimeter earth lead it's not technically an

02:27earth but it always goes black in black so common stands for common earth and then you get your red lead

02:33it doesn't matter if you put these in the wrong way around they are just color coded it doesn't affect

02:36the usage of the multimeter you've also got 10 amps or 2 amps and then volts and resistance that will go in

02:44there so if i don't know what i'm expecting uh for resistance then what i would do is i'd set it on

02:51the highest setting if i use this halogen bulb as an example and put my two leads across it i'll get

02:57zero that's telling me that the circuit is actually uh complete but it can't give me a reading because

03:03i'm not on the right setting so i would then drop down my multimeter until i get a reading that i want

03:09again if you're not sure just do it one at a time you'll keep getting zeros for me i know it's not

03:14going to be high resistance in a small bulb like this so i'll put it on the lowest setting

03:18and then what it will do it will give me a reading of how much ohms uh resistance is lost uh through

03:24the wiring within this bulb so um yeah that's how you do resistance test if you're not actually bothered

03:31really about whether how much resistance in the bulb having understanding what resistance in the bulb is

03:36very good if you've got multiple things to test so four splat plugs four ht leads at the same length

03:41doing a resistance test and find out the amount of ohms in each one

03:45is really useful because you can actually compare them and figure out which is the one that's gone

03:50faulty or has high resistance if all you want to know is whether this bulb is complete or the wiring

03:54inside is complete there's also this uh speaker setting here our diode test which is called it's just

04:00a continuity test so it's just checking is the wiring inside the the test component continuous

04:08and all you do is get a buzz and that's telling me the wire inside that bulb is okay and then you can

04:12move on to the next part of your diagnostics so that's the ohm setting uh the resist for the resistance

04:18the next one is volts uh measured obviously voltage uh measured in volts so on your multimeter you'll

04:24have two different ones a straight line with some dashes underneath is dc and the wavy line is

04:30alternating so that's ac so if you were working on uh finding how much current was coming to a plug in

04:35a house you'd use this scale if you're working on anything on anything on a car really or that comes

04:40off a dc battery you'd use the dc scale again if you are not sure start on the highest setting and work

04:46down if you're working on a car battery they're always 12.5 to 12.8 volts if they're healthy so you put it on

04:52the 20 setting and then you put the multimeter leads onto the circuit so the thing with voltage is

04:59you don't break the circuit all you do is take a reading from it so i've had my car battery here i'd

05:04take a reading from it if you get the leads the wrong way around it doesn't matter you'll just get

05:07a negative sign rather than a positive all you're doing is taking a reading from the circuit so when

05:12i put these two leads on a car battery and it says 12 and a half 12.5 volts all it's telling me

05:17is the difference voltage difference point to point so across that battery the difference

05:22because volts is pressure uh so the push for the current so it's telling the difference in push

05:28from the positive post the negative is 12.5 volts you can't injure yourself or do any damage doing

05:35a voltage test because you're making your own circuit against an existing circuit so you're not

05:40breaking into the circuit and disturbing it anyway you don't have to just do it across a battery so you

05:44can do point to point anywhere in a car so you could go from the battery to the alternator go from the

05:50battery to a starter motor from the battery to a switch in the car and just see how much voltage

05:56is lost point to point obviously there's two sides to every circuit there's the positive side of the

06:00negative so do bear in mind if you're doing that sort of test but generally speaking just take a

06:06reading from a circuit and you'll see the voltage drop obviously bear in mind that circuit needs to be

06:10turned on so if you're doing a voltage drop test from battery to a bulb make sure you turn the lights on

06:16otherwise you won't be getting any readings so that's the voltage test again start at the top

06:21and work down like i keep saying and the last one is amps uh which is this one again you've got a

06:27dc and an ac so again depending on where you are uh what you're doing uh will determine which

06:33of those settings you put it on so on this particular one i'll do dc because obviously dc amps is what i'd

06:39be using in a car you've got 10 you've got two then you've got milliamps and then um micro amps so

06:48those are at 1000 for milliamps so you've got amps milliamps uh micro amperes so lots of different

06:56settings there the one thing people get wrong quite often is if they put it on 10 amps and they think

07:02they put it on volts that will blow the fuse that sat inside this multimeter 12.10 amps is a lot lot less

07:10uh than the equivalent of 10 volts a 12.5 volt battery could uh push 700 amps so make sure that

07:18you put it on the right setting before you put the test leads on you can't blow the fuse on the

07:22multimeter on on voltage and you can't damage it on the resistance side but you can damage it on the

07:27amp setting obviously depending on which uh amp setting you're using you might have 10 amps

07:332 amps so just on 10 you'd use that one anything lower than that from 2 amps

07:38to milliamps to micro amp amperes would all be in that setting there and as i didn't mention before

07:44if you look on there they've got voltage and ohms so that's the same part for that

07:48so hopefully that makes sense you've got your resistance in ohms you've got dc volts ac volts

07:55uh dc amps and ac amps on this particular multimeter you do get other ones like this one here where it will do

08:02certain things like there's temperature setting and so on um but most of them do the same obviously

08:07bear in mind that some are rated differently this one's a category three which would be fine for

08:11electric vehicles and hybrid cars because it goes up to a thousand volts and it'll say category

08:16three here so do bear in mind if you're buying one that it's rated for whatever test you need to do

08:21i hope that's helpful and it makes sense and uh we'll see you next time thank you

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