Summary

Your multimeter can do more than you think. Learn how to properly test voltage, resistance, and continuity to diagnose real wiring faults fast.

00:00 Hey everyone, welcome to today's webinar.
00:02 I'm Caleb here at High Performance Academy.
00:04 It's great to have you here with us and today we're going to be talking about multimeters.
00:09 It's probably one of the best pieces of equipment you can have for testing when it comes to electrical but there's generally a lot of you know little dials and symbols that everyone might not know what they are actually referring to.
00:21 So, we're going to have a bit of chat about that and look over a few different multimeters that I've got here, some different scenarios when you're using them to test in an electrical environment.
00:31 This is a recorded webinar, but if you can't watch the whole way through or you need to watch it at a different time it is recorded and then saved up to our archive and you'll be emailed about it and you'll be able to watch it at a later date if you need to.
00:44 But if you do stick around with us today we are having the Q&A at the end which is a good opportunity to ask some questions and get answers from me directly.
00:52 I'll say yeah just leave them to the end.
00:54 Near the end I'll give you a couple of prompts to start checking those questions in the chat.
00:59 I might answer some questions naturally as we go, so don't get flooded with questions we'll just hold off a little bit to the end.
01:06 Also I'm going to mention the 2JZ giveaway that we're doing that's a pretty epic build and giveaway.
01:13 I wish I could enter, but unfortunately I can't being a part of HPA.
01:18 I definitely recommend all you guys get a part of it because that is going to be as I said an absolute epic giveaway and just build in general so, keep an eye on that one.
01:28 So, let's get stuck into multimeters.
01:31 They range quite a bit in price you can buy quite cheap ones I've got most of the ones I've got here are I think around the sub $200 range.
01:40 The Digitech on my far left here is in the sub $100 range, so you can you know get them in quite a different price range.
01:47 They do have you know you get what you pay for sort of situation you can bump right up to a Fluke multimeter for hundreds of dollars, but they are definitely worth it and they're definitely more accurate.
01:59 I find that's probably one of the things that you don't really notice a lot with general 12 volt 24 volt electronics is how accurate a good quality multimeter can be, but when you're getting into things like testing micro electronics or high frequency equipment AC and stuff definitely a good quality multimeter does help.
02:18 So, when it comes to actually, looking for a multimeter what are you actually looking for and what are you going to get? So, we'll have a quick look here at some of the different things that we've got the most basic they all have sort of similar functions, but this one yeah I think it is the most basic.
02:35 You're going to have generally two different types of multimeters that you'll find auto ranging and manual ranging that is basically just referring to the whatever we're measuring say the voltage or resistance or amps.
02:48 A manual multimeter you need to select an appropriate range that will view on the screen in that particular decimal, so say if you're trying to read 30 kilo ohms on the 200 ohm setting it's not going to be able to be viewed on the screen, so it won't actually show up you generally get something like an OL overload or some other symbol saying that it's not actually reading.
03:10 The best thing with that is you just keep switching through your ranges until you find the right one and auto ranging which is the client that I've got here which is an auto ranging it simply has our symbols for voltage DC AC amps resistance and it will automatically set to the right, range.
03:27 I will note with those if you do have an auto ranging multimeter make sure you give it a couple of even milliseconds, but a second or two when you're getting a reading because they do tend to take a bit of time to actually find that correct range and if you read it too quickly it could be incorrect.
03:45 So, going by what different things it can measure if we have a look at this multimeter that I got here the symbols and stuff on there are quite small, so I will draw them on the whiteboard here just, so you get a good idea.
03:58 First of all, let's just go over some of the basics most multimeters that you have will generally have a power button or they'll have automatic off.
04:08 My main that I use here the Digitech what is it a QM1548 has an on off button, but it also has auto off, so if you leave it for a certain amount of time you won't waste the battery.
04:18 This can be a pro and a con of the amount of times you know with these other ones that where it stays on indefinitely the battery does go flat a lot more often, but with the auto off ones sometimes when you're probing out a connector with quite a few connections and you're sitting there for quite a while probing out you will get to a point where you're probing and there's no continuity you're thinking where's my wire gone and the multimeter is just simply turned off.
04:43 It catches me out quite a bit unfortunately, but it does save quite a bit of battery and I prefer that in the long run.
04:50 So, on our multimeters here you generally will have a dial I think some of the more newer and more advanced might have actual like keys that you can punch in different functions and stuff, but majority of the time you'll find a dial of some sort.
05:05 Sorry about that guys we had some technical difficulties some audio issues, but that should be all resolved now so let's get back into it.
05:13 I think where we were left off you might have just seen I was just talking about the dials on the multimeter itself, so let's just get stuck back into that.
05:23 So, you will have a dial on your multimeter generally that will be split up into its separate sections.
05:29 This one over here we've got a V with a line and a dash.
05:32 V, line, so it's a dash and then little dashes underneath.
05:36 If we keep following around there's another V with a squiggly and continuing around we've got A with the line and dashes and what do we got then? Then we have a waveform.
05:46 Next there's that's line NCV.
05:47 I'll just say quickly line NCV on this is a non-contact voltage it's generally used for AC we won't talk about that much more different probes that you need for it, so I'll skip over that one.
05:59 The next symbol that we've got there we've got a diode symbol and just looks like that.
06:06 That also has a sound wave symbol as well like this.
06:10 Some multimeters will have that separate I think one of the ones I've got here yes, so my SP Tools one that I've got here has a separate position for our diode testing which is the diode symbol and our continuity beep which is the sound wave symbol.
06:28 Then the last symbol we've got on this multimeter is our ohm symbol.
06:33 Going through that our top one is V for voltage, but it is voltage DC, so direct current that's our line with dots and then our squiggly line is alternating current.
06:44 A with the line and dashes is amps and that is DC same symbol as the voltage at the top.
06:51 Some multimeters will do amperage for AC, so this multimeter the Klein Tools one is actually a dedicated clamp meter for AC amps that's the main use of it.
07:03 We won't go into that one too much I just wanted to bring in a auto arranging style and clamp style just to show.
07:09 So, this one I think it's the only one here that does a frequency, so this is things like speed signals like your crank and cam it's generally it's not something you're probably going to use for automotive it will basically tell you the frequency of your signal, so it's just going to register the changes in the waveform and give you back a number of how many hertz per second that that frequency is going at.
07:34 If you really need to use it it will tell you whether you know a sensor signal is working, but it won't necessarily tell you if it's working the way it needs to or for something like a speed crank signal it won't be you know too handy, so I wouldn't go into that one too much more.
07:51 Some multimeters will have it some won't.
07:54 My diode and continuity, so we'll just say cont for that one and diode, so that is our beep test that you generally hear and see people using.
08:02 Continuity simply just means do we have a one point in the other, so what this is actually doing is measuring resistance, but if it is below a certain resistance for my this one over here in particular it is below 30 ohms I'm pretty sure, it will beep out or milli ohms I can't remember exactly, but it's a very low resistance that it will beep out.
08:23 The problem with that is it can sometimes beep out for a circuit that has resistance that we don't want resistance something like an earth, a ground signal, a ground wire.
08:34 If you watch a previous webinar that I did on grounding and good grounding I had a demonstration of that where we had a bad ground and checking continuity between that ground and the good ground it actually beeped out and showed a continuity, but in fact there was too much resistance on that path and was giving us a bad ground, so it's not something that you want to use indefinitely use things like voltage drop which I'll show a bit later, but it is good for just beeping out circuits things like when we're wiring up a harness we can check where one wire is going in a plug or simply diagnosing in our car we can yeah if we have a wire in the engine bay we can quickly find where that goes to our ecu just by touching each side and then finally our ohms or resistance and that is exactly as it sounds can I spell here resist answer yep my handwriting's terrible that says resistance now that's just measuring our ohms or the resistance of a component things like resistors anything from relays the coils we can test wire we definitely want to test if we've got too much resistance in a wire that would cause a voltage drop, but it's everything we have has resistance the air that we're breathing has resistance it has a lot of resistance that's why our current and electricity can't pass through it if you get high enough voltage it will definitely pass through that, but luckily in our automotive we don't really need to worry about it we do with our spark that is one instance where we do have enough voltage to bridge an air gap and bridge that resistance, but we're not going to go into that too deeply today it is multimeter, so let me get back on track, so that gives you an idea of the different symbols that you will see there's a few other different ones I'll go over them when I go over the actual multimeter itself these are the basic ones that you're going to look for in our automotive world we're really going to be just using our voltage dc amps dc and our continuity and resistance they're the main ones, so this one even though I said it is a cheaper multimeter it has all of those does them all properly we have our normal power button, so as I said this one doesn't have a auto off and will stay on indefinitely they'll have a backlight function most of the time my one over here doesn't and also they will sometimes have a hold button basically if you're measuring say amps of something and the amps fluctuates quite a bit you can hit the hold button that'll basically just hold the highest value that that multimeter is going to read can be handy if you're trying to figure out maybe the amp spike of something in particular next thing you're going to notice is we have the leads they're probably the most important next most important part of an actual multimeter it's what we use to actually test our equipment obviously having good leads and good quality leads is definitely going to help and be good make sure you check over your leads whenever you're using them sometimes they can be nicked or the ends can be corroded that's not going to give you good readings we will generally have two to three sometimes four like this one over here separate sockets for those leads to go into we'll always have some sort of common lead which we'll generally put our black into and then we should generally I think all my ones here, so that one's got two again that's mainly used for AC, so we'll focus on these ones in particular basically we've got a couple of symbols above the the sockets to say what we actually use them for this one's got our V for voltage our ohm symbol and milliamp, so underneath here it also says max 200 milliamp fused and over here max 10 amp fused, so when we're measuring amps we are putting our lines in between a current the multimeter is applying a slight amount of resistance to measure the amps and when we're measuring quite low in the milliamps it's generally pretty easy to do and your multimeter can handle it a lot of the time though when you're stepping up to up to above 200 milliamp in this case you will need to use a separate socket sometimes they are fused like this case this one here is not fused internally it actually says under here unfused 10 amp max, but this is saying if you do go over 10 amp you are going to wipe out the circuit inside that multimeter and it's going to be wasted these ones however generally have some sort of resettable fuse or you can actually take the multimeter apart and replace the fuse inside, so most of the time you are going to stay in your voltage or ohms resistance that sort of thing, so we'll keep our multimeter in there I will say it is best it is good habit to keep it in there if you ever do use the 10 amp amp side or any amp part of your multimeter take it out as soon as you're done you might have a situation where you go back to test voltage you're just testing across the ground in an earth if you have it in the amp testing part of your multimeter it will pass current through your leads and if you're touching a just a ground and say a positive of a battery it's going to pass a lot of current through there and that's when you're going to get things like the internal fuse blowing, so it is just best habit to keep your lead in the voltage side and away from that high amp side, so we got the other one over here are the digitech one this has got basically my amp amp sockets are separate both of them we've got milliamp and the 10 amp both on this side socket and my voltage voltage ohms and diode and continuity testing are on the right hand side, so I generally keep it over there unless I am using that amps the client tools one as I said just has the two underneath it's got them labeled here as common and voltage and ohms there is also a symbol in the middle for a ground, so as I said this is for uh ac mainly where the circuit's a bit different um what was the other thing I was gonna say about that uh I'll just say that next actually uh, so yeah we won't go into that one too much we'll just use it as a reference another thing you'll find on multimeters particularly for ac stuff is a cat rating this sp2 one doesn't have it on there yes it does a cat 2 600 volt this one has 500 volt cat cat 3 basically this is referring to something generally in the ac environment that we're not going to be worrying about in dc it's got to do with how close you are to the source of voltage and how much your multimeter would be able to handle, so as I said not something we have to worry about too much in dc pretty much any multimeter you use will be capable of measuring the kinds of things that we're going to need in a automotive environment or you know motorcycles trucks up to 24 volt generally just the dc environment will should be a-okay, so that should just give a bit of an overview over everything on these multimeters and we've got anything else that's a bit unusual this has got a few extra settings on there, but I will show them uh separately I think, so let's actually go through and work out how we use them so, as I said all of these are a manual ranging not auto ranging like the client tools so, basically we have to we make an educated guess as to what voltage resistance or amps we're going to be reading and set our multimeter for that, so if we look in our dc section here we've got if you can't see it on screen I'll just read it out we've got a section for 220 200 and 500 excuse me, so obviously we shouldn't really expect anything uh 200 to 500 volts dc in an automotive world uh maybe with you know you're looking at uh ev vehicles and that type of stuff we're going to keep it in the non-ev section because that's sort of a whole uh different scenario we've got uh as I said 200 500 there you know we're not going to use them we've got 20 now, this is going to show anything below 20 which that's going to cover pretty much anything for us our 12 volt 14 volt if we are going to 24 volt for trucks or maybe camper vans that sort of thing they can even go up to 48 volt we will need to go up to the 200 volt, but in general you should be okay with the 20 if you're measuring something even lower maybe you've got some sort of uh micro electronics you can step that down to two and sorry it does also have here 200 millivolt, so it does go down quite a fair way the millivolt is actually particularly handy if you're looking for voltage drop across wires and I'll show that in a minute let's actually go through and we'll test a few things now just quickly when I when I was talking about cheaper multimeters this was a multimeter I bought for myself personally as a at-home multimeter and I absolutely hate it for one particular reason it is in general a really good multimeter, but there's one thing that just frustrates the all heck out of me and while I'm looking at it there is a little led in here which I didn't mention that's to do with the non -contact voltage when you're testing AC voltage that will light up, so not something we're going to use, but the one function that I really hate, so we know most people will know the continuity test where you want to beep things out when I'm doing it I generally, you know I'll grab my leads go over to a connector or harness and just start beeping out and trying to figure out where the wire is and I'm used to it being fairly quick whereas this has a slight delay and before I knew I had a delay I'd been testing quite a few wires and it took me a while to realize that it was actually the multimeter was too slow for the speed that I was doing for testing those and I did actually have continuity even though the multimeter wasn't saying, so that is something to look out for if you go out buying the cheaper ones they do have some caveats sometimes that might be you know quirks can't live with it they just be aware.
18:03 This SP Tool one's quite a good one it's been the Workshops multimeter for quite a long time, similar functions except this one doesn't have an on off button simply once you turn the dial to one of the functions then it turns on I'll turn the backlight on there so you better see better and it won't turn off until we switch it to the off section, so another thing to be clear of make sure you know if it is a auto off or not and if I go around to my continuity just to give you a demonstration if you can hear that it's much much quicker and you will probably know that notice that you do get a reading on the screen of your resistance, but just the way I was testing I wasn't looking at my multimeter it was off to the side if I had looked I would have noticed a quick flash of numbers.
18:47 Anyway different things about this one this does have down here H, F, E it's just shown as I'll just write it down quickly, so you can see H and a capital F and E this is to do with transistors and measuring transistors like it's something it's to do with transistors I don't know off the top of my head even what it does, but it's not something we're really going to come into play with with our automotive diagnostics might be something that you're into if you're doing microelectronics I've never used it in particular, but it also has here some little holes where you can put transistor legs into and test them I won't go into that one it's probably a bit too advanced for what we're trying to get gather today, so what I am going to show though is our just general voltage measurement I was showing you that one, so we had 220, 200 and so, on this one has now that's the other thing some modulators are different as to where they are on the actual dial and it can take a little while to get acquainted when you've changing between them so, this one is very similar up here I've got 200 milliohms 220, 200 and 600 instead of 500 volt so, I'm just going to test I've got a power pack here putting out 13.8 volts, so I know that's going to be under my 20, so I'm going to set that to 20 again if you have auto arranging that is going to automatically do it for you you just need to find that the the v with the line and little dots underneath, so here I've got my I've got a few little things here set up, but my actual leads I've got my ground here which I'm going to go to my black lead and then red to my red lead and that's going to show me my 13.8 which is exactly what I got on my power pack, so I know that is reading a hundred percent it is always good to test your equipment first find a good known battery that's got plenty of volts in it just chuck your meter across there make sure your meter is actually working I find a lot when the battery starts going flat in your multimeter they generally have say a nine volt battery in behind it when that starts going flat you can start getting weird readings with fluctuations when you have your voltage and that can be kind of confusing and annoying and sometimes it's best just to swap out a battery we had that recently we were testing with this digitech one getting some weird readings and changing the battery solved that and everything was great from then on, so what happens here if I select a different measurement if I go up to the 200 it still works we still have our we've got 13.9, so what it's doing is it's just rounding up decimal places you can see it will shift over slightly, so in our 20 it gives us a two decimal place reading you can get down to 13.85 if that's what we have, so let's swap it over to 200 it's making space, so we can have 200 volts in our screen there and obviously we're showing 13.8 if I go up to 600 it should still read, but then it drops it down again just to give it some extra room so, that is basically that's a bit of the the playoff when it comes to auto arranging to manual it's not really a problem it's just a bit more of a convenience so, that is showing voltage testing the next thing is we'll test resistance, so resistance doesn't matter if it's dc or ac we're checking the resistance of a component and regardless of what you're putting through it it will always have the same resistance I'm just going to wipe off this board to make things a little less cluttered, so I've actually got here just some actual resistors that are found in microelectronics they are much much smaller these days, but I didn't want to bring something that you can barely see and all we need to do is put our leads across it first thing though before you go measuring resistance I highly recommend testing your leads, so as I was saying everything has resistance including our leads of our actual multimeter a good quality pair of leads I tested these clan ones before have little to no resistance that registers my digitech one over here registers about I think it was 0.03 ohms of resistance and I haven't I don't think I've tested these ones before, so I need to find ohms again down here I'm going to go down to the lowest setting on this which is 200 ohms a lot of them yeah another around the 200 ohm mark and we just simply put our leads together and you can see a number come up there turn the screen back on and we're getting 0.5 ohms of resistance, so we just need to keep that into account when we're measuring the resistance of something in particular it is a very low number, but if we are measuring something with only 0.1 0.2 ohms of resistance it's going to show us you know 0.6 0.7 ohms on our multimeter, so it's just worth keeping that in mind and this light continues to turn off on me it's kind of annoying in fact I'm going to just use my digitech one here from here on out because I know it's reliable usually let's bring this one into play and, so our resistance on this one is up the top here, so as I said there's no it's still got an on off button it does have an auto off now this one doesn't actually have a backlight that's okay I think you guys can see that pretty well from my screen and our range for the resistance goes 200, 2k so 2000 to 20k 200k 2m or 2 million and 20m for 20 oh sorry not million mega ohm, so that is 2 kilo ohm 20 kilo ohm 200 kilo ohm 2 mega ohm 20 mega ohm and we're not going to be reading anything quite that high I actually can't remember what resistance resistors I grabbed, so that is a good surprise for everyone, so if we've got a situation where we don't actually know what the resistance is just start at the very lowest setting and we want to put our leads across it now when you're measuring something you want to really make sure that it's not touching anything else because that will sometimes play into account particularly things like even your fingers can add a bit of resistance touching that, so we're not actually getting a reading, so this one just gives a one and a dot that is its kind of overload or out of range function, so this is telling me that it can't read what is there if I bump it up to 2k still nothing 20k and we're finally getting a reading so, that's telling me we've got 4.71 kilo ohms, so that's obviously over our range of 2k 2 kilo ohm that's why we weren't getting anything on those lower two readings, but in the 20k that's perfectly in our range and we get out for what I say 4.7 kilo ohm if I turn this over 4.7 written on that packet, so I got that correct, so I know that that is measuring the resistance quite well as I did say measuring the resistance of our leads I mentioned okay, so it wasn't 0.0 it's actually 0 .3 ohms and let's see what this one here is again the 200 is not reading 2k and now we're getting a reading on that 2k and that's showing 0.511, so at in the k readings we're trying to measure over uh up to 2 , 000 kilo ohms uh 2 kilo ohms sorry 2, 000 ohms so, that's why we've got our decimal all the way up the front here we're currently reading under 1, 000 or 1 kilo ohm we've only got half a kilo ohm, but that's over our 200 hence the why we have to go to that range, so these should be a 510 or 500 and that is a 510 ohm resistor uh, so that's yeah that's measuring resistance quite easy it does come in handy for things like relays you can check across the coil contacts just got a simple relay here and I'm just going find my 85 and 86 if I go across those contacts with my leads I get a resistance this one's showing 99 point round point well anywhere between it's fluctuating quite a bit we'll say 0 .3 ohms and that's telling me that there is a good connection there we can look up the actual data sheet for these relays or any component in particular and it should tell you a actual ohm reading and what you should expect particularly good when you're testing things like sensors if you have a data sheet of a sensor say a temperature sensor that relies on a resistive reading you can see what it should what resistance it should have at a certain temperature correspond that with your data sheet and see that it is working appropriately you can even use that to map your own calibration sheet from a sensor that you're unaware of you do have to be able to control the temperature quite well, but you can basically just go through up in 10 degree increments and measure the resistance pop that into say an ecu and then you'll get a nice calibration curve for that particular sensor the other things that we have on here, so we've got our resistance amp is the next one before I get into reading amps let's actually go through some just some testing that you can use with your the voltage and resistance sections of your multimeter particularly the continuity as I mentioned before that's got a good beat you can get situations we have continually showing, but it isn't actually probably a zero resistance circuit or a very low resistance circuit that we want something like as I mentioned in previous webinars for the grounding a ground that actually wasn't good had high well not high high resistance but enough resistance that was causing issues with our lights the multimeter was buzzing out, but it did show some small resistance and a good place to show that I don't think I actually have anything here to show that my example that I've got here when we're when we're testing fuses in particular one thing that people generally go to is simply testing for voltage at our fuses getting say a tesla checking across both can actually run into some issues with that and, so what I've got here just a simple I've got a relay with a fuse in it just to help hold it I'm just going to put my 12 volt on one side, so if we were testing our fuses looking for a blown fuse we would generally just go through check either side of our fuse and see if we've got 12 volt if we don't if we find that one doesn't have 12 volt on both sides we'll generally just say that that is the busted one and replace it, so let's just go through that here we've got ground on our it's going into my ground lead here for my power bank and we're going to spin my dial around to our 20 glue in that the 13.8 volt range and using that I can just probe one side of my fuse and there's a little bit of thing with my particular multimeter here sometimes it doesn't show the decimal I have to just go back and forth and there we go now it's come up, so that's showing my 13.75 that's just saying we've got about 0.05 voltage drop somewhere in the circuit that's not really what we're looking at the moment we just want to see we've got 13 volts there on the other side I've got 13.7 volts there perfect that that fuse should be just fine, but contrary to what that actually measured if I take this out it might be pretty hard to see, but it is actually black and quite burnt out we've got a situation where we've got a big bank of fuses and we don't really want to go through pulling out each one we might just go through and use that voltage test, but that does cause issues where even if I use my light here and I put my power across this fuse I'll put it through not the fuse just so, you can see that it does actually work if I put it across that fuse nothing it's not working even though we showed 12 volt on both sides the reason for that is because it's managed to strategically burn this one out where it was a very slow burn it was just above its 5 amp rating and it's managed to somewhat hold on a little bit inside the main circuit is blown and it doesn't obviously, conduct current through it, but it does show a small very small continuity sorry not voltage across it as soon as we try and apply a load to it though obviously everything shuts down and now if I try and measure it it would have completely blown that and we wouldn't get that 12 volt across, but the reason I'm bringing this up is the best way to check our fuses is just that simple continuity check, so if we go around here to my sound wave and my diode because it's in both of these we will get our beep and this will show no beep and it does actually show we've got some resistance there, so there is still somewhat of a circuit, but there's too much resistance for it to be a good continuous circuit and in this case yeah it's not going to work as a fuse should if we check an actual proper fuse that I've got here that I know isn't blown we do get continuity across those tags and as you can see we're only showing that 0.002 ohms which that should be that is the resistance of my leads, so that is a good fuse and obviously a bad fuse.
31:22 Also as I showed before you can check the resistance of coils of a relay if I go back to my we'll say what was it was about 98 ohms, so I expect this one to be pretty similar, so I'll just go across my leads here and I've actually got nothing on there at all even if I go all the way up to my highest resistance setting there's absolutely no resistance by oh sorry there's a lot of resistance it's the other way there's too much resistance between these pins and that's because I actually went inside and cut the circuit, so there is an air gap in between and basically that air gap is too much resistance for our voltage to cross that relay won't actually work anymore I have busted it for good, but it was just to show you guys that it's another way of testing things like relays testing for our continuity sorry it wouldn't be continuity across that the resistance across those contacts the switching side or coil will show us whether we're getting a good resistance like in our good relay around 98 ohms or overload over range something that's too much resistance for our multimeter to check which is our air resistance our air gap and that signifies that it is a faulty relay.
32:38 So, we've gone over checking basic voltage the resistance of multiple things continuity and why using continuity for checking a fuse is a really good way you can also use voltage drop across a fuse is a really good way for checking for voltage draws current draws in your car I've got a separate webinar that goes over that a bit deeper and shows a good example so, you can basically just probe your fuse left to right as long as it's a good fuse probe on either side with your ground and power if you do get a voltage drop across it, so it shows some voltage across your fuse you look up there's a chart that'll show what particular fuse the resistance that'll tell you how many amps you're actually drawing over that fuse, so that's another good test that you can do.
33:26 So, talking about voltage drop what I've got here I've got a big roll of wire and essentially I've just stripped off a bit at the end on one side I'm going to connect my power straight into that wire and then the other side of my, what have I got here, sorry no, I'm going to put my power onto the light, so that should just be a working circuit yep but I'm going to interrupt my switch with our long roll of wire, so it's going to go in one side and I've actually already got a lead here this is going to go on the other side and it still works that is completely normal that's what I was expecting and that is why voltage drop can be an issue that can be hard to diagnose or find.
34:17 Basically, we're going to be we should be in the maybe in the millivolts we'll start off in millivolts just to see what we get note with a lot of multimeters this isn't a super expensive one you do get a bit of fluctuation in millivolts just from waving around in the air, but when we actually put across if I want to go across my leads here, so we'll actually go measure millivolts across this roll of wire as we got current going through and it is above millivolts, so we're going to go into the voltage now, another thing to note we have got a negative sign here that is simply saying my leads are the wrong way around if you swap leads I'll just show you quickly if I put my negative on the power and power on the negative in my 2412 volt it'll simply read my voltage, but in a negative because it's seeing it going the opposite way you're still seeing a voltage, but good practice just to keep your leads the right way around and it will get rid of that negative sign, so back to my little test here we'll go back down to two volts I think that'll be the right one and if I chuck that between my lead there turn my light on with one hand do everything with multiple hands and go across here I'm showing 0.793 volts and that is purely across this roll of wire so I'm dropping almost a volt across that roll of wire and that's important because when we have things like a fuel pump in the back of our car the more amps that we put through the resistance of that wire the more voltage drop we're actually going to get, so if you imagine a really long wire at the back to the back of your car for your fuel pump if it's not appropriately rated wire has quite a bit of resistance for that length and you push the amps of a fuel pump through it you will get more voltage drop and what that means is the voltage that actually gets to your fuel pump or the light in this case will be considerably less than what the fuel pump needs and this can cause issues in the long run, but something like a light really doesn't matter as you saw I don't think it even barely changes the difference if I just quickly swap that over there's no real visible difference as far as the brightness maybe a little bit brighter when I don't have that in there, but for things that are sensitive to voltage fluctuations things that really need the most voltage as possible like a fuel pump we definitely want to rectify any voltage drop situations that we can.
36:38 To remedy that the basic solution is to just up the size of your wire the larger the wire is the less resistance it's going to have, so over a longer distance you will get less voltage drop.
36:49 How we going for time? Pretty good I've still got a few to talk about, but if you've got any questions start checking them in now and we'll get to them soon.
37:00 So, I'll just go over a few things on this multimeter and then we'll get into amp draw and checking for amps, so you might have noticed this one has quite a few more things going on around it the main ones are I've got LX and CX they are for testing capacitors the capacitance and also inductance not something that we're really going to worry about in the automotive and just general electrical DC it is something that when you're getting down to microelectronics sometimes you might be using the capacitive checking for certain things I can't even think of the top of my head what you'd be looking for, but inductance as well not something you're really going to worry about you might be checking inductance of a relay coil, but I can't even think of why you might be doing that, so yeah I'm not going to go into them too deep, but this multimeter does have that capability if needed I particularly bought this one for yeah being able to measure those things for microelectronics, but it is also really good for just general DC and even AC work it does have, so I've got my voltage with a line and dots and voltage with a curly dash that's my AC.