How to Use Multimeter Readings for Electrical Troubleshooting | TPC Training

Hello everyone and welcome to today's public webinar for tpc

training

titled Understanding Multimeter Readings for Electrical Troubleshooting. Today we will spend about 45 minutes together to really understand the different

readings

we can get and what they mean when it comes to testing

electrical

circuits with a

multimeter

my name is ryan smith I am a tpc trained instructor and also a tpc trained product manager. I'm going to explain some of these

multimeter

readings

to you today here, so before this session I want to make sure to let everyone know that this session is being recorded, so if any of you or your colleagues missed this session, feel free to come back view it on our website and we will send you an email with that link within two or three business days from this date. webinar and you will also receive a pdf of these slides.

A second thing I want to let everyone know is that we will be accepting questions and answers during this session, so this is a live event right now and what that means is that I'm just not a pre-recorded voice, you can actually interact with me , so I really hope you go to the q tab in your dashboard here for this session and type in and finally we're going to I'll be going into some details about my table here to take a look at some meters and some readings from different devices, so which in doing so I want to make sure that you make me as big as possible when I stop sharing this screen here and do Make sure my video is full screen then you should be good to go without further ado what are we going to talk about today ?

So, the first thing we need to do is solve

electrical

problems, this meter here will be the one we are going to use. Use it here to understand multimeter readings and this really is a multimeter for a good reason, it can measure multiple different things, the three that interest us the most in this session and for almost any electrical circuit are current voltage and resistance, so So our first talking point today is to make sure that we understand what current voltage and resistance is in a really quick way. Now, this is not the basis of the electrical webinar, however, you need to know what those three are in quite some depth to understand what. you're using your multimeter, so we're going to break down the testing of each, understand ohm readings, start with ohms, and then move on to understanding and measuring. voltage in electrical problem solving in different ways and that will be in a simulated voltage environment and then we are going to measure amp readings as well so let's start with current so what is current?

So current really is the easiest thing about electricity. to understand well and that is the flow of electrons flowing in a circuit, you could say: well, I can't see the electrons flowing and you're right, you can't see them in their microscopic format flowing, but you can see the electrons flowing around you. every day if you look at the room you are in now and look at the lights shining in your head, if you see a light shining that means there are electrons flowing through that light producing that light for you, if you hear the humming of your air conditioner, the hum of your heater, that noise you are hearing indicates that current is flowing, so the first step of any good electrical

troubleshooting

process is to listen and look properly, use your eyes and ears to really see.

What are some of the problems. what you are seeing well are lights flashing, that means current is flowing to that light, it is a motor running, the three phase motor hums, that means current has reached that motor, however the other two here, voltage and resistance, they're not so easy to see here, so that's really where we need this meter because this meter can tell us a story that we can't see and that we can't hear with our own human senses and that's where it really comes into play. become extremely valuable, in fact, two most important tools I always like to say that for any electrical troubleshooter, the two most important tools you can have are not a hammer or a screwdriver.

The number one tool is a multimeter, a very well rated multimeter, and the second tool you can have is you. You may not think it's a tool, but it is and it's schematics, so if you have a meter and then you have a high-quality up-to-date schematic, you can do any type of electrical

troubleshooting

work you need. We're really going to focus just on the multimeter readings again today. There's a lot of detail to go into here, but we'll just give you a quick refresher in this webinar. Let's talk about voltage. Voltage is really that potential difference.

It doesn't have to do with the electrons that flow, but with the energy that those electrons have when they flow, whether they have a really high potential or they have a low potential and then what is the difference between one point and another, so the most trap The big thing we fall into is measurement. with a meter in just one place and saying: what's the voltage right there? What is the voltage right there? That's not a good way to understand voltage, it's actually what is the voltage difference between here and here, so let's talk about that and measure those readings and then finally resistance, so resistance is the opposition to the current that flows to the right and is measured in ohms, which is an upside-down horseshoe symbol and we're going to talk about that and it's really going to be up to us.

I understand what zero and ohms mean versus an old-fashioned reading on an ohmmeter, what does it mean? that, so let's talk about that too, okay, so let's start talking about ohm readings and in doing so, I'm going to leave my part of my screen, so it should appear larger for you. Now go ahead and make sure it's as big as possible on your computer or monitor screen and now I'm going to change my camera angle to my table camera, so here's my table. and you can see the meter here on my table, so what we're going to talk about now is ohms first, so we'll start with ohms because ohms are the best to measure when there's no power, in fact, even better.

You should only measure ohms when you are completely disconnected from a circuit. It's much better, but you're testing ohms on a device that's been completely removed from a circuit on a table like this, that's the best way to measure ohms on something, whether it's a fuse or a control device like a button or switch. or a relay or any other type of device that even includes a three phase motor, take it out of the circuit and place it on a workbench or table, that is the best way to test ohms. So you can see here, this is a multimeter that we are using.

It has ncv, which is a non-contact voltage mode. You can measure amps in AC, so the wavy line is AC and the straight line is DC. We have voltage with the wavy line. that's AC voltage, we got DC with the straight line voltage and then we have a bunch of different modes for the resistance so you can see the ohms, the upside down horseshoe symbol here and this can also measure diode capacitors and can give us an indication. finally we can measure the frequency in hertz and if we have a thermocouple connected to the red and black ports here we can measure the temperature, so what we are going to do now is convert this to ohms, so it's time to measure the temperature. and the first thing I'm going to set is to give us audio, so I set it on the little sound icon to give us audio whenever there's resistance, but the first thing we see here is okay.

Who can tell me what is ol? Who can break the myth? What does ol mean? Well, it depends on there being an agreed upon industry term for ol and that's open line, open line, that's really the best way to understand what ol means. Open line. people get caught up in understanding um ol as being overloaded or over limits, that's a misconception here, it's definitely o l as an open line, so that means something open and now what does open mean? It's going to be a huge thing to understand when you get to understand what the open ohms readings are giving us, so it's telling us that between this red wire and this black wire it's open and that really to us means there's air or a really very high resistance between. the red wire and the black wire, which gives us the reading of ol so that really tells us that if we see ol it doesn't mean there is no resistance, that's something we get caught up in thinking that ol means there is no resistance ol actually means so much resistance between red and black that the little power supply in this meter An electron cannot be passed from the red lead to the black lead and vice versa if there is so much resistance that we have exceeded 99999 in this meter so it will just tell us that's really what it means, okay, it means very high amounts. of resistance, okay, now, if I touch these wires together, it will be very easy to go from one to the other; in fact there is nothing between us so it will give me a low ohms reading and beep, you should be able to hear it. that beeping through my headphones, if not, it's beeping at me and we're getting pretty close to zero ohms, as close to zero as we can get, we're playing these two together, so when we're not playing red to black, we're what To call non-continuous or not having continuity, that's the term we tend to use, that there is no connection between where we put the red wire and where we put the black wire.

This can be measured based on a device or within a circuit, so I'm going to measure some devices here on the table like this red lamp here where we can measure whether it's working properly or not. I'll take a look at a button on the side of the control device. We're going to take a look at a relay, we're going to understand how to do ohm readings on this relay and finally I'm going to do a quick ohm reading on this motor starter. Okay, so let's start with this light, so what we're going to do is Let's try this light, so this light, this light is something that should work for us, should illuminate us, so anything that should work for us It should have some resistance in ohms, it shouldn't. zero, there should be some kind of resistance amount, so what I'm going to do here is test from the left side to the right side of this light and see what we get correctly and this has given me that we see that 27.5 ohms, so that it's really a resistance amount here that this thing is really good and it's doing some work.

You can do some work for us now if we turn off this light, let's say it wasn't shining on the panel it was on. and we put it in and we crossed it and we got it right, that means the filament inside this has burned out or maybe the bulb is missing from this thing, so basically this is not working like it should and now I identified it with this bulb instead from, say, a wire on the panel or a relay on the panel, it was actually this light that gave us the problem, okay, let's talk about something that should have virtually no resistance or almost all resistance. and these are what we call control devices so this light is what we call charging it will do some work for us it is called charging while this button is what we call control device and this is what we want to know how to Try also with control devices like buttons, switches and relays, we have to get used to the term um open or closed, so we really have to understand what that is and it takes some practice and I recommend that you continue to practice the terms. normally open and normally closed, and this is what we mean by this: it allows current to pass or it does not allow current to pass, in other words, it has all the resistance or it is passing through this thing or it has no resistance passing for this thing, it's just one step and that will give us close to zero ohms if it works correctly, so what state is this selector switch in right now?

Is this selector switch not allowing current to flow or is it allowing current to flow? You can say it? Well, I can. I can't tell, and that's really where this meter comes in, so let's test the selector switch to see if we're allowing current to pass through or not, so let's say the lights it turns on aren't coming on correctly. To find out if the switch is in the right position, we turn it like this and you can see the contacts on the back of this thing and we go from left to right again and we get to the right, so what does that mean it's open? that means this is not allowing current to go to wherever it's plugged in right now, so let's go ahead and change it to its other position, there it goes and now I'm going to turn it over and test it again and we're pretty good. close to zero ohms there we go, that means this is the closed position of the switch and if maybe we mislabeled this thing maybe we didn't label it on our magic marker in the field like we should have or whatever label we chose with this buddy, so this is a good way to know what happens if in botheither way it measured, well, or both ways it measured zero.

Now we know something is wrong with the switch, so that's a good way to measure a control device, whether it's at zero ohms or not. is it all ohms or okay let's talk about relays next so this is a control relay that has the top of the relay which is basically where all the brains of this relay are and then it has the base where you can actually connect the wires, this relay has two main parts, it has a coil and a contact, and the interesting thing is that a relay combines a load like this light with a control device like this switch. and it has both the inside and the inside of this little package, so it has a charge inside in the form of a coil that can create a magnetic field and push and pull contacts and then it has those contacts, so I'm going to take it out of The base I just took it out of its base, so we just see these pins at the bottom that correspond to the numbers on the base.

Okay, both parts of this, I'm going to zoom in so you can see it there. come on so the two pins on this that correspond to the coil which is the loading part of this again I need to be careful not to lose my microphone are a1 and a2 which are just off center and you can see that when I put the cables on a1 and a2, we have about 70.7 ohms, so what that means is that this coil that is going to push and pull these contacts in the field is working properly, it's not burnt out at all right now, I know you can't see .

These are really small numbers, but if we look next to this, we can see what all the pins connect to right now, so basically this connects from 9 to this one that says terminal 9 to terminal 11. They are normally open and then terminal 8 to terminal 11 are normally closed so here's terminal 11 here's okay and then here's terminal 9. just two away and we can see it's ol' so it's open and that's okay , then we go 1 next to from 8 to 11 and that is normally normally closed and we can see that it is closed right now. What if we wanted to ensure that they can correctly switch from open to closed or from closed to open when we energize the relay?

I can't put a wire on this thing without giving myself an electric shock or having a circuit here, but what we can do is simulate this thing by pushing up this little thing on this relay or is there a way to basically simulate the energized state on different relays , They come in different shapes and sizes. but this is the way to do it on this relay and we go back and try 8 or 9 to 11 and 9 to 11 used to be old now it's giving us close to zero so it was closed and then this one was used. it was zero and now it's fine so they did their switching correctly every time it was energized so we actually verify that this relay is working fine now, if we ever measure from a1 to a2 and get the correct result that could mean that We burned the Roll This Thing up and we have to go right, so I just want to make sure you can still hear me.

Please let me know if you can still hear me again if this headset might be shutting down. I'll have to get a new one for you for the rest of the session okay okay thanks guys um yeah there's a good sized audience here so I appreciate it guys now the next thing I want to try for you is this. motor starter here and this motor starter is an IEC style motor starter and what it does well is start a motor properly, but really what this thing can do is it has a lot of auxiliary uses so what we see is that the three phases of a motor come in here and then come out the bottom to start that motor and what that means is that from top to bottom they will connect to the motor and start that motor only when this contact is pushed here, okay ? but what makes that approach correctly I can press the button to do it or I can make it happen automatically by sending a magnetic field, an electrical signal to this coil here to produce a magnetic field that attracts this automatically, so one thing What we can do with this motor starter is to make sure that l1 to t1 down here gives us zero zero and zero and then we can press this here to the right and then measure zero or sorry o l o l and o l to start with the right o l o l o l and then We press this and then we get zero zero and zero, so that's actually a good way to make sure that the contactor part, which is the part that connects the three phases of a motor, is off while we start the motor.

The next thing we can do is test. this overload contact down here, so this thing will send a signal to a control circuit to start a motor or, sorry, stop the motor when it gets overloaded and what we mean by overload is it's just using too much current from the what is it. rated for right, so if we open this little glass access panel here, wow, we can see that these two contacts here are normally closed right now, which means that if we are in normal operation, these should be closed, let's test them and there we go, we are getting zero ohms, that means we are closed.

Okay, now if I simulate the motor overload that presses this little tab here to simulate that now comes in, this should measure ol and there it is, that means this. The normally closed contact set with the overload works fine, so we can press the blue button that I just pressed and we reset it so it works normally great. Now be careful when resetting these overloads on the panel, they are usually around three phase, 480 volts or 208 circuits so you need to be fully equipped if you ever want to reset these overloads. I know it seems, uh, I know it seems a little crazy to have to equip everything with your Arclash gear, but you'll be very glad you can do it.

What would I do if something bad happened? Okay, so that's all I wanted to show you on different resistance measurements of different devices, so ohms again ol means all resistance and zero means we're closed or we have very low resistance, so that's really what we're talking about. of ohm readings. Now I really want to move on to voltage readings using this meter and by doing so things have probably changed for you because now you can see me. Now, what I'm going to do is share. my screen does, so I have a big question. I'll be able to answer them after the fact as well, but you can see in this motor starter here that we have l1 to t1, l2 to t2 and l3 to t3 are the shapes. to test with the meter top to bottom top to bottom top to bottom great question and we'll be able to answer more at the end.

Okay, now let's talk about the voltage, that potential difference, so our goal is to really understand what the potential is. measured on this black wire and then the potential of the electrons that are measured on this red wire and what is the difference between them, so my first myth and you may have remembered it from the description of this class is zero voltage. it means our system is de-energized if we measure zero volts on the panel, does that mean our system is dead and we can start working and we are safe? and the answer is not at all correct, not necessarily correct, so the voltage is exactly zero.

Zero voltage means there is zero potential difference between the two points that you correctly chose, so if you just put the red wire here and measure something on a panel, guess what has nothing to do with this black wire, so you're going to measure . zero or if you measured the red wire and the black wire on the same phase you didn't realize it was the same phase, say the orange, brown or yellow phase of a 480 volt circuit if it is the same color as the same color, you will get zero voltage potential difference, so even if you are as active as possible and your rack gets badly hurt or dies inside the cabinet, it will still measure zero volts and a meter will measure zero. volts, if it's on the wrong setting, I'm sure we're all guilty of this from time to time, if I changed it to DC voltage instead of AC voltage and went into a cabinet to measure, it won't give me anything but zeros because I'm on the wrong configuration so keep that in mind too so now I'm going to share my screen with you in a simulated environment so now things should have changed so make sure you can see this screen in big, so be sure. you figure things out, I'll just give you a second to move the screens.

I know things move a lot. I want to see a lot of fun things before I end the day. Okay, now this is the voltage reading section. and let's say this is the panel we're dealing with again, we're assuming we're all equipped with our arc flash protection equipment, okay, we have gloves with the proper voltage and we have a meter with the proper voltage. What voltage are we dealing with here from this circuit? You can see again in the circuit diagram. The second most useful tool that we have, we have 115 volts AC for this circuit, so what we're going to use is our baseline to know well, what should the potential difference be in this circuit?

So here's my meter. I'm going to change it here. Does N1 know if it will be AC ​​or DC? It will be CA because we see here just CA, so I am. Let's change it to AC, the wavy line and we have the red and black wires here, so this black wire it's a good idea to use ground as a reference for the low potential, so let's put that green to ground and then This red, let's drag it to the line. Now we're looking at 115. Now what happens if I put that red on its own? We would measure zero volts because there is nothing to compare it to, so you always have to compare one. point to point or what if I do line to line correctly, this thing will give us zero volts because again it doesn't matter, the zero voltage reading doesn't matter and it doesn't say it's de-energized if we're measuring from the same line to the same line in this case, okay, so you have to be careful not to do that and be careful, so let's go from line to ground, there we go and then let's move this thing. let's go here still at 115, that means we have a high potential where the red wire is and we've gone down to a low potential, so what does a voltage difference really mean?

This is what I like to tell people when we read a voltage potential. between the two wires we can tell ourselves that possibly two things are happening between those two wires, or some work is being done between the two wires, in other words the circuit is working properly and let's say the lights come on. on or whatever, that's one thing or there's an open circuit between the two wires causing that full voltage where we're dropping all the way and now we're dead on the other side, so in other words a full voltage reading means that the circuit is working or the circuit is not working properly, so that doesn't really help us reduce it much, but when you move that high potential wire around a circuit and see where the voltage goes from 115 to zero all of a sudden, where maybe you didn't expect it to happen. or I didn't think I should do it according to the schematic, that's where we find our place in electrical troubleshooting so we can go right 115.

We'll do our first check, which is 115 here and then 115 here on the other side of this fuse. so the load side of this fuse is also 115 volts. We have just shown that the potential of the electrons flowing through this fuse is still high even after the fuse. Guess what that means? The fuse is in good condition. The fuse is working as it should. At least we can say that with a high degree of certainty, so we'll follow these now let me go to one of these buttons here, okay, I'll drag this over to the input side of one of these green buttons again, press this button. and these lights come on, you see how they came on and you press the off button and they go off and on, so we're looking at 115 volts right here on the other side of this button, that's what the voltage should be like.

I expect to read on the other side of this button if it will go to zero or stay at 115. Well, this green button is a normally open button, meaning it will only allow current to pass through when you press it correctly to start. switch, that means if there is a high potential inside or incoming side, the line side of this button, the other side will be zero or should be zero, let's find out it is zero, that means this button is like this . So far it looks pretty good, but if I press the button what should happen?

We should energize that other side and be able to see, excuse me, we're getting that total voltage potential difference every now and then is 114.8, so within a margin of error of that 115. great, turn it off and it should come back on. zero, there it is, so that's one way to look at it and now again we could take that voltage potential up to the light, which is really a fun way to use voltage as we go around a circuit at different points and see where the voltage goes from the total voltage down to zero or if you start getting some voltagesstrangers somewhere between 115 and zero, in this case, you know what that could mean. that now we have bad wiring in our circuit that is causing some voltages to get trapped in there, especially when we have a bad neutral on the neutral side, we end up getting really strange voltages when we go through the neutral, so if we were going to measure ohms here, There is one thing that we must always keep in mind: volts, which you practically have to measure in a live circuit, because volts are the energization of the electrons, so we have to be prepared, we have to do this in the ohms of the circuit Live measurements should never be done on a live circuit, in fact if I tried to measure ohms now I wouldn't be able to get any good readings, of course I would leave, the meter allows you to do whatever you want. with it, but a you wouldn't get good readings which would be inaccurate and b since the meter is not rated to measure live voltage you could actually damage or destroy the meter or worse yet, hurt yourself in the process by causing an arc flash or some other serious injury, so be careful when measuring resistance within a panel and if you must measure within a panel, make sure everything is completely de-energized within that panel.

Okay, the next thing I'm going to show you, sorry, is this meter. Here we're going to talk about amps next, that's the third of the three multimeter measurement steps here and essentially I'm just going to use this wire to simulate a wire. Here this meter is measuring, it has a clamp here and this. The clamp really is the amplifier clamp, I'm sure we're all aware of that and this measures um amps flowing correctly now, how did that happen? How is it possible that we can measure the resistance flowing through this clamp? It's really quite surprising that it alternates. current power AC power and current when it flows in a wire like this it produces a magnetic field that rotates around that wire at all times while it is flowing and when it is not flowing that magnetic field disappears so if we can measure the strength of the magnetic field around this wire when alternating current flows in it, guess what we can measure how much current flows in it just by letting this thing crunch the numbers and tell us how much current flows so you can basically clamp a wire around it, make sure it's somewhere near the middle of this clamp, it usually doesn't matter, they're not too sensitive about it and there's a little chip here, it's inside this clamp and this is basically a little magnetic field detector that will tell us and detect. how much magnetic field it's detecting and then tell us how many amps it's measuring for DC if we're going to measure direct current, that's where we're actually going to have to install the meter in the circuit so that the current actually hits one. side of the meter and comes out the other side in the DC circuit, so it's not that easy to measure using magnetic fields in a DC circuit, but it is possible to measure current in that DC circuit, so that's really one way to do it. and you can see it in this schematic, I mean, there are so many things you can try in just a simple circuit with two light bulbs, right?

You have to test the relay, this relay r1 and make sure the coil and contacts are good, you know? dozens, if not hundreds, of control devices that are open or closed at any given time to run your motors in your facility or to run your devices in your facility, there is a lot to test, but if you just follow step by step the scheme by keeping one wire in one place and the red wire in the other places, you can really get where you want to go quickly, so that's all I wanted to talk to you about, so let me summarize here, which sets this up for us, Leave me alone.

Recapping this right now first and that's zero ohms, right, it means we're closed from point a to point b, there's a solid metal connection, so we can never get zero ohms, by the way, there's no such thing as zero ohms, um, if you can. find a substance or a piece of anything, a piece of metal or anything that has zero ohms, absolutely zero, you could win the Nobel Prize because we're testing with these superconductors and everything else, so your meter probably won't measure a perfect zero, but it measures maybe less than five ohms or you know one ohm two ohms half an ohm dot one ohm that's a closed circuit that's where we have basically solid metal, let's say copper or aluminum or steel between point a and point b oh well there's a big discussion going on the line about what ol' line means all I've seen is an open line it really depends on the manufacturer they all give different descriptions in their meter manuals and then it basically means high ohms high amount of resistance there and uh this should be done at the level of the test component on a table, right for the ohm readings, now for the voltage reading again, when and where it should be in a live circuit live on the panel at zero field volts means there is zero potential difference doesn't mean there is no power in that cabinet so be careful where you are measuring your voltage, that's really where it comes up, excuse me, this is a qualified person where you know where to measure based on the reading the schematic, you know what the schematic is.

Tell you that you know where to measure and what the readings will be when you measure them. The thing you always want to make sure when measuring voltage with a meter is that you know what you're going to get before you touch them. drives down it's never really a good idea to say I wonder what I'm going to get here and go in and maybe beat your meter ratings and just blow up the thing so you always know what you're supposed to get and if your meter is rated correctly for that job does reading a full voltage mean we are active?

Not necessarily either, I mean it could mean that the circuit is working correctly and is fully active and operational, but it could also mean that something is wrong and where is the voltage. is dropped somewhere in that circuit, we have to do all the electric arc ppe also when we apply voltage, while the ohms we can do it in our street near or whatever on a table, as long as we are completely disconnected from the circuit and finally amps we use the amp clamp which can do the magic of magnetic fields makes measuring amps on a cable very easy.

One thing to be careful of with an amp clamp is if you have a live wire running through the amp clamp and another wire. with the current going in the opposite direction passing through the amperage clamp at the same time, you will get zero amps on this meter because it is measuring one magnetic field in one direction and the other in the other, say the hot and the neutral. We are putting them in the same place, they will cancel each other out, so be careful with that too, now is the time to ask questions, so let's see what we have.

We definitely have a good chat on the chat line, unfortunately not. I won't be able to follow all the chat messages, but let's see what kind of questions we have here. Excuse me, so, yes, this meter, so what model is it? This is the proster meter we are using here for our classroom demonstration. I have cm 6000 pro here, so cm 6000 pro um yeah, sorry, when the volume cut off early, I hope you heard me, uh towards the end of the session here, um, yeah, will it be available? Will it be available online later? I absolutely will be.

I'll put it there, our company will put it there about two business days after this session ends. Does it matter if red goes to the ground and black goes to the head? That's a great question, so in the case of alternating current, generally what happens inside a wire is that electrons just go back and forth, they vibrate back and forth, so black versus red is highly recommended that you always have the black be on the low potential or ground side and the red be on the line side because that will give you the best readings um usually sorry yeah sorry um for Usually the red vs black debate really happens when you are in DC, where the current only flows inward. in one direction and it doesn't go back and forth where you could actually get negative or incorrect readings if you change them, but generally you should still be able to get understandable readings, but you want to make sure that best practices are put in black. for low potential and red to higher potential um this presentation will be available yes, yes, yes, sometimes there are just so many great questions here: why would we need to run two cables at the same time through an amplifier clamp and that's cool.

Sometimes we just do it without realizing it because there are so many wires inside or we clamp a wire correctly and don't realize that the hot and neutral are on that same wire, which is why when you put an amp clamp around a wire that has both hot and neutral, you're not going to get anything, you say, oh, you know, this laptop cable is not giving me anything and that's because that's what it means, what does true rms mean? Great question and what is the voltage reading on a fuse, does it mean the fuse is bad?

Good question, so the best, I suppose, foolproof or foolproof way to verify that a fuse is good is to be able to safely remove it from the system when it is completely de-energized. take it out and test it on the table with ohms, so if you go from one side of the fuse to the other, the best way to 100% verify that the fuse is working properly is if you test it and it gets pretty close to zero ohms. true it is allowing current to pass through it is closed if you test through a fuse and it pops out that means the fuse is bad that is the best way to check it now using voltage testing can allow you to actually see if that It's happening because we're live. live live and then we go to the other side of the fuse and it's dead so we go from 115 and then on the other side of the fuse we go to zero, although this should be working correctly, that's what starts telling you that it's okay, something is happening.

That fuse is really where the voltage can start to help us quickly focus on where to look and what to check, always check the component you are about to replace with ohms before throwing it away and before replacing it just to verify proper usage. What we're talking about today, what does true effective value mean? Great question then, the voltage on an alternating current actually goes up and down 60 times a second in the US or 50 times a second 50 hertz in the UK and other countries going up and down. 60 times per second, that means the voltage reading on an AC circuit is going to go up and down 60 times per second, not necessarily correct.

What is actually happening is that the meter is taking the rms value, which is the root mean square. calculation that basically gives an average, you know, a weighted average, I guess you could say of the voltage level, as it fluctuates up and down, positive, negative, back and forth, so 120 is actually a root mean square value, it's an average, so this is actually going up to I mean one 140 or so, if you do all the math, it will go up to higher positive and negative volts, but it all adds up and averages the rms value of 120 or 115 or 480 volts, okay, so that's really what rms tends to mean and that's really what these meters tend to tell you is the rms value that we all understand is the current value of the voltage that we want to know. .

Great questions here, let's see how much time I have to answer. I will try to be here as long as possible. I have maybe five or ten more minutes we can spend. Let's see if this meter has a standby button. It definitely has it. There's a hold button right in the middle below and what this does is. It can contain whatever reading you had last time, where it will basically say "Okay." It's fluctuating a lot, but this is where it was when you press the hold button, it will tell you a constant value that you can show to others or to yourself.

Can you take a look at it to understand if it is fluctuating a lot? Okay, so let's see that a cable meter is capable of measuring rms voltage compared to meters that are not capable of measuring rms voltage. Pretty much any meter you've ever seen is actually measuring. rms usually what we see is like at the fine level of these higher level oscilloscopes and those types of things where they can actually show you the waveform and what it looks like at that moment on that individual, could you? I know a fraction of a second level, um, that's what you know, looking at the actual voltage, um, power quality testing is really where it starts to get into well, what does the wave look like, is it a quality? higher or lower energy? that kind of thing, um, how much noise?

It's in the system that reaches the higher technology equipment, but generally a typical multimeter that we use in our work as electricians gives us the rms value, look, I like it, so we have an idea here, he says, when they are teaching the idea that thisindividual is teaching the idea of ​​open versus closed that same line voltage effect if you get a reading it means the circuit is wide open and if you get a zero then it means you have a good path and that's That's certainly true, where you could be By measuring a point of, say, a path from one part of the panel to another through a wire and if you get a zero voltage potential difference, guess what that means the path is good, the real problem arises.

If you get two volts, what if you get three volts? three volts, what does that mean about that path that's really where um, that's really where the ohms will tell us more of the full story this recording will be available yes, yes, yes, it will be. about two business days after this session ends, let's look at a big question, so I already hinted at this before, but let's talk about it a little bit, when you switch the red and black leads on a meter, you see a negative value in DC, while You flip them, um, you flip them on AC and you don't get a negative value, why is that?

And that's because the AC is already, uh, the alternating current is already fluctuating from positive to negative, positive to negative, so basically the current flows in one direction and stops. and then it flows in the other direction and it stops and it does it 60 times a second back and forth so the signal actually goes from plus to minus plus to minus plus to minus plus to minus 60 times per second very fast , and? what we're doing is just getting that rms value, which is a positive value no matter which way you slice it, 120 volts, as it goes up and down, that's what we'll tell you, so really negative is.

Nothing happens until you talk about DC, whose direct current is that the electrons flow in one direction and continue to the load, say the light bulb, and then flow back to the load. neutral back to the battery or other DC power source, so which just flows through the entire circuit one way, it doesn't go backwards, it doesn't actually go backwards, it goes forwards and that's why we use diodes correctly, if everyone is familiar with diodes where they allow current in one direction but not the other way around, it's like a check valve, but for electricity, um, that's really a way of converting AC to DC, so when you look at converters or rectifiers you'll see that they have diodes to turn the AC that wants to go back and forth just to let it go. forward quarter quarter quarter quarter and forward again can you discharge a capacitor with a multimeter?

Great question, so we strongly recommend that you use a properly rated capacitor discharge device to discharge a capacitor. and what's not an example of that is a screwdriver, or passing it to your coworker to prank him, that's not a good example of discharging a capacitor, some of these can pump out a brief burst of electrons, uh, at the point where they can hurt someone or kill someone so you have to be careful with that, can certain meters have the ability to have a rated capacitor discharge device inside them with absolute safety? That's possible, there are all kinds of different shapes and sizes of meters.

See why sometimes when I'm measuring 480 volts it gives me 500 until what measurement values ​​are good, is it okay to have 500 volts in a 480 volt system? It depends on the manufacturer of the equipment you are using. This general standard is that you never want to go about three to five percent of the total rated voltage above or below the rated voltage or what we call the rated voltage of 480. So if you think about it right, you know. 40 that's 20 volts right or so um yeah that's about 20 volts oscillating in either direction so you're right on that cusp where that voltage surge or swing could be caused by some problems in your circuit so yeah you're starting to regularly measure 500 that's getting to be dangerous territory as far as I'm concerned, but again, I can't be an expert on it until I actually see your facility, but definitely talk to our instructors about it if you're ever in the classroom.

In the coming months we will be able to talk in more detail about that. It's a big question whether fuses should be measured in ohms or AC. Great question, I say measure ohms, but the only way to do that is unfortunately you spend time doing lock and tag, uh. completely de-energizing the circuit, making sure with your meter that we have zero volts everywhere on all three phases, phase to phase and phase to ground, face to ground, face to ground, then we can take out the fuses and measure them on a table, that It's the best, surest way to tell if the fuse is good or bad, but if you don't have that capability right now again, you should do it like this, so if you're going to measure with live voltage, the key is that you never want to test again. top to bottom. bottom of the same fuse, okay, that's not really a good recommended way because if that fuse is bad on the blue fuse because it experienced, let's say, 10,000 amps of electricity that caused it to blow in a short circuit situation, guess what?

What does the fuse become? now if you go from the top to the bottom of that fuse holder, it's your meter and the meter could explode in your hands and doing these things has a big impact if they explode and they're not properly rated for the job, so, um, meters that Yes they are. properly classified for the correct category of work you are doing they should not explode catastrophically, they will definitely fail but they will not hurt you, they will not destroy you, or your hands, or your face, or whatever, if they are classified in the suitable category they can withstand the types of short circuit currents in the situations we are dealing with, so in terms of suitable categories for industrial electrical work, at tpc Training we say we never settle for less than category three, for so there are only four categories. three is for any type of industrial work, you know, three phase motors and control circuits, and category 4 is any time you go outside, you should be category 4 for these meters, is there a standard method for troubleshooting?

Did you know? That's a great question. It is not a safe way to solve problems. I'm sure that if you ask a technician one way how they would fix the problem, it will be different in slightly different ways than how another technician solves a problem, however, tpc us. know through all the research we have done in our different troubleshooting courses and coursework that we really have a framework on proper troubleshooting and feel free to let us know, call us after this you will see the phone number here and we can give you more. but basically it's an eight step process where you start by asking the right questions and using your senses just like we talked about today and then you can start using your measuring device from there and you have to be systematic about it and then from there , one thing I always recommend you do if you're troubleshooting is: no, what's the word, don't ignore or don't mistreat, I guess you could say the machine operator is right so the people who are actually operating the equipment day in and day out that you need to fix, they know if there's a lot of information and they try not to push the machine operator or the equipment operator out of the way and just try to fix the problem yourself. seen, they've heard, they've smelled, they've seen what's been going on and, um, you probably can, you can probably figure out what's wrong most of the time just by listening and asking the right questions of the equipment operators, okay, great. question, um, come on I see a lower voltage than expected, what does that mean?

So let's say I measured across the line to neutral and I know it's 100 volts or 105 volts, there's been a voltage drop somewhere right and a lot of times this can happen if um let's say our main panel that was giving us 120 volts was half a mile away, like on the other side of a warehouse, and then we ran the conduit non-stop from that panel to the other side of the building. just the length of that wire, let's say thousands of feet of copper wire, whatever size it is, has what we call a resistance that builds up along that wire, so that when you get to your panel and you measure the line and the neutral. on the panel, just like we did before, it may not give you 120, it will probably give you 110 105 depending on the length of the cable, so you have to be careful with the distance and if you need to increase the voltage again. through some type of transformer before reaching these panels, also low voltages could be all kinds of problems related to power quality and cleanliness.

I guess you could say how clean your power signal is if there are a lot of motors running or a huge motor is starting up in your facility, it can actually lower the voltage, uh, let's say, your lights, that's why Some of us, when we are in our homes, turn on the microwave or turn on a heater and the lights dim. a bit, that's a lower voltage for a period of time while something else is causing a large disturbance to the system. Unfortunately, I don't have time to answer everything, but I'll do my best to answer just one or two more, okay, and then we'll call it a day, let's see, great question, this is some great clarity here.

One safety issue that everyone needs to be aware of is making sure you press and hold, make sure the hold button is not on, that it's turned off. before checking the voltage because if you accidentally set the whole button to zero and you are measuring the voltage, it is on standby, it will still show zero and you could fool yourself into thinking the circuit is dead. Great point, oh this is a good question. We didn't quite get into the idea of ​​meg ohmmeters, right, meg, if anyone is familiar with those acronyms that we use, you know mega mega ohmmeter, how many ohms is a mega ohm, that is, 1 million ohms?

So, there are ohmmeters out there. that measure mega ohms now what is a megameter? What is the use of measuring a million ohms? This one, these megameters and this one can actually measure megohms if I measure it in the right place. It's really useful for measuring megaohms in devices where we wonder. whether the wiring that is in them, say a motor, a switch or a panel, is not making contact with the metal casing it is in or the motor casing it is in, then if it has, say , three-phase motors, motor coils within a motor. or a series of coils inside a motor and test that one wire of your mega ohmmeter will be in the coil of the motor and the other wire will be in the metal casing of that motor, say a screw terminal that is there There should be no connection between the live wires that are normally live and the case, and if we even correctly read 5 million ohms or 4 million ohms, guess what is low enough that we can start to see only slight current leakage from the live wires, so think? about it and write about it if you ever want more information.

There is an NFPA book. I'm sure we're familiar with NFPA 70, the national electrical code, and NFPA 70e, arc flash safety, which is the standard for electrical safety in the workplace, which, by the way, is coming out new this year, the third. It's nfpa 70b as in boy and fpa70b is the maintenance standard for electrical equipment and that gives us how many of those, how many mega ohms a, let's say, rotating piece of equipment has. equipment like a motor or a switch like stationary equipment should read if it is working correctly according to the standard and that is around five mega ohms last time I checked where if we are reading five mega ohms or less we should start taking some action to fix this before we say the installation on that wire breaks to the point where we're going to have a ground fault, okay let's see, cool, so some people talk about their categories here and that's cool, so if you're working on three phase and you have a category two, I say it's time to put that meter away, talk to your employer, your boss, your supervisor because category two is only rated for 120 and 240 volt branch circuits, like in a house or a hotel or something on the commercial side if it's three phase circuits, um with motors and that kind of stuff, category three is the way to go so definitely keep that in mind that's kind of the standard of the industry when it comes to the four categories of meters and again the name of that book I was referring to is nfpa 70b as in boy and to close us absolutely is that using a meter is risky, in fact, I need you to understand the seriousness of use a multimeter you can't just walk up in shorts and t-shirt and measure something with a meter, including unfortunately your own light sockets in your homes.

This meter touches when we are measuring voltage, it touches active electrical circuits and the only thing between all that current and voltage potential coming out to you is this little meterhere, so you really need to make sure you understand how it works, that you use it correctly within your specifications, and that you are very systematic about where you choose to test based on your understanding of the system as a qualified electrical worker. Thank you all so much for your curious questions and I really appreciate you being here. Thank you again for being here and everyone have a wonderful day.