Okay, this lab we're going to look at measuring resistance. And we've got the three values here 3.9 K, one k 22 k, here are the colors for each one right there. And again, this would be my first color, that would be the color closest to the end of the resistor as we shown previously. Let me clear the slide hearing here. And I've given you the upper limit the lower limit of each one. And you know from my previous discussions, when we measure the resistance, for instance, if I'm measuring this 3.9 K, a 3900 ohm resistor if my value on my reading That resistor falls between these two numbers 4095 and my lower limit 3705 ohms.

And the resistor is good. So we're going to look at each one of these. We're going to measure them. And you're going to see it's probably not very difficult to measure resistance with a multimeter, especially if I have an automatic rate raging on that. Alright, so let's stop and, and take a look at that now. Okay, here's my meter, and we're going to measure the 3.9 k ohm resistor.

And you can see here that I've got my black meter lead my red meter lead, and if you follow my red leader me, you'll see that my yellow clip lead is connected to one side of the resistor. All right. Now I'm going to take my meter and I'm going to go to the ohms scale or resistance scale, right there. All right. And you'll notice we see Oh l on the meter meter screen right there. Okay, that's because it's open.

So what I usually do is I usually shot my media leads together, which I'm going to do right now. And I'm going to try to stay out of the way. And if you'll notice, I'm reading. Well, let me get a good connection now. 00 ohms, which which should, should be because it's a, it's a shot. Okay.

So now what I'm going to do is I'm going to notice I've got the one one green lead connected. I'm going to take these, this other lead here, and I'm going to clip it here to the meter lead, and I should measure this value of that resistance. And we're reading 3.88 k ohms. If you can see it, you can see that the K is right here on the meter. All right, it says k ohms right there. Let me see if I can is a K and there's no.

All right. So and there's my decimal point right there. So 3.88 k ohms. Now the published value of this resistor is 3.9 K. Are we in spec? Well, if you look at that chart that I gave you that first bullet, Yeah, we are. Let me see if I can, I can bring it up here.

Let me change that. And if you notice, if we are between these two values, 495 or 3705? Okay, the resistor is good. And that's the first bullet. So we're reading 3.88 and we're good. We're good.

So that value that resistor is in spec. Okay, so let's let's look at the next one one kale. I'm going to start the video. I'm going to set it up, and we'll look at that one in a minute. Okay, right now we're going to look at a one K resistor is my color brown, black, red and the tolerance band is gold. Alright, it that means it's 5% resistor.

It's 1000 ohms. So 5% of 1000 ohms is 50 ohms. Okay, we have an upper limit of 1050 and a lower limit on that resistor of 950 ohms. So when I go to measure that resistor, If the value is between my upper limit which is 1050, and my lower limit, which is 950, ohms, then the resistor is good. So let's, let's take a look at that. Here.

I have my meter. Let's expand that now. Let's do it. There we go. Okay, I've turned it on. And what do we have?

We've got point 997. k, all right there, kale. Okay. And, ah, here's my resistor right here. All right, I don't know if you can see the color code there. But it's a brown, black red right there. And so ideally, this resistor via my meter is 997 ohms.

So is that meter good? Well, let's let's let's take a look here, and see All right. If my value is between thousand 50 ohms and 950 ohms, the resistor is good. We are reading $997. So that resistor is in tolerance. It's a good resistor.

All right. Okay, so now, let's, I'm going to turn the meter off. And there we go. Now the meter is off. So let's, let's stop here and do the next one. Okay, we're going to look at the third one here.

And we got 22 K, which actually is 22,000 ohms. All right, here's my color, red, red, orange goal, that would be the value of the resistor. And I'm going to find 5% of that. If I do my math, that's 1100 ohms. Right there. I do my math.

And I get 22,000 plus 1100, I get 23 100 ohms. If I subtract 1100, I get 2090 20,900 ohms. All right. So when I go to measure this resistor, if my value of the if my meter measures that value between 23 100 or 20,900, then my resistor is good. So let's take a look at this. Now.

I'm going to make this full screen. And let me let me turn the light on here is my resistor right there. All right, and there's my meter. I'm going to turn my meter on. I'm going to the scale And look at that, look at that. 22 k ohms.

On the.if. You can see it. Here's my K, my K. All right there is right there, if you can see that. So we are reading 22 k ohms. What's the published value of the resistor? 22 k L. Okay?

I mean, if you look at we measured voltage, we measured current and now we're measuring resistance. Resistance is pretty much if you if you get a meter, it's auto ranging, and it's going to give you the best scale. So I mean, the hard part probably is, depending on your eyesight, deciphering the colors on the resistor itself. I mean, that may be a little bit more difficult than actually putting the resistor across a multimeter and measuring the resistance and that Something that each individual is going to have to have to deal with and, and find out the the best way for them to do that. So with that said, that is pretty much it on measuring resistance. We're going to, we're going to measure a wrist not a rheostat.

We're going to measure a potential ometer in the next one real quick. And that will pretty much in this lab. So we're going to stop here and we're going to look at a potential ometer Okay. Okay, we're going to be talking about potential geometers here, and right here, Here I'm showing you on the top, top portion here we're showing you up. Dual gang potentiometers concentric tenshi ometer a multiband. Well, I'm sorry multi turn potentiometer.

And right here is the schematic representation. Have a potentially ometer. And here's how we spell it. All right, let me let me change my pointer here. And what I want to say here, before we go on, we've got to explain this right here. But let's talk about this, this and this and I want to go to the next slide here because I've blown that up.

And if you look, you will see two sets of terminals here. And actually, if you look, you'll see them right here also, there are two sets of terminals. And basically, what they do when they say gang is we have two sets independent sets here and the center arm. Or we could call it the wiper. He wrote they rotate at the same point. All right.

So let's go back to the other slide. And let's, let's go back on that I, what I what I'd like to do here before I go back, let me erase this, because we're probably going to need this the slide. Alright, so now let's let's get rid of the the markings on here also. Okay, so now, let's just see how this works here. All right. All right.

Here's my own meter. And again, we're going to do a lab at the very end of this. And we're going to actually physically show you how to how to measure the resistor and this this will become a lot clearer I'm sure. All right now with a pencil tenshi ometer All right, the endpoints here and here stay the same. It's a fixed resistor. So if I go across the potentiometer at point A and point B, all right, right there and right there.

It will stay the same. And this is what I'm saying here. Okay? The resistance from A to B equals 10 k. Now, in this example, and let's, let's, let's go back here. Let's go to the next slide here. If you'll notice on the previous slide, I can turn the shaft this way, so I can hold on just like a volume control.

All right. Well, a potential iometer is a volume control. So I can turn the shaft all the way. If I it's placed on a counterclockwise, I can take the shaft and turn it all the way clockwise. Let's go back. All right, the rotation from counterclockwise to clockwise on a standard potential ometer is 270 270 degrees right here.

All right. So now if I take the 10 k right here, if I take the 10 K and divide that by 270 degrees, we Get 37 ohms per degree. All right now what does that mean? Well, let's let's look at here. Okay, let's, let's erase the. Okay, so what's half of 270 degrees?

Well, that's 135. All right, and that's what I call the midpoint. Let me get my pointer. That's the center right here. And I call that the midpoint. All right.

So 135 times 37 ohms is a prop, approximately equal to 5000 ohms. If you'll notice original On our example, all right, the resistance from A to B is 10 K. So I found that the midpoint, all right, then the resistance from A to C is a, and his c would be 5000. And the resistance from B to C would be 5000. All right, so basically what I'm doing is I'm taking and just regard this for a minute, let's, I'm taking, just connecting that there and putting a meter lead right here. And I'm measuring the resistance from A to C, this way. That would be 5000.

And obviously if I break the connection here, And measure from BTC that would still be 5000 ohms. All right. So let's clear that. Now, if my if I rotate clockwise 67 degrees and that's approximately three quarters, okay? A to C. I'm sorry, that would be a quarter A to C would be 2500 ohms. And B to C would be 7500.

So as I as I move the rope, if I move that shaft, basically what happens is That shaft turns the wiper here. And that moves up and down. Alright, so the two endpoints, A and C, A and B affects, but I can change the resistance from A to A to C, or B to C. Okay? And the last example right here, rotation of 203, that now that's approximately three quarters clockwise, the resistance from A to C would be 7500. Okay, resistance from A to C would be 7500. And the resistance from B to C would be 25 on it, but look, look at this if you haven't realized it already.

Notice when I add up the resistance From ADC to BTC. In this example, it always has to equals 10,000 ohms or 10 k ohms. Alright, now I'm giving you a 10 an example of 10 k ohms in this in this slide, but potentially auditors come in multiple multiple multiple variable resistors. They come in one k two k 100 ohms 500 ohms 20 k 50 k. There's a variety of them, but they all work the same way. If I have 100 k on, all right, and it's a standard potential iometer then I would take 270 degrees and divide that into the value of the potential ometer. And that would give me the ohmic value per degree.

In this case, we're using 37 ohms per degree. All right, that is for a standard potential ometer. All right. So let's let's and I just want to add, let's clear the slide here. All right, now, let's go back to this slide here. And notice I got a multi term potential letter right there.

Well, this multi term potential yamana works the same way. As these guys here. The only difference is it were on a standard potentially ometer. It's 270 degrees for the center arm to go from here to hear. On a multi turn potentiometer it may be 10 terms, five turns. All right.

So to go from, if it was, let's say it was a 10 turn 10 turn, potentially ometer. All right. If it was a 10 turn, going from here, from this guy here, going from here to here, I would have to rotate the shaft 10 times fully. What does that do for me? It gives me a finer adjustment. It gives me a finer adjustment.

If you look over here if it was a conventional potentiometer Okay, and I could go from counterclockwise to clockwise and 270 degrees, then I get 37 ohms per degree. But what happens if I multiply that by 10. In this example, if I multiply that by 10, or divided by 10, or whatever, instead of being 37 ohms per degree, it would be 3.7 ohms. Actually, it'd be a lot less, because instead of going 270 degrees, we're going 360. So it would actually be less than 3.7 ohms. So I can get finer adjustments with a multi turn potentially on it.

Okay, and again, that may be used on a, if I'm doing a very precise calibration, or scientific applications where I have a circuit I've got to be very precise, then I may use a multi turn potentially on there. All right. Okay, let's let's move on here. Okay, we have a potential geometer right here, and I'm gonna walk, expand this webcam over here, right here in a minute. But what I've got is I've got a five k potentiometer. All right, let me let me expand my, my webcam.

Here we go. And if you'll notice, here's my potentiometer. Here's the physical potential ometer. And my meter is connected to the two endpoints. Now this is a five k potentially ometer. So let me turn on my meter.

And we should read approximately five k across that let's see what we get. Well, we get an overload that's that's not right. I'm not sure why not Let me let me check the connections of the meter here and see if we got a good connection. Probably not. Not, that's why I my descent fell off. So let me connect that.

Now let's see what we get. And we get 5.36 k now, these potentiometers are not resistors. Okay, so we're not going to get unless we get Yep, I mean, this is just your basic potentially ometer wasn't expensive. I bought it at the electronics store. I think it was like 89 cents. Alright, so it's not a high quality or high precision.

It doesn't have to be. It's for a volume control. So it said it's five K, we go between the two terminals here, and we're getting 5.39. That's fine. Right. So what I'm going to do now is I'm going to take one of these, and I'm going to go from the center to one end of the potentiometer.

Let's see what we read. And we're reading point 596 K, so we're reading about a half a K. And if I turn this and I'm going to go one way, we're getting 2.4 ohms. So let's go up the other way. And when I go all the way to the end, I should get close to 5.39. We're getting 5.37. All right, now if I take this end here, and go to the other leg here, it should be close to zero.

And it is it's 1.4. And if I turn it the other way, then we should go up to maximum value. You have this, which is 5.37 K. All right. So that's the point I'm trying to make. If you if you turn this here, the resistance will vary. And that's what we're doing now.

And I mean, that's how I potentially Amata works. So right now we're reading about 788 ohms. If I take this and go the other way, I should read, it should be the difference. Let's see what we get 4.63. So with both ends, like I've showed you on the previous lecture that I talked about potentiometers if I take this 4.63 and then go over here without doing anything, turning the knob, that that should add up to the whole value of the potential iometer file. Point three, seven.

So that's that's pretty much it here. So I just wanted to show you that it's not a big deal. Follow along, I showed you a five K or 5000 Oh, potentially ometer there's many, many different values, we've got five K, two K, one k 10, k 20, k 100 k. And, and they all work basically the same. Some of them have a larger rotation, where we have multi turn so I can get more precision adjustment. This one's just your basic volume control, I think the the range is 270 degrees. And that's that's pretty much it.

So with that said, This ends awesome lab one. I hope you enjoyed it. And we'll see you in awesome lab to where we get into AC voltage a little bit more there. All right, we'll see over there. This is alpha males electronic class. From saying, take care and happy learning