EEVblog #926 - Introduction To The Oscilloscope

Hi, let's check out this cool device, the humble oscilloscope, the most essential tool in all of electronics. What is it? Why do you need one? And how does it work? Let's go. But before we take a look at the oscilloscope, both the modern digital type and the old school analog type, we have to take a look at the multi-meter. You're familiar with the multi-meter and how it measures voltage among things. Hence, the name multi: measures multiple things. Now we can put it on DC volts here and we can measure our battery, which is a DC source. There it is: 9.23 volts. No Worries. Right, but what happens if this voltage changes? hmm Now just imagine that you start to graph this voltage that you measure on your multi-meter. On the Y-axis here we've got voltage and on the X-axis here we've got time. So let's take this one sample here, at let's say at the one second mark. We measure that on the multi-meter and we get our 1.5 volts or whatever it is now. What happens if we keep actually taking a reading on our multi-meter every second or one-tenth of a second or one-fifth of a second or whatever the multi-meter updates at? You might end up with something that looks like this. And you might have noticed it looks something like this sine wave we get in on our oscilloscope here. And that's all an oscilloscope does: is it measures voltage on the y-axis here versus time. And if we hook our multi-meter up to our adjustable lab power supply here we can adjust that voltage and we can see that voltage change with time. It's not just one fixed value. But if I turn this not really quick, the multi-meter really has a hard time keeping up with that. And that's a huge limitation of the multi-meter: is that it does not allow us to view these changing voltages or signals as we call them. And why is that a big deal? Well, because practically all modern electronics works on high-speed signals that you cannot display on a multi-meter just can't see it changing with time so our oscilloscope is a window of voltage versus time here and we can slow it down with what's called the time base and we can display these signals now DC is not interested it's just a fixed line because at its at a fixed voltage but if we adjust that power supply whoa look at that it's jumping all over the place but that's relatively slow good thing about the oscilloscope is it allows you to view really fast changing waveforms so if we use what's called the horizontal time base here it goes from anywhere from seconds two milliseconds to $OPERAND microseconds around to nanoseconds like this and it'll just allows the slower the time-base the slower the . moves across there so the way we measure things on an oscilloscope is by this green here or what's called a graticule and you'll notice that it's volts per division 1 division is one of these little squares either horizontally or vertically that's why what's called the vertical amplify here is in volts per division so if we're actually currently right here on one it's one volt per division so each time that line goes up by one division bingo that's one volt and likewise over here on a horizontal time-base it's in seconds per divisional not . five seconds per division and there you go count it each time it goes across it takes half a second to get to H division this case it's not . one second so it takes one second to sweep ten divisions across the screen there and you'll notice that the dot goes across the screen or sweeps across the screen as it's called and then it retraces back to the start that's because we don't have an infinitely long screen but we want to be able to view waveform so it goes across and then jumps all the way back and starts displaying again and again and again on the same screen so if we disconnect that in feeding no voltage at all and look where that line is ok it's the second division from there we can actually adjust that to any position that we like and i want to explain why it's just handy to be able to work do this at the moment that's all you need to know then ok that is our reference point that is their ground . or zero volts . now if we plug in our signal it's gone up 12 divisions and we're at one vote per division so it's one volts 2 volts and what do you know we're feeding him two volts so we're going to circuit that we're analyzing then we can just take our source code probably chalks up we connect this onto the ground . of the circuit and then we can start probing around and having a look at some of the signals that are in our circuit now we never would have been able to see these with just a multimeter it's a window into another world so this signal that we just saw here look it's got a ground and then it jumps up where it at 1 volt per division here so 123 for like four and a half volts so we've got ourselves a digital signal that we're looking at we can change your time based like this not . 10 microseconds per division on a horizontal scale over here so we can see the time difference between these two points about one two three four five divisions there or not . five microseconds between these little pulses and we can zoom in using horizontal time-base you might have noticed that this just looks like one thing but we zoom into it huh look there's more even higher speed signals buried within their magic and the oscilloscope is the only tool that allows you to view this voltage versus time and to actually see all of the signals that are actually going on within your circuit is the essential tool for electronics are design troubleshooting and just understanding what's going on in your circuit you can't do without the oscilloscope and really that is all you need to know and the source code measures voltage versus time simple that's it really now feeding the same signal into an analog and digital oscilloscope here and the digital oscilloscope works exactly the same voltage versus time it's got a lot more measurement functionality and things like that but there's one crucial difference between the digital and the analog oscilloscope the digital one allows you to store the waveform and analyze it so it allows you to freeze it and then work on the signal later in debug it and analyzer but also allows you to capture single-shot events IE events that only happened once whereas an analog oscilloscope might be able to capture that so if you have a look at a very slow one heard signal on analog oscilloscope you can see that you can just maybe see a trial going behind it there that's because of the phosphor on the screen that's actually lighting up but this is not a storage oscilloscope so all you get is the current present value as it sweeps across but if you view the exact same one who'd seen on digital oscilloscope look the waveform stays there you might be able to sit on there it goes I'm so it stays on the screen at all times and of course you can press the stop button to phrase it at any time and if i have an event that only happens once for a brief period we can't see it but a digital oscilloscope we can put it in what's called single shot mode by pressing the single button here and it'll sit here armed waiting for that event to happen as long as you set up the trigger right and that's for another video until our event happens and bingo there's our event and we can zoom in and actually see exactly what happened there in this particular case I found some very interesting behavior here of when I actually switch on my signal intar function generator here using the output so it's got a relay based out with their and it's just doing something rather unusual i didn't know that bingo couldn't see that with an analog oscilloscope and if we hook our still scope back up to our power supply and put it in what's called a troll mode here then and I just the past fly you'll be able to see I am wiggling that and you can actually see it moving in real time because it acts like a yard chart recorder those old-fashioned are you know seismographs and things that you've seen it's basically you can see how it's changing with time and I'm twiddling the part on my power supply and it's following that so that's kind of like different to what we saw on the analog oscilloscope so that's just another way of representing now voltage versus time but the window just slides across it just keeps sliding going in that direction instead of that capturing but that is the subject of another video I'm sure so if i disconnect that our signals going we can't do anything with it but this weekend with the digital skype we can just press stop and bingo we can go in there and we can analyze that signal even though I always stopped it and we've disconnected that from the import we can go in there zoom in and out and play around with it and analyze that signal to our hearts content so that is an incredibly valuable insight and the reason why you should have a digital oscilloscope over an analog one and the modern digital oscilloscope allows us to measure all sorts of things automatically like the voltage from the peak the negative to the positive peak here and allows us to i get the average value the frequency and a whole bunch of other measurement stuff the rise and full-time which you may not be familiar with but all these insides into your waveform a modern digital scope can actually measure and you can turn on cursors for example and then you can go in there and it can automatically measure the exact time for you between that cursor and that cursor of the waveform so you don't have to go in there and count them manually and then squint and hold your tongue at the right angle and go I think it's near enough to that a modern digital scope can measure everything precisely now of course you have a multimeter isn't completely useless it can of course measure AC alternating current this is where the waveform it goes positive and negative voltages like that so if we disconnected but if we connect it up will notice that we've got a 1 kilohertz sine wave here and of course this can measure it can measure the true rms value of that changes signal and it's accurate up to a certain frequency read the data sheet for your multimeter 1.74 volts there we go rms voltage because the digital oscilloscope can actually measure and calculate this mathematically 1.79 volts there's a little bit error there but it's basically measuring the exact same thing so yeah this can do it but that's about all the motivation can do if you want to actually see your waveform you've gotta have an oscilloscope and seeing is believing because this is just a number this actually tells you what's really going on so there you go i hope you learned something about sooo escape here and yes they're complicated looking things but they so cool they give you an insight into what's happening in your circuit and if you're getting into electronics you want to figure it out you want to play around with stuff it is the essential tool and you can buy them for a couple hundred bucks so don't be afraid of the oscilloscope they look complicated but really it's just measuring voltage versus time all the extra stuff is just a bonus and they're really not that hard to use when you get into it and if you do anything you are a beginner and you do get into trouble and things like that you're marking around and you're doing all sorts of things and you're not sure what's going on and everything's not quite working for you and it's where's my way form you can actually just hit the auto button and it will hopefully show you at least get your basic waveform on the screen there it is right there and then you can start playing around with it although i do of course recommend that you learn how exactly how the source code works and get to know it intimately so that you can use it incredibly valuable tool the tool for electronics troubleshooting and I've got other our videos here which i will link in and at the end of this as well including one where i show you how not to blow up your oscilloscope with your ground clip lead here very important you understand ground in when it comes to a source codes and things like that so I'll link that in down below hope you enjoyed it catch you next time

Channel: EEVblog

Views: 332,414

Keywords: eevblog, video, oscilloscope, what is an oscilloscope, oscilloscope tutorial, how to use, timebase, vertical, channel, digital, analog, storage, how it works, introduction, basics, learning, tutorial, rigol, ds1054z

Id: Iq4QlfH-oqk

Length: 13min 7sec (787 seconds)

Published: Sat Sep 24 2016