Oscilloscopes For Audio 101 - Part 3 - Oscilloscope Basics - How to Use One

[Music] hey welcome everyone mark here at bluegill electronics today we're bringing you part three in our oscilloscopes for audio 101 series we have gotten great feedback on parts one and two thus far so super excited today to get to bring you part three in this series hopefully for part four and five will come just around the corner here in the next few weeks and oh yeah by the way this today marks our 300th youtube video that we will be posting so take a minute and celebrate a little bit with us but let's dive on in all right here's the series we've got going if you haven't watched parts one and two i'd highly recommend you go back and do that some really good foundational stuff there part three we're going to cover today just the basics of an oscilloscope and how to use one okay just it's kind of like remember the first time you ever got behind the wheel of a car and all these gauges and dials and knobs and shifters and whatnot and it kind of it's intimidating right but now you get out you go out jump in your car back out the driveway you don't even think twice about it and you probably don't even look at half those gauges or dials an oscilloscope's no different it's got a lot of knob spells and whistles but you probably don't use two-thirds of them and the ones you do use you probably don't adjust all that much so we'll show you that today next week i'm wanting to just get on the bench with both a digital oscilloscope and an older analog scope and just do a bunch of testing get you guys head kind of where my head's at when and use the logical steps of an oscilloscope to try to solve problems inside of audio gear and then part five which is what i really wanted to make to begin with but but everybody talked me into making parts one through four first here i want to show you how to use an oscilloscope to analyze your audio quality and your audio signal so stay tuned for those let's dive on into part three today all right let's dissect the most basic definition here of an oscilloscope it says it's a type of electronic test instrument in other words a box that you can use to measure things with okay that graphically displays varying signal voltages in other words it's designed to look at ac waveforms okay you can measure dc with an oscilloscope but it's kind of boring and honestly a digital multimeter does just just as good if not a better job of doing that okay so we're going to be looking at these varying signal voltages usually as a calibrated two-dimensional plot don't let that scare you we're just basically looking on a screen at one or more signals as a function of time so in other words we've got this ac waveform in other words a varying voltage and it's varying over time right and you can see here this little green line that we've drawn right it's a sinusoidal waveform and it's going up back down back up and that thing does that repeatedly over a given time interval right and it says here then the displayed waveform can be analyzed for property such as amplitude okay what's the height of this voltage how much does it go up in voltage how much does it go down in voltage what is that amplitude okay frequency how often does this thing happen okay how often does it repeat does it happen once a second does it happen once every minute once every micro second things of that nature we can look at rise time the amount of time it takes to go from zero to its peak right time interval right what is the length of the waveform right distortion and other factors and you can see here on this little chart usually on the x-axis we mark time so how long does it take for this signal to do its thing and come back and start over again okay and on the y-axis here we're looking at the magnitude of it right so how big is this waveform all right when you have a varying waveform that repeats itself over and over and over and that's what we typically measure with an oscilloscope okay and this just happens to be a green sinusoidal waveform here that's repeating itself you can pick any two points in a signal that happens once in the waveform but then happens again when that waveform repeats itself and you can measure the distance between those two in seconds how long did it take from the time it happened once till the signal repeated itself and it happened again and you measure that in seconds that is known as the period of the waveform okay when we're talking about audio work typically the period is measured in milliseconds sometimes microseconds okay but what you don't find us engineers you know technicians and audio geeks we don't run around talking in terms of time and period you don't hear when someone say oh the frequency of my signal takes 12 microseconds to repeat itself right that's a lot to say it's just not what we do what we do is we talk in terms of frequency okay and frequency is a super simple math equation it is the number one divided by the period in seconds okay so let's do an example here let's say this signal repeats itself right in 16.666 milliseconds now a millisecond is a thousandth of a second so every 16.666 milliseconds this thing repeats itself let's do the math then 1 divided by 16.66 equals 60. we then talk about this in terms of its frequency as this is a 60 and the the met unit of measurement for frequency is hertz okay so we then say this is a 60 hertz signal which means it happens 60 times a second or once every 16.666 milliseconds okay if you can grasp that you're like nine tenths of the way through using an oscilloscope already and you may not even know it i thought we'd just do a quick little history lesson for a minute here back in the day we had analog based crt cathode ray tube based oscilloscopes they work great they're all you ever need for audio work to be honest but a little bit of downside to them in that the waveform displayed on this you're going to have to actually count these little gradients here and count your waveform yourself and you're gonna have to do some math yourself so if you want to figure out the frequency of your waveform you'd have to count left to right in terms of seconds right milliseconds and then you'd have to do the math yourself over here on a calculator and say 1 divided by what i came up with ah that's what the frequency is so nothing wrong with that it's doable but what happened next was oscilloscopes evolved a little bit and they evolved they were still analog crt based you know a little bit nicer cleaner screens um but what happened was they started adding digital measurements displayed on the screen as well so you can see these four waveforms being displayed here by the way this is the 2246 on the bench behind me here um you can start to see here the waveforms being displayed and you can see here this is 0.5 volts 0.5 volts 0.5 volts 0.5 volts and oh yeah by the way at 20 microseconds so it's giving you that frequency and time displayed on the screen screen right there okay beyond that what happened was a further evolution and these two kind of happened at the same time or similar time frames to be honest you got the digital display but a lot of oscilloscopes had these little modules built on top of them here that were considered digital storage so they also had some ram so you could take a snapshot of a waveform and save it for later and maybe compare that waveform to another waveform right so it was starting to let you capture things over time which is which can be handy for certain uses i don't use it that much when i'm doing audio work and then finally the modern digital lcd based oscilloscopes that would by the way do all of these things they do the on-screen display they can capture waveforms and play them back to you things of that nature okay so don't matter which of these you pick you can still do audio work some of them some of the ones over here on the right just make things a little simpler and keep you from having to calculate stuff on your own remember earlier i talked about this repeating frequency or repeating waveform so that can hold true regardless of the shape of the waveform okay so a sinusoidal waveform repeats itself and we can measure that a square wave repeats itself in terms of you know a series of pulses almost you know this little triangle wave form here this little bit of trapezoid waveform or over here on the right this is an audio signal okay but if you'll notice maybe there's a bead in the background to this audio signal right boom it happened here boom it happened here boom it happened here boom it happened here and so it it that beat behind the scenes maybe the repeating part of an audio uh waveform here and so that'll become important as we talk about how to trigger on a waveform here in a little bit all right finally on the bench but i want to orient you a little bit so as i dive into the oscilloscope um you understand what i've got going on so up top here i've got a function generator nothing special about it it has a couple features to it that a lot of function generators have one here it will let you change the type of waveform so we a little bit of a triangle wave there sine wave square wave and we can play with different things here okay we're going to leave it on the sine wave for most of the part but this may be one button that i vary and if i do i'll tell you i'm changing the shape of the of the waveform the next thing it will do this knob right here it allows me to adjust the frequency now remember earlier two axis here right the x-axis that we're going to talk about in terms of time or frequency and the y-axis we're going to talk about in terms of voltage amplitude okay so as we vary this you'll notice what's happening down here to this waveform it's changing right and it's changing on the time axis okay so that's a four kilohertz 4.3 kilohertz signal so in other words 4 300 times a second uh this waveform is repeating itself and i'm going to roll it down here to roughly a one kilohertz okay so 1000 times a second this signal is repeating itself and when i say repeat itself it's from this peak to this peak here to here is only half of a repeating signal it's got to completely come back to the same point now i could measure from the bottom to the bottom that's the same as measuring the top to the top you could also measure where it crosses the zero point here and the zero point here in the middle and that would help me understand how long that waveform takes to repeat and we could read that out in frequency happens to be happening a thousand times a second so i will be adjusting this little knob here and when i do i'll tell you i'll be adjusting the frequency we'll see it going this way next knob here that we need to concern ourselves with is the amplitude so watch what happens when i turn it okay the signal gets bigger in other words more volts peak to peak so the signal gets bigger less volts peak to peak the signal gets smaller okay so if i talk about varying the amplitude that's what i'll be doing and we see that increasing or decreasing here on the y-axis that's really all i'll be doing with this unit today so frequency shape and or amplitude let's get zoomed in on the oscilloscope itself one more quick thing all i'm doing is coming out of the main here the main output and it's just a bnc connector that i've plugged the nc cord into a piece of coax cable i'm coming down here i'm feeding into a little t connector here so that i can feed into channel one i'm coming out the other side of that t connector with just a single black cord here as you can see that does nothing but go from here to here that way i've got the same signal feeding in on both channels of this oscilloscope and as you can see if i wanted to measure what's happening in channel 1 and 2 i could do that so just a simple coax connection here that i've wired up all right textronix does a pretty good job here and apologize for the noise in the background both these units do have fans and there's nothing i can do to get rid of the fan noise but textronics and most oscilloscope makers do a good job of kind of grouping things together for you so this whole section right here is about the on-screen display and how your waveform might show up okay along with this little thing here called a power button push it in to turn it on push it in again to turn it off um right here grouped together we've got some functions around some on-screen displays we've got our vertical section of the oscilloscope we've got our horizontal section of the oscilloscope we've got over here our triggering functions and that's really all it is so as we break it down it's pretty simple and we're going to walk you through each and every one of these sections here today so let's start down here okay if you can't figure out how to operate the power button you probably shouldn't be watching my video series here and i'm just playing with you a little bit but here we have something called a intensity okay i want you to watch what happens when i turn this my trace goes away my beam okay or it gets super super bright till it's blinding me here in the room okay and i see people that run their oscilloscopes like this super bright i even see it in some youtube videos it's not such a great thing because what's happening is you're hitting the beam on the back of this phosphorous screen really hard and over time you're going to wear out the phosphorus on this more likely than if you run it down here something like this so what i do is i run mine just bright enough that i can see everything clearly but not bright enough that it's starting to blur or blind me there so and i'll tell you i've been using this oscilloscope here for probably a good 15 years or more um and not any problems burning up the phosphorus here there's also a knob here called b intensity and it's for a a time delayed signal you can do a zoom in function and look at little pieces of this signal i'm not going to be showing that as part of this uh audio or oscilloscope for audios series but that that would let you adjust the intensity on that zoom in function okay up next here we've got the focus button notice what happens when i turn it to the right trace gets really blurry notice what happens when i turn it to the left trace gets even blurrier here it's just the screen focus remember remember on tv's years ago you start to turn the little focus button so you just turn it kind of the null between both both sides of blurry until it's the absolute sharpest and you leave it alone okay up next we have something here titled readout now this oscilloscope happens to have a readout that shows you what the settings are for for the horizontal and the vertical so what this is telling me that each of these little gradients right here this is 0.2 volts okay per little box okay so if i looked at this signal i would say one two boxes going this direction one two boxes coming down so that signal total would be point two times four or point eight volts peak to peak here now i can do that math myself on an older oscilloscope that doesn't have these little little displays down here to tell me you actually have to come over here and read it on the dial itself so you just read on the dial and it would say 0.2 volts per division right but this one this one just happens to display it on the screen same here with the milliseconds it shows the time base so if i change the time base i'm changing that if i change the volts per division i'm changing the readout on it i never varied the signal i'm just i'm zooming in and zooming out on that signal via more or less volts per division and more or less time on the other axis okay so what this readout knob is is it is the intensity of that little readout if you notice i got it super bright or i can make it completely go away there there again i just put it bright enough that i can read it and no more and leave it like that okay and last here you've got something called scale illumination okay this little oscilloscope i leave mine down all the time i don't use it but you can turn it up to the point that illuminates the little lines on the scale here and you can actually see those and you can see here it's outlined and it's kind of arranged behind the screen at this point in time yeah it's just something i i can see my my you know if you're working at night and couldn't see the the scale or something with the dark in the room maybe you want to eliminate it but okay the next little section we're going to talk about today is the vertical section and when it talks about vertical guess what that means this axis over here right on the y-axis okay so right now i've got it set on channel one this is there's a little section of buttons here and i've just got it on channel one which means i'm only reading on channel one of this oscilloscope by the way this is a four channel oscilloscope i keep these that i don't use often kind of covered up and and you'll notice there's dust on top of that what that tells you is i do a lot of audio work and i only use two channels so if you're thinking you need a four channel oscilloscope to do audio work probably not it's a hint good two channel scope will do everything you need okay um so with that got this little knob here that i turn and guess what i vary the volts per division now notice i have not changed my signal at all i did not change the function generator so my signal has not gotten smaller just the volts per division now i'm at 0.5 volts per division so each of these little blocks here it's 0.5 volts i can take it on down to one volt per block okay remember remember earlier i said this was a what 0.8 volt peak to peak signal so if i move this up until it's sitting on the middle line it would take me up to just below the next little line there and i would be seeing that i have a 0.8 volt signal there okay now you notice something i showed you i showed you the position this is arbitrary you can put it wherever you want right if you put it dead in the middle then you could kind of know that is the center line of your signal here and by the way it's kind of hard to work with a signal like that right i like to get my signal on up there so i'm using a lot of the screen here you don't want to get it too far though that you're starting to go off screen top and bottom so something like that right there might be a good place to be at okay so i'm varying my measurement here not the signal the same exact signal in both of these scenarios okay now if you'll notice here i've got channel one i've also got a channel two button i'm gonna push the channel two button so what i've got going on now is i have channel one and channel two both going on on this screen and this little set of knobs right here controls channel two so i can have channel two on a different voltage base okay 0.5 volts per little section right versus the 0.2 volts okay it just flattens my signal out i also have a position knob here that i can use to move the channel 2 up and down so i got position for channel 1 position for channel 2 here and then there's a button here in the middle that lets you add these two signals together and it shows you a third waveform that is the sum of those two waveforms added together there are times you might need to use that maybe not so much for audio work okay so let's just take it back to a single waveform so this little piece here in the middle little knob it says v-a-r on it it's variable so if you'll notice here i've got 0.2 volts here i've got 0.1 volts here i've got 0.5 volts what if i wanted 0.3 volts per division right well that's what this little variable does it lets you vary somewhere between the other two settings and what does it tell you is greater than 0.5 but it doesn't give you the exact readout i'll tell you i use that function almost never in doing audio work i can almost always measure what i'm wanting to measure somewhere on screen just by varying the divisions that it gives me okay let's take a look here so we've covered these buttons and by the way if you turn channel two on and channel turn channel one off now i'm seeing what i'm feeding into channel two it's the exact same signal i'm feeding in here as i'm feeding in right here right let's do this let's put it on channel three interesting what do we have we have a flat line okay that is zero volts in other words we just have a signal going in there is no varying amplitude because it's right here there's nothing plugged into it at all right but one thing to notice about channels three four and two they all share the same time base okay so if i turn channel two on and i've got three channels going if i turn channel four on i've got four channels going um and by the way you can uh you can use different position knobs here to put put the different channels where you want them like you could put one down here maybe you put one up here you can just put them on the screen where you want them to be able to look and see at different things but what i was just showing you here let's just say we only show channel three here that's what a dc signal looks like so if you're looking at zero volts dc it looks like that if i was to to crank up the voltage and have uh 0.5 volts let's say i had one volt signal all i would have is a line straight across two bars up from that it's pretty boring to be honest and that's why you don't use an oscilloscope a lot to measure a dc signal okay so you kind of get this controls channel one this controls channel two and you're like well channel three and four over here if you'll notice they share um controls with this and so one time base for all and then channels three and four start to share the voltage um base with channels one and two so that's why they're i don't use them that often they're not that super effective if that makes sense all right so we've shown you here with two channels we can vary positions of each of those i've shown you we can turn signals on and off i'm showing you we can add between them okay coupling here we go hang on one second all right here we go coupling what that is is when you feed your signal into your oscilloscope right here okay and it's an ac waveform feeding in but sometimes your ac waveform is riding on top of dc in other words it's not biased around zero volts maybe it's a 5 volt dc signal with a 1 volt peak-to-peak signal writing on top of it which would mean it's going from 5 volts up to 6 volts back down to 5 volts down to 4 volts and back up okay you can see that here but if i happen to put this unit on dc and i let's just say i applied some dc voltage to my signal did you notice what happened my signal rose up by the amount of dc that i applied to this signal okay well that's good and grand you can see hey my signal is riding on top of some dc component and it's it's moved up because of that well what if your dc signal that it's riding on top of happens to be 200 volts you just lost your signal and you're not going to find it it's going to be way up there okay so you can switch this unit over to what's called ac coupling and all it does is put a coupling capacitor in line with this signal and it removes the dc component watch this let me put it back on this watch i'm going to move it up here okay so it's starting to go offline because i've got this dc component added to my ac signal watch what happens when i ac couple it brings it right back down and then i use the position if i want to hover it around around the zero mark there okay you're just removing the dc component of the signal feeding into this oscilloscope okay by the way i almost always leave this unit uh on ac coupling on both of these for audio work just for whatever that's worth okay there's a little uh while we're over this way there's a little box here called calibrator and what that is is you can use it to calibrate your scope probes okay if you'll notice your scope probes have a little calibration thing right here what you do is you plug your oscilloscope in let's put it on channel two and take it off channel one then you just clip your probe onto this little little signal here and if you'll notice then um it'll tell you that it is a one kilohertz signal at .5 volts okay and if you'll notice here i've got this little swoop up on my signal i could use a little bitty screwdriver to adjust the scope probe right here it's just a little trimmer capacitor inside of there and you would get that signal as flat as it could be and what you're really doing is calibrating your scope because it's putting out a known signal right there that's what it's used for okay while we're over on this side there's also a little button here called beam find and i'm going to show you how to use that a couple things in one more button i need to show you i've been showing you can do the position of your signal this way up or down there's also a button here that does position and by the way this works for all four channels you can kind of slide your signal off to the left or off to the right so let's say you want to count from the beginning of this little signal right here you might move it all the way the peak you might move it all the way to the left there until it touched the very edge of your screen and then you could say one two three four five or almost five um and you could count that way so that's the reason for the vertical position well let's do something here i put it back on dc coupling let's let a let's add a little bit of uh let's just say you clicked on with your oscilloscope probe and boom you don't see anything on your screen anymore but yet you know there's a signal there okay you can use this beam fine button and look what it shows you see that the bar the line at the top it's telling you that that signal is going off the screen upwards right so i can then grab my position button and start scrolling it back down and then you can kind of see it come back into focus here and you'll see it's back online here okay now what if it was out the bottom okay well let me uh let me take it down this way with some dc offset negative okay there we go this line down here is brighter than that line it's showing you it's off the bottom you would know to turn your signal upwards to get it to where you want to need it okay let's say it's off the screen to the right too far you can see here it'll give you an indicator that it scrolled off to the right or to give you an indicator it's scrolled off to the left so it's just a way of finding your beam if it happens to you know you happen to hook up to something boom like whoa where's it at i don't know how to find it do i adjust this to adjust that what what do you do um beam finder will tell you exactly how that thing's up top i need to bring it back down and find a home for it here all right check this out we've already learned this whole section these two we've learned the whole vertical section here let's get over here into the horizontal section okay horizontal is just it's just that it's the x-axis and we're starting to play with time right so if you'll notice one millisecond per little division okay and i can shift this using the position button kind of get it right there on the peak of one and you'll notice one millisecond between these divisions and because i'm on a one kilohertz signal here you know to go from the bottom up all the way back down right or if you started in the middle up down back to the same point either way it's one millisecond in between those i can flat you know i can make it really really tight between these i can stretch it way out and kind of zoom in on this thing you know that's a practical level right there for measuring an audio signal okay you've got something here called 10x magnification if you want you can zoom in on that thing gives you a 10x going this way now 10x going horizontally you typically pick that up via a little switch on your probe here to go from 1x to 10x but if you want to go 10x this axis it actually gives you a button here on the oscilloscope to give you a 10x function back and forth okay up next you've got say you've got two signals going on channel one and channel two here okay there's a little mode selector here that you can go so on the time division you can go a and go b you can kind of alternate between them or you can go x y and i'm not going to show you that today really most 90 of the time you're gonna leave it on a in video five we will use the xy mode and i'll talk about that but both these buttons here do nothing more than move up and down in between those um this little light here will come on to indicate that you're on variable and that you're so like what happens if you accidentally hit that little button and you didn't notice it right so you're over here playing with things you're like god things don't seem right this little light just tells you that you're on variable in other words you're not locked in on a calibration the same here if you'd happen to bump that and get it off this little light comes on here to tell you that you're not locked into a specific voltage there per division okay and remember earlier i told you that um that you could do this little time delay thing i had mentioned well that's that's uh that's here where you're starting to zoom in on part of the signal and uh see parts of it or whatnot but there again not going to get into that in this video segment and that trace separation is tied into when you're doing some of those types of some of those types of functions so in reality then all you have left on the horizontal side here is the position of channel 3 the position of channel 4. the volts per division kind of markers here that they have for each of those channels that's really it as far as it goes is vertical and horizontal this right here we'll talk more about it here in a little bit and then position as we talked about earlier was kind of left right on your signal so up next let's talk about triggering so what is this triggering thing we speak of okay you notice we got a nice clean sine wave right here okay and a sine wave is really easy to do what we call trigger on not all signals though or sine waves and not all signals are nice and clean like this so some are more difficult to trigger on and this whole section up here in green is dedicating to triggering and you say what the heck is triggering well let me give you an example okay this is an untriggered signal okay in other words it's not locked onto that sine wave okay the oscilloscope's time base has to get in sync with the signals sign base otherwise your signal is constantly scrolling one direction or another and not locked in and so it doesn't show your repeating wine sine wave over and over and over well when you have something like this a repeating sine wave and yes my drawing is horrific you typically pick a spot on this sine wave and let's just say it's this spot right here on the upswing so the slope going this direction okay and you want to lock in on it so you would lock in it there you would lock in on it again here because you're on the upswing you'd lock in on it again here the upswing and it uses these little upswing measurements to say hey based on that this is a repeating signal and we are going to we're going to hold that signal steady on the screen that's what triggering is now if you'll notice this little button here it says when it's lit up it's triggering on the upswing okay i could change this over to sugar on the downswing so in other words i would be triggering when the signal is going downwards and i could pick a place here on the downward slope where i'm going to trigger each and every time and it would hold this signal true to that okay i could trigger on the peaks up here i could put her on the very bottom of these signals and let me show you why you might not want to do that so what if your signal repeated every so certain per certain time base but the amplitude was different every time it repeated say the amplitude was higher every other time well if i triggered on the upswing way up here guess what i'm going to be triggering on a signal that is this time base and not this time base what i may end up with then is much like i showed earlier something that is scrolling like this and not locked on to every single sine wave that's taking place okay now what happens if i've got a signal that this big signal here happens let's just say once every uh 10 microseconds or milliseconds whatever but these little things here the little ripple or modulation that's taking place on the peaks happens at a much faster frequency so maybe this is one kilohertz and this is happening at five kilohertz or five megahertz something else if i triggered on the upswing right here i would also pick up this and this and this and this and my time base wouldn't be based upon what i'm wanting it to be based upon and watch this signal instead it would be based upon here here here here and what would i end up with yet again i would end up with some kind of signal doing something like that so you're wanting to pick the wave form that you're wanting to trigger on and what that does you've got a knob here that's called level okay and with the level you're basically adjusting where on the up swing if that's what you've if you've got it illuminated there you're adjusting see notice how i got it swinging off um so that trigger determines the level of where you sleep then there's this thing here called hold off and that that determines the time from when you pick a spot until it tries to find that spot again on the scope and let me give you an example here so here this one i can use the holdout to try to get it to lock on but it's all i never can totally get it to lock on you may wonder well why can't you ever get it to lock on here mark well this little whole section right here is based on what do you want to trigger on well if i put it up here i'm basically i'm triggering on vertical on channel one in other words whatever this setting is on is what i'm triggering to if it's on one volt here i'm triggering based upon whatever settings are on this style if i go down to just channel one then i have to pick the level of what i'm what i'm triggering on along this way if i go to channel two right the other channel remember i'm feeding the same signal into it so it happens to trigger the same but i'm triggering on channel three well guess what there's no input into channel three so i have no idea what it's triggering on right now and you can never lock in because of that the same with channel four here okay but if i get it back on channel one if when you have a sine wave most of these scopes like right now i've got it on auto level it'll find a level and it'll lock on it this auto sent auto sensing piece it's pretty darn smart and it'll lock on just about every time here's the good news about all these little buttons and knobs over here so this this here auto then you can go down to auto auto level auto what is that runs after this is normal normal ties back to what's on this then you've got lines so 60 hertz it's locking on that you've got something here called tv field and then you can go external which is on the back of the scope here another bnc input that you could sync to a time base of okay so you kind of got what do you want to sync to or how do you want to sync then you've got what do you want to sync to over here and then this is just another you can say hey let me let me look only at the ac signal this would say let me look at the ac signal plus the dc this would cut out any noise let's just put some filters in line this would cut out some high frequency noise that may be getting in your way some low frequency noise and whatnot so um anyway i typically leave mine on noise over here i typically leave this triggered on channel one and i typically leave this up here triggered totally on auto the good news is i don't have to touch this 90 of the time when i'm dealing with an audio sine wave now if i'm actually looking at a real audio wave which is made up of a lot of frequencies all at one point in time i may need to play with these trigger things the good news is these are the only two knobs you really just have to adjust one and or the other until you get locked on trigger wise you can't go wrong here you can try everything over here right so if let's say your signal's scrolling you can't get it to uh to lock on and you know you're playing over here with different time bases and different levels and you can't ever get this thing to lock on there's nothing you can do here that will harm the oscilloscope just play around until you get it to lock on so you don't have to be a scientific expert at this you can be a little bit of an experimenter and just play around until you get your signal locked on good news is most of our audio testing we're going to be playing around with sine waves or we'll be playing around with square waves and with both of those it's really easy to lock onto either this up scope or down scope or one of the peaks here and if you put it in auto it'll pretty much find it for you and make life really simple okay so triggering 101 not a lot to it after all um if we were dealing with much more complex waveforms let's say we were dealing with a tv signal so you've got an audio sub carrier built in there that's at you know somewhere between maybe 10 hertz up to 20 kilohertz and then you've got that you know being modulated onto you know some high frequency um you know up in the hundreds of megahertz range and you're trying to take a look at that it can get pretty complex or if you're trying to look at digital signals but for for remember this is this is oscilloscopes for audio 101. um triggering is a pretty simple thing for us okay so we have pretty much covered the vertical now the horizontal okay how to trigger keep in mind these two little things here are just tied to the position of channel 3 and channel 4 up and down you do have a little volts per division you can either set it here on what would be 0.5 volts or 0.1 volts on channel 3 or 4. and if you need to use channel 3 or 4 just read your manual on what those mean i'm not i'm not going to get into it but it's fairly simple really all that's left is this little section here that kind of comes up and goes down along the screens here and this is measurements okay so what you can do here is you can turn this unit here you can put it on volt so it's actually got a digital multimeter built into it kind of and i always use peak to peak here so i'll push this button these buttons here correspond to what's on the screen so when i push that if you'll notice now i've got a line going across at the top and the bottom and it's measuring the peak-to-peak waveform of this and it's telling me here in a readout on the top i've got 1.16 volts from peak to peak and it'll tell you here what's it reading channel 1 peak to peak okay if you'll notice as i vary the amplitude what happens those lines redraw now i'm measuring the 0.64 volt signal here on the input right it'll it'll it takes just a second but it'll change with you okay up next here you can do a time measurement okay if you'll remember time would be how long does it take this signal to maybe go from this point right here to this point right here so i could push this button here for seconds and it'll this is where these two knobs right here come into play the one on the left will adjust over here and you get it in the middle of your peak right here and the one on the right will measure the distance between and then you kind of get it on the next peak over here and what is it telling you right here 270.4 microseconds in between these two lines what i say earlier us self-proclaimed engineers texts uh audio geeks we don't talk in terms of time we like to talk in terms of frequency so push this time button again then it'll do one over seconds which is what did we say earlier it's frequency what is it telling me we have a 3.698 kilohertz signal from that point to that point and if i looked up here at the top i've got three point six eight three on my meter up here and you say well why is one three point six nine eight one three point six eight three here's the reality i probably don't have this thing exactly on the frequency and if i get it exactly on on both sides all right now i've got 3.68 kilohertz and up top i've got 3.68 kilohertz we're spot on at that point so you know a little bit of uh variation there is you uh you know very very touchy controls and uh but you get you get in the ballpark you got the reality is you got a 3.68 kilohertz signal there okay this little button here um just kind of uh clears the screen of that all these buttons are tied to what pops up on top and i'm not going to get into these other buttons because you don't use them that often but hey the manual will tell you what they do if you want to if you want to dive deeper but for our purposes um you have kind of seen what this oscilloscope needs to do guess what we've just walked through all the crazy buttons and knobs on this oscilloscope and showed you everything that they do let's do this let's unplug this unit and we're going to finish off our glass of wine here along with it and we're going to get out a digital oscilloscope and show you the difference one of the major differences you're going to see right out of the bat oops this little whole section right here that's kind of tied to how a cathode ray tube works will not be there for a digital oscilloscope so it makes it even easier you don't have to worry about all this stuff okay here we are this is my rigel 1054 ds 1054. i paid about 300 bucks for this probably four years ago great little oscilloscope there there's newer models out now there's also the hand tech there's other really nice oscilloscopes in this 300 to 350 range and for audio work this will do all you ever need and then some look it's very similar to what we had before we've got here right our channel one we've got a position knob here look at this when we change this we're changing the amplitude but instead of being displayed over here on a knob it is being displayed down here on this right here right 200 millivolts per division 500 millivolts per division but guess what look at this this vpp right here it's measuring it automatically and it it's measuring that the peak-to-peak tells me exactly how many millivolts constantly so much faster than what i was doing in there before okay you can also turn it on channel two here see the other signal turn channel one off right there again vpp on this 100 millivolts right here um i can also see what i see here the period the frequency i'm on 712 or 714 hertz right now my vpp for 184 millivolts here at this point in time or whatnot it's just the same okay i can change the time base here and tighten this up changes the time brace and i can open it up the difference is all these things that were a lot of buttons on the other unit look at this ac coupling what you do here push the button tied to that it's all menu driven then you push this button in now i'm dc coupled okay so if i have some dc offset on this unit look at that it varies the signal right as i change the dc offset i come over here and put this on ac coupling right here click on it whoops clicked on ground by accident ac couple it right now i am varying my dc offset but what does it do it always settles back down and it cuts out that ac component i can limit the bandwidth of this unit if i want i can tell it i'm using a 1x probe do you remember the other day hang on we had plugged this unit in our differential probe right and look times 50 times 100. watch this i can come over here and say my probe my probe happens to be on 50x i can click on that right and it'll change everything based upon that take it back to 1x okay so super smart little units lets you do honestly a lot of things that the unit i was showing you earlier can't do i can invert my signal i can limit the voltages over here on this side i can measure period i can measure frequency i can measure rise time i can measure fault i measure how long it takes the signal go from here to here how long it takes to go from here i can measure the width of each signal lots of measurement capabilities over here on the left just by clicking on this like right here i can click frequency on channel one here all of a sudden right here i'm measuring this is a 712. look at this as i change the frequency instantly this thing is measuring the frequency over here on the left and displaying that for me over here on the right you've got trigger look at this remember before i would adjust the trigger and i didn't see a line here it lets me see a line exactly what i'm triggering on so if i had something that alternated every other time and it was smaller the second time around i could make sure i'm far enough down and it'll tell you the voltage level the level that it's actually triggering on here over here on the left i can click on menu and i can say hey i want to measure voltage max or voltage this or voltage peak to peak okay as soon as i click on voltage peak to peak there right there now i'm measuring my voltage peak to peak and as i vary that voltage watch it it'll read instantly what's going on over here so these are just really smart units but keep in mind everything's kind of menu driven versus knob driven so i actually think the learning curve is a little longer because you have to learn the various menu functions and some of these are two or three or four steps deep in the menu but once you learn it remember i said this in my first video what is the best oscilloscope you can own the one that you learn so if you get an oscilloscope say you buy this rigel and you learn everything about it it is the best oscilloscope for you i don't care what anybody tells you learn the oscilloscope you have learn every function of it learn how to work it for you and and it'll be your best friend this one has a lot of stuff up here it'll let you acquire signals and capture that picture and maybe measure it over the next 10 seconds and then play it back to you there's just a lot of functionality in these but at the end of the day you can also use it very simplistically just put it on channel one just vary the voltage right volts per division change the time base right use the position here it's not rocket science and it's very similar and by the way you can see my little trigger level right there that little little things showing me on the side right there what my trigger level is at all times super simple nothing crazy one thing i do like about these little digital scopes got a usb port on it if you'll remember on this unit to get it to work what did you have to do you had to plug in a usb power cord this provides you the usb power cord right on the front of it ready to go so if you're going to be using a differential probe one of these is a nice way to go now okay just a few more things before i wrap this up if you'll notice here there's two ground lugs over here two separate ones one is tied here on the unit to basically you could tie ground here and tie it back to something in your audio unit and it would tie the internal ground sync on this to the audio unit the other one here is actual chassis ground and we'll we'll talk about that a little bit more in video four when we actually get on the bench hook this unit up hook it up to you know a piece of audio gear with a dummy load and measure across the dummy load things of that nature so stay tuned on that and i failed to mention on the previous oscilloscope it had a banana jack that you could have plugged in and tied the ground of the oscilloscope and down to the ground of whatever you wanted inside the audio unit and if you use some kind of device to isolate the the ground then you could have kind of floated that ground and tied it to the oscilloscope next though um if you'll notice here notice how this signal is a little bit jagged along the way it's not perfectly smooth here okay that has to do with the resolution of the lcd screen now you may say well gosh that's kind of rough and it looks super smooth on your other cathode ray but cathode ray tube based oscilloscope mark well the reality is the cathode ray tube it just takes longer for the fluorescence to fade out so it always looks nice and smooth so there's a there's a smoothing factor that happens on a crt based oscilloscope just from the fluorescence and how long it takes to go away and this may be actually a little more accurate however there is the resolution of the lcd here that you actually have to deal with so so you may say well when do i use one of these versus the other i actually like to use my 2246 on the bench a lot i love it it's simple to use i love all the knobs i don't have these deep menus i'm always hunting for and and whatnot so back to it's the oscilloscope that i know well so i use it all the time however anytime i'm not on my bench i don't want to pick that big old 2246 up and carry it somewhere if i'm working in here in the workshop area or i'm going to a friend's house to test something out or whatnot this is what i'd carry with me and i and i love this unit nothing wrong with it it's just not my day-to-day scope i actually like the cathode ray tube base but it's just what i grew up on and what i learned so it's what i'm familiar with and it's kind of like you know what's your favorite car well it might be the one you know how to drive the best you know um type thing or favorite bike or motorcycle or whatnot anyway hope you guys learned something i had a lot of fun making this video part four we're going to get on the bench and actually use these things to actually test some stuff and get you thinking how do i use my oscilloscope to solve audio problems okay or how do i determine if i even have a problem with my audio on my unit via an oscilloscope and then video 5 we're going to get into audio measurements via an oscilloscope and tell how good your audio signal is using nothing more than an oscilloscope thanks again for watching everybody hope you're enjoying this series um if you've got questions ask them down below i'll do my best to answer them and uh let's let's all look forward to video four here in another week or so thanks everybody

Channel: Blueglow Electronics

Views: 17,401

Rating: 4.9906869 out of 5

Keywords: dynaco, heathkit, AR, audio research, cary, klipsch, marantz, luxman, knight, mcintosh, altec, sencore, tektronix, fluke, fisher, hh scott, western electric, akai, pioneer, sansui, harmon kardon, gibson, fender, mesa, 300b, single ended, tube amplifier, tube amp, solid state amplifier, krell, analog discovery, bottlehead, output transformers, transformers, hammond, alinco, atlas, collins, drake, dentron, elecraft, flexradio, hallicrafters, galaxy, gonset, icom, yeasu, hy-gain, kenwood, national, swan, ten-tec, passlabs

Id: 7T8hxhpHua4

Length: 56min 7sec (3367 seconds)

Published: Sat Feb 06 2021