How to Use an Oscilloscope - Mega Guide

science oh that's gonna still work right to find out we'll need an oscilloscope hi i'm daniel bogdanoff and welcome to keysight labs where we think testing should be the easy part most people get good at using oscilloscopes the hard way through trial and error years of trial and error ask me how i know this video is the easy way to learn oscilloscopes it will teach you more than just how to use an oscilloscope it'll teach you how to be good at using an oscilloscope that means we'll get technical in some spots but your alternative it's well years of trial and error there's also a giveaway at the end of this video as part of the keysight university live from the lab event sign up details are in the description one of life's greatest disappointments is that we can't see electricity usually so we have no idea what's happening in the circuit and even if we could see it things happen so fast we would never be able to follow it so along comes the oscilloscope an oscilloscope visually shows you what's happening electrically at the tip of your probe with respect to ground it's kind of like a camera but for electricity once you can see your signal you can make measurements debug your device's behavior and characterize your device's performance oscilloscopes come in all shapes and sizes well they're usually rectangular but this little guy is a couple few hundred bucks and this big chungus can punch in at over a million dollars what we're about to cover applies to both i'm actually going to use this one because the nice big screen works best for a video when you start using an oscilloscope the very first thing you should do is press the default setup button this will get rid of any weird settings left over from the last user who didn't watch this video and just started pressing buttons hoping it would work ah why won't this oscilloscope work i should have watched that whole video in its entirety and subscribe to the keysight labs youtube channel and given the video like it left a comment below then connect your oscilloscope to your device with a probe most oscilloscopes or scopes come with a set of passive probes like this they're not just a wire there's actual circuitry inside that helps make the signals pretty this clip goes to earth ground to give your scope a measurement reference it's important to remember that this is an earth ground connection and should only be connected to ground nothing else i'll link to a probing playlist in the description if you want to deep dive into probes we have so many pro videos once everything is connected you'll hopefully see something on the screen but odds are it's not going to be quite what you want to see like this so you can change it the easiest way to change it is with the auto scale button when you press auto scale the scope looks at what's coming into the scope and does its best to put something usable on the screen sometimes it works perfectly other times so it's important to know how to manually tweak the display to get what you want on screen oscilloscopes have four main controls that help you change what you see the first two control horizontal scaling and horizontal position the horizontal axis represents time and we can change the scale and the offset using these knobs i also have a touch screen so i can just do this notice that the screen has divisions on it to give us an idea of our signal parameters for example from here to here is about three divisions one two three and i'm at 90 nanoseconds of division so i know that my period is about 270 nanoseconds the other two main controls handle vertical scaling and vertical offset per channel most oscilloscopes have more than one input or channel and you can independently set each channel's voltage or current per division you can play with the vertical and horizontal settings until you're happy with what you can see so this knob controls channel one scaling and this knob controls channel once offset and again i have a touch screen so i can just move it up and down if i want oscilloscopes have more than one channel so you can see multiple signals at once and see how they behave in relation to one another for example you might want to see the input and the output of a power supply speaking of channels one expensive mistake people make is they accidentally fry the input of their oscilloscope by putting in too much power there's a maximum input setting printed on the channel but that's just for the highest voltage per division setting so when first setting up your signals you should make it a habit to start at the highest voltage per division setting and then zoom in until your signal fits on the screen this is a bigger concern on super high bandwidth oscilloscopes like that uxr because they can't have the same input protection as one of these and those are a lot more expensive but it's a good habit to form and it's a nice way to treat the electronics in this pepper astute viewers know that we skipped a step and didn't calibrate our probes it's important so here goes the first time you connect a probe to a scope channel you need to impedance match the probe and the scope and it's easier than it sounds connect the probe to the cal ports and get the signal on screen we want to see a nice square shape here this is a little off so i'll use the provided adjuster and tweak this until the edge looks sharp meaning our scope and our probe are impedance matched and this transmission line is happy fancy probes don't do this they're way too fancy instead they get a full s-parameter characterization from the factory the scope reads the s-parameter information from the probe and compensates it automatically it's super cool that our probe is compensated we can connect to our device i'm going to use a signal built into this scope sometimes all you need is a quick glance at the screen and you can tell what the problem is or see that everything's working fine often though you'll want to make some measurements you can do that the old-fashioned way by measuring the screen but it's not very accurate and can take a while to make multiple measurements for this let's see how long it takes to manually measure frequency period peak to peak voltage and rms voltage i'm going to get my tape measure i had to do some math i had to measure things and it took this long it's that long i don't know i can't see it instead of that you can hit the measurement button and add the measurements you need it's faster it's easier it's more accurate and you can save a screenshot with the measurement values right on the screen let's see how my manual measurements line up with the scope's measurements for my period and frequency i actually looked at the wrong label so i got it totally off the frequency according to our scope is 500 kilohertz for period i assume there was a 50 duty cycle so i doubled what i measured the pulse with it's clearly not a 50 duty cycle so according to our scope it is a two microsecond duty cycle i actually measured 320 nanoseconds hopefully i did better on the voltage measurements peak-to-peak voltage is added automatically when you turn on measurements i measured 2.05 volts the scope measures 2.14 that's pretty good i'll take it clearly though it's much faster and easier on the scope you could also do a quick measure and get a snapshot of every standard measurement i like to take a quick screenshot of this for documentation and as a baseline to refer back to if there are specific measurements you want to characterize maybe the maximum voltage over a million cycles you can turn on statistics and see how your signal performs you can see the cursor here showing that i'm measuring maximum voltage and all the statistics along the bottom you can see from the count here that the scope is actually capturing a lot of signals really fast and making measurements on all those signals also if you don't know how a specific measurement is made on this scope you can long press the measurement and the scope will tell you what it does actually any button or knob on this scope behaves that way a quick tip for making better oscilloscope measurements it's a common track to stack up waveforms on the screen if you want to make more accurate vertical measurements like peak-to-peak voltage you should scale the signal to be the full height of the screen it's a little harder to see but this optimizes the analog to digital converter in the scope and will give you a higher accuracy on your measurement for horizontal measurements you should scale the signal to fill the screen with what you're trying to measure for example if i wanted to measure the rise time for the setup and hold measurement it's best to put the edge all the way across the screen like this if it's frequency put a cycle on the screen now this has all been for a simple repetitive signal much like life it's not always going to be that easy so there are a few tricks you can use to capture weird or one-off signals one critical concept that's super important is it's critical it's also implied that it's super important oscilloscope triggers if you can fully wield the power of oscilloscope triggering you will be ahead of eighty percent of other scope users out there big brain time it works like this your signal is feeding into the scope in this scope it's just sitting here waiting for the right moment before it captures the data and plots it onto the screen it's not capturing randomly it's waiting for your signal to do something specific it has to meet the trigger criteria the signal is actually a lot of captures overlapped on top of each other it's nicely centered and pretty clean because we are triggering on a rising edge at zero volts autoscale did this for us it's also the default setting but what if we switch to a square wave that goes from 0 volt to 1 volt that triggering is on the zero level so let's see what happens this is not as pretty the scope is triggering somewhat randomly on the bottom of the square wave yuck fortunately we can fix it with flex tape or this knob this knob is easier to use and more effective but less waterproof this knob controls the trigger threshold and notice how my new trigger point is now at a different voltage now we have a pretty signal on the screen because we're consistently triggering at the same point in the cycle although there's obviously some other things going on with this signal you can also change the type of trigger to be something other than a rising edge so we can figure out what's going on here like this here we're triggering on a runt pulse but there are a ton of different options simple ones like pulse width and rise time parameters and complex ones like serial data packet errors or nth edge burst triggers this scope has a fancy one called zone trigger where you can skip complex trigger setups and just draw a box around what you want to see and now we can see both front pulses so choose the trigger that's best for what you want to see there are some advanced trigger settings you can play with too a scope is in auto trigger mode by default see it says auto basically the scope is gonna sit here and wait as the signals come in and it's gonna wait for a valid trigger condition and if it doesn't see when it says fine just capture and display that information anyways this is nice because you as the user can see what you need to tweak to get a stable signal but if you have a signal with an infrequent trigger it's super annoying because it just grabs signals and throws them on screen so you should switch to normal triggering mode which will trigger only when a valid trigger condition occurs boom this helps you avoid junk captures that you don't need right now there's a super rare pulse on the screen and i'm in auto mode so it's just capturing i'm going to switch into normal mode so it only captures single pulses and now when i trigger the single shot it captures it and it leaves it on the screen each time there's a new valid trigger condition it re-plots and captures the signal it's usually best to start in auto mode scale your signals to how you want them to look get your triggers figured out and then switch over to normal mode if you really want to geek out you can play with some of the other trigger settings the secret sauce to how this works is when the signal comes into the scope it actually gets split up into two paths one to the adc and the display and the other just the trigger circuitry this means we can do crazy things with the trigger path and not mess up the signal that we want to keep pure so you can ac couple the trigger path with a 10 hertz high pass filter reject frequencies with a 50 kilohertz high pass filter reject high frequencies with a 50 kilohertz low pass filter or even add some hysteresis on the trigger timing to prevent it from triggering on noise one last trigger capability you'll want to log in your noggin is trigger hold off trigger hold off sets the amount of time the scope waits after a trigger before re-arming the trigger circuitry this is nice for things like packets or bursts where you only want to trigger on the first edge and not a random edge in a burst you can increase the hold off so that the trigger only re-arms between bursts if i have a signal like this i squared c bus you can see it's not triggering well i usually just twiddle the setting until it stabilizes and there it's stabilized and if we zoom out you can see it's re-arming between packets you can also do the math on this if you want you just calculate how long a packet is and set the holdout to be somewhere between packets if all of that sounds too complicated you can just use the external trigger input on the back of the scope and let something else trigger your scope you are now an oscilloscope triggering master i mentioned you should use normal mode for infrequent trigger events but what if your trigger event is the most infrequent what if it only happens once maybe it's the boot up sequence of a chip or a super rare signal glitch that crashes your device you don't want to lose that signal once you've captured it so to stop your capture there are two different buttons you can press depending on your situation the run stop button and the single button use the stop button if the waveform you want to capture is on the screen the stop button stops everything once it's stopped you can make measurements save off waveform data add annotations and even save a screenshot using the save button then you can hit the run button again to start capturing the other button to consider especially if you don't have your signal right on screen is the single button the single button clears the last capture trace and does a deep capture on the next valid trigger right now the scope is waiting for that single shot trigger single is best when you know you can reliably capture an event happening in the future for example if you want to check the inrest current of a power supply as it turns on you would set up your trigger hit single to arm your trigger and then power up your power supply when you're ready to do it again you can hit single for another single shot capture or put the scope into parkour mode i mean free running mode now we know how to get the signal we want on screen how to make measurements and a lot about triggering sometimes though this still won't be enough to get the signal you want on the screen so here are some other ways to modify your signals to get better measurements or more insight into your device bear with me for a bit of theory by default oscilloscopes show you all your signal frequencies from dc up to the bandwidth of the scope and then it rolls off it's like a big pretty flat low-pass filter bandwidth is an oscilloscope's key banner specification and basically the higher the bandwidth the higher the price of the scope maybe you don't want all that bandwidth maybe you're looking at a power rail and you don't need 50 bazillion hertz of bandwidth on each channel you can turn on a 20 megahertz low pass filter to get rid of the extra high frequency junk noise is proportional to frequency so removing the higher frequencies is nice for measuring things like power where that noise is just going to get in the way of your actual data you can also filter out the low frequencies by switching to ac coupling this adds a 10 hertz high pass filter allowing you to filter out dc components and look at higher frequency components riding on a dc offset for example here we have some ripple on top of a dc offset it's really hard to zoom in and analyze that ripple this is passable i had to zoom in a lot and as soon as you scale off screen you're violating the scope's dynamic range which is not great that's probably a topic for another video but all i have to do is turn on ac coupling mode and that unwanted offset goes away and now we have a nice view of our ripple we can trigger on it we can zoom in on it make great measurements on it without violating dynamic range or having to do weird scaling things on my scope a common trap is to think of this as a brick wall filter but ac coupling is not you should only use ac coupling mode for sine waves above 100 hertz and square waves above 200 hertz or you'll have some weirdness another trick you can use when you want to flex on your lab mates is switch to a different acquisition mode right now the oscilloscope's analog to digital converter is grabbing sample data points from the signal at a rapid pace where my hands it's like 5 billion samples per second and then it plays a mathner's version of connect the dots to get this into a continuous line it interpolates the data you can actually change the interpolation techniques and we call these acquisition modes i won't dive too deep here but the default is the creatively named normal mode use it 99 of the time but if your signals have infrequent very narrow pulses use peak detect mode which is designed to grab and emphasize those outlier points if you want to reduce the random noise in your measurements use high resolution mode which uses boxcar averaging to do a rolling average of neighboring points you get a much cleaner view of your signal with this mode finally there's averaging mode which does waveform to waveform averaging only use this mode if you're certain you have a periodic consistent signal and you want to see an average of it over multiple captures this is nice for cleaning up super noisy signals and picking out waveform oddities that show up repeatedly waveform oddities would be a great band name once you've done all this and acquired the perfect gold and magic signal that would make mama proud it's still just a line on the screen you have to interpret it and that can be work so i prefer to make the scope do the work for me for example we've talked a lot about power if you want to measure power you need to measure current and voltage and then multiply them it's a pain to do this in excel so instead you can turn on a math channel and do the multiplication right on the scope you can set math channels to do a bunch of different operations play with it on your scope and see what's available on yours probably the most used math function is the fast fourier transformer fft this lets you see the frequency components of your signal this is that square wave with the sine wave rolling on top of it like we were looking at earlier for ac coupling and we can see the square wave fundamental and all of its harmonics as well as this little spike here which tells me that's the frequency of the sine wave that's writing on top of the square wave if there are specific technologies you need to dig into there are also dedicated capabilities and apps built into the scopes one that many engineers can't live without is protocol decoding for example here's an i squared c bus and we can see this packet is actually missing and acknowledged there are also some specialty apps that make testing much much easier on higher end scopes there are apps dedicated to things like pcie compliance and jitter analysis power's come up a lot today there are also a couple apps just for testing switch mode power supplies they automatically set up the signals and give you specific measurements for that type of test for example switching loss of a switch mode power supply i'm not going to go deeper into these because they get sort of specific but there's some great information out there for niche measurements including over 200 videos on this channel alone and of course oscilloscopes are now coming with all sorts of bonus capabilities like built-in waveform generators bode plotting tools frequency counters digital volt meters even real-time spectrum analysis check your scope's manuals for more information on those the user's guide for this scope alone is 526 pages and walks through every feature capability and mode on this puppy in glorious detail and no i didn't actually print the whole thing just the first page i'm actually about 50 pages short so congratulations you now know a lot about oscilloscopes but the journey doesn't stop here there's always more to learn i've had my hands on these things for years and i'm still picking up new information i'd love to hear your favorite scope tips and what scope you're using down in the comments you can also win a really nice scope and keep on learning with us over at keysight university live which is happening right now some of today's test gear winners are these wonderful folks the rest are over on the keysight university live webpage you can sign up for the event now using this link or the link below i'll see you over there

Channel: Keysight Labs

Views: 143,649

Keywords: oscilloscope, oscilloscopes, waveform, voltage, current, tutorial, keysight, electrical engineering, computer engineering, electronics, digital storage oscilloscope, mixed signal oscilloscope, best oscilloscope, oscilloscope tutorial, basic electronics, oscilloscope tutorial for beginners, oscilloscope tutorial pdf, oscilloscope tutorial for dummies, tektronix oscilloscope tutorial, oscilloscope tutorial part 1 - basic usage

Id: t_UTV_9dpTc

Length: 18min 52sec (1132 seconds)

Published: Wed Mar 17 2021