EEVblog #594 - How To Measure Power Supply Ripple & Noise

hi welcome to fundamentals Friday today we're going to take a look at ripple and noise measurement and specifications you familiar with it you've seen it on your power supply your bench power supply that you've got lying around no doubt you see that ripple and noise measurement they might give a typical value for a PSU like 1 millivolt rms / 5 millivolts peak to peak ripple and noise what exactly does that mean what's ripple and what's noise and how do you measure it what are the traps for young players well I'm glad you asked so what does it ripple mean let's take a look at that first and you're almost certainly familiar with this term you've seen it used in terms of linear power supply for example and we'll get into that now it can be correctly described as the charge discharge cycle of the storage element in whatever power supply you're actually using be linear or switch mode there's a bit of confusion there people think ripple only is 50 60 Hertz mains hum that sort of stuff out of your traditional linear supply that you're used to here halfway halfway of bridge rectifier for example and you capacitor then well you get that 50 Hertz / 60 Hertz depends on where you are ripple on the output of full wave bridge rectifier you'll get double that frequency and you've seen that it's a basic building block thing you've no doubt mucked around it with your scope if you're a beginner but that ripple the term ripple also applies to a switch mode power supply a DC to DC converter let's say for example this our buck converter here which you know converts a higher voltage down to a lower voltage the storage element in this case is the inductor here and the charge discharge cycle of the inductor in the switch mode converter and that will give you you know it doesn't look quite as smooth usually as your mains frequency which are is derived from the mains which is of course a sine wave you don't generally get a sine wave it you might get something sort of funny-looking like that but it's still going to be periodic and relatively low frequency in of a switched-mode power supply could be you know tens of kilohertz up to a couple hundred kilo it's maybe even a megahertz or two or something like that but it's generally defined as that base frequency of the discharge and charging of your storage element be it your rectifier here or your inductor your DC to DC converter so that's sort of base frequency and well what is noise easy noises everything else pretty much mainly due to in terms of a switch mode power supply for example you generally won't get noise in just a linear power supply like this unless it's being coupled in via something else but in a DC to DC converter for example you can get parasitic inductances all over the place and they can cause some high frequency noise or ringing when you've got large di DT technical term it just means large changes in current over time which you get charging and discharging your storage element these parasitic inductances generally much lower inductive values so therefore they're going to ring and generate noise at a higher frequency so you'll find that the noise typically will have sort of you know noise superimposed on there like that I can't draw it in there but you'll see that'll have much more higher frequency content and that's generally what noise is and in terms of power supply specifications well they lump them all together and say it ripple and noise so they combine the two and they give you two figures they give you a peak to peak value of course which is your value from there to there your absolute maximum peak the absolute minimum and they also give you a value in rms as well at least you're good suppliers do and I power supplies they might just give you the RMS value big as well marketing blank right the RMS value is always going to be lower than the peak to peak value now I've done videos on noise before and you should probably know from those that a noise figure is generally pretty useless unless you specify it over a particular bandwidth and what is it in the case of our supplies well a lot of manufacturers will not tell you so there's actually no real standard for it as such pretty much manufacturers will just throw a number out there 1 milli volt RMS they won't even give you the bandwidth what does it mean in fact they won't even tell you what current it is at because the riddler and noise is going to change with your output current the noise for example the parasitics in the adductors the value of the change in current with time that i talked about there well that's going to vary with your output current so the voltage and noise figures well unless the manufacturer actually specifies it you've actually got no clue it's it's kind of almost meaningless but there is a semi de facto standard for it and that's 20 megahertz bandwidth so generally if it's not mentioned that's what the manufacturer is really pretty much telling you that it should be over a 20 megahertz bandwidth both ripple and noise hence why your oscilloscope has that bandwidth button on it and it's 20 megahertz or vice versa the bandwidth figure was taken from the fact that scopes actually had 20 megahertz bandwidth limiting on and yet analog scopes for a long time had sort of like a base level 20 megahertz bandwidth so really a the number was just sort of picked out of the air pretty much but most scopes should have that 20 megahertz bandwidth limit on it and if they don't well if you're using the wide bandwidth your scope you're going to get the wrong result you're not measuring it properly so if your scope doesn't have that how you might have to build up an external filter to put inside and that's all there is to the theory pretty much in fact I've probably spoken longer than I should let's go to the bench so let's take a look at two typical power supplies here we've got this power tech MP 39 it's actually a Manson 9400 I've done the teardown of this before it's just rebranded and it's just a high current switch mode power supply not really a bench power supply as such and then you've got your higher-quality rygel DPA 3 2 up here let's take a look at their data sheets so here's the Manson 9400 and well look it's basic ripple and noise 10 million volts RMS as I said they are just too scared to put in the peak-to-peak figure in there and they don't even specify a bandwidth or anything like that and of course they don't specify what output current it's over but almost no manufacturer actually specifies what output current it's actually at all different values for different output currents so it's generally taken the ripple and noise figure generally taken to mean at the maximum output current or maximum output power point and here's the wry Goldy p83 - and look at this much better here we go rip LED nose and they specify the bear with 20 Hertz to 20 megahertz as their de facto industry standard they're a 20 megahertz but hey it may not always be so there you go normal voltage mode here it is once again they've lumped them together and we've got less than 350 micro volts RMS / 2 milli volts peak-to-peak so that's a pretty low noise power supply so which one actually means more to you the RMS value or the peak to peak value well actually that's up to you and your requirements for the circuit you're actually powering but generally speaking the peak to peak value is really you know that's the one that's going to be a pain in the ass because you will get those peaky spikes out of it as we'll see on the scope so you might think it's pretty easy to measure the ripple and noise of your power supply just hook your oscilloscope probe up to the output like that and and measure it with or without a load on there but hey that's rule number one is that generally the rippln noise is going to be higher at higher load so you generally want to test it at either the maximum output current or your intended output current for your circuit under test for example so we've got a 5 volt output here and I've got it connected up to my BK precision a constant current load up here and I've set it for two amps so there it is it's drawing two amps let's go over the scope and see how we set it up and because power supply measurements are typically going to be low amplitude values like in the terms of millivolts or even sub millivolt really you want the best scope you can get with the lowest noise frontend with if possible you know a good 1 milli volt per division range or in this case the Rye goal mm series scope has a 500 micro volt per division range fantastic ideal for testing power supply stuff like this or pretty much as we'll get into anyway the way you want to set it up is well here's channel 1 feeding our signaling you always want a C coupling you've got to remove that DC content of course bandwidth limit very important because we have to measure over the bandwidth we can disable well we can go into say 100 megahertz or turn it off and look at that that is the difference between having your full bandwidth or your what the actual specification is over a 20 megahertz bandwidth so if your scope doesn't have that height you'll have to add a series filter in there and I've set up normal mode manual triggering on this so I can adjust the trigger level and well look I can get it to not trigger at all barely oh yeah we got a big spike there but barely because I'm adjusting the trigger level like that it can't be tricky to actually trigger on noise like this so generally you want your trigger threshold maybe on a noise peak like that for example so anyway generally you don't want to use your auto trigger mode sometimes it's not going to work very good anyway what we've got is our RMS value the scope can tell us the RMS value before scopes could calculate this sort of thing you would typically use a wide bandwidth multimeter specifically for the task with a true RMS value mode to give you the RMS value but these days your oscilloscopes can do it and we've got look at current value of not sure if you can read that but it's like 2.6 million volts or something like that and these are the statistics average and then the peak to peak so there's our two figures we've got 20 you know almost up to 20 millivolts peak to peak there and of course we can freeze that and actually take a look at the waveform what we're typically getting that's pretty ugly pretty noisy but hey I've got some basic figures there but you might notice something here I've used a times fixed times 10 probe for this thing well that's not so great when you're doing noise low-level measurements like this you don't want to using that divider probe really so you want to stick in at times one probe so I've changed that to a times one probe and there it is I've set up as times one we basically get in similar values to what we got before similar waveform but you're going to get a better signal fidelity out of your x one probe because you're not dividing it down but another trap is that with a x one probe as you've seen in previous video I've done is that the times what the bandwidth of a x one probe can actually be pretty low in the order of like 10 or 20 megahertz so just check the datasheet for your particular if you're going to use a scope probe like this check your particular probe and what bandwidth because you may not be measuring over a 20 megahertz bandwidth anymore you may actually be limited by the bandwidth of you scope probe there you go I'll link in the video for that down below if you haven't seen it we've got an older scope with limited memory depth during regular sampling then you might need to use peak detect mode in fact you probably should you know as a general rule be using peat detect mode so that it can actually detect the absolute peaks and you're not missing it based on your time base and your memory depth and stuff like that so if you want your true peak to peak reading it should be in peak detect mode that's what it's there for and just to show you how that ripple and noise changes with load well that's with my 2 amp load if I turn off my 2 amp load bingo look at that big difference so yet make sure you know and specify what low current you're testing of that but you guessed it I've deliberately added a trap for young players here the probing method that I've just showing you before is actually wrong you shouldn't be doing it like this and I'll show you why it won't be a huge example I could probably set up a better example but you'll at least see the difference at the moment I've got my LED studio lights above me and their pulse width modulated and those things generate you know a whole bunch of noise which gets coupled into our test system here in our test leads and everything else absolutely horrible stuff so what happens if I turn off my lights here watch the waveform you won't see a huge change but you'd see a difference already there we go and if I switch them back on there we go you actually get a bit more noise and it can actually be a lot worse than that depending on the scenario and how it's actually being picked up in fact I'll show you a much better example of let let's hook it up to my Rygel 8:32 power slide exactly the same as before five volts out we're drawing two amps into our load over here and I've got my standard oscilloscope probe times one with our earth lead on there let's check this one out and as you can see totally different waveform totally dominated by you know high frequency noise content because this is a linear power supply as opposed to a switching power supply that we saw before and we're down to one milli volt per division here let's that's with my lights on let's turn off ready tada look at that huge difference let's switch it back on well look at all that that is common mode noise being picked up by our piss-poor test connection we didn't do it right so the next rule of power supply ripple and noise testing don't use your big antenna lead like that it's a huge inductor just picking up all sorts of crap so instead what I'm going to get is a BNC adapter like that and I've got a banana plug to BNC like that and I'm just going to plug that into our power supply much better so we don't I mean I can still leave this lead dangling off here it's not doing anything anymore but generally you take that out and then we can plug it straight in nice low impedance low inductance path through to our power supply connection right at the test connection by the way you always want to measure it right on the output and not way over here you don't want to measure it over here because well that is just going to pick up all sorts of crap forget it so there we have it beautiful low inductance path directly in our load connected directly across they're probing via the BNC fully shielded no big inductive path that's as good as we can possibly for measuring the output of a bench power supply like this and what does that give us look at that and that's with my lights on look I'll switch them off and tada look it adds very little high frequency noise to that where is it 1 millivolt per division we can actually go down to 500 micro volts per division because this scope is really really good and look we really can't see those lights up switch mine yeah there we go we've added a little bit more but it's nothing like before it's like you know half an order of magnitude less and more what we're getting before because we've got a proper low inductance shielded test connection but now the problem is with that what's called single end and connection that we're testing with at the moment that that's good and you can do power supply testing like this but it's not absolutely ideal because we still don't know where our noise sources are coming from look we've got some spikes here I could probably try and not trigger off those but you can see it drifting across like that are they being generated insulin by the supply or is it coming from something external something you know and we're getting common mode coupling onto our cable well I don't know and for those curious to see what it looks like on a real old-fashioned analog scope which is still the best choice for something like this well here's my Tektronix triple - 5 once again it's also very rare on the market that's got a 500 micro volts per division vertical range and see you know we can see a bit more detail in the high frequency content in there but we could also probably see that on our digital if we actually stopped and zoomed in and stuff like that but there you go we see we're also seeing some of that noise which are not sure if that's still common mode noise common mode pick up from something or what but there you go generally basically exactly the same thing we'll seen before on our analog scope and there you go I've got that a bit better on the digital scope over here I've triggered manually now so I'm in there and I've got AC coupling I've got some noise reject on as well I don't think that matters a huge amount but I've got a set to normal and I've just holding my tongue at the right angle and tweaking that trigger level and you know pretty much we can capture that and of course then zoom in on any of the detail we will sort of seen that a bit clearer on the analog type stuff but that is your high frequency noise and the rest of it is that low frequency content like that is your ripple and of course we can trigger on that ripple because we can go into our sauce for our triggering and we can trigger off the AC line there there we go that's the 50 Hertz so there you go it doesn't drift anymore so you know that is your ripple but of course that sort of line triggering of course only works for a linear power supply where you're going to get that 50 60 or 100 hundred and twenty Hertz ripple on the thing you're not going to be able to do that on a switch mode power supply which has a free running frequency for its switching convertor now this is our best possible single-ended test connection we can get for a bench power supply like this well what happens if you want to measure your own design or measure one of these little Brit converters or something like that let's take a quick look at that so to measure your own supply or a brick converter like this for example or something on any PC be switching bits which converter or linear for example you always take measure the output directly on the output filter capacitor like that I'm not sure exactly which one and here's here I'm presuming it's these in this big ceramic capacitor here so you'll put your scope probe directly across that capacitor with as low an inductance probing technique as possible so you might use one of your little low inductance ground spring clip adapters that you should have got with any decent set of scopes and you would probe it directly across there like that or as I've shown in previous videos you can actually solder a bit of you know dedicated wire on there like a little hook and loop so you can basically make one of these out of a wire soldered directly on the board and then stick your probe right in like that you want the lowest inductance path possible forget about using this garbage ah it's an antenna now I said this was the best single ended method possible and well by single-ended your scope probe is a single-ended probe ie it's got your input and a ground basically that is a single-ended test connection well that is not ideal because we still aren't 100% sure of the way of the noise noise on our scope is at common mode noise or is it actually coming out of the power supply the only way to be absolute sure and the best possible and recommended way to measure ripple and noise of any power supply is not to use a single-ended scope probe like this but to use a differential probe now you might be familiar with a high voltage differential probe like this lacroix a po3 one and these are fantastic to have and the tool for measuring high voltage stuff because they have differential input like this yes there's a positive and negative but it's a differential input not single men ended and it can tolerate high common mode voltages on the input but I'm and and it gives you a single ended output so it converts differential to single ended output that goes into your scope like this but this is actually useless for our task here because this is designed for high voltages it's not low noise and it only has a 1/10 or 1/100 attenuation so no good at all what you need is a proper differential probe and/or differential probe with a preamplifier on the input now the Ducks guts is one of these it's a lacroix has very high bandwidth higher than the 20 mega Hertz required but hey it cost thousands and thousands of dollars so pretty much is not much on the market in terms of proper differential probing for doing power supply measurements like this now there's a poor-man's way to do this but it actually works kind of reasonably well and gives you a good ballpark indication of whether or not you've got common mode noise or not and that's to use a the old technique over having using the dual channel of your scope and getting a differential measurement that way you'll notice I've got the 2 scope probes here but there is no ground connection at all it's just the center connection on both the positive and negative of our power supply so the grounds are not connected at all our Scylla scope of course is mains earth reference so we're going to get all sorts of crap coming from each channel but when you subtract one channel from the other bingo it should get rid of all that crap and give you a true differential measurement across there now the way to do this on an old-fashioned analog scope and a digital as well but I'll show your analog first we've got both our inputs here must both must be AC coupled both must be set to the exact same vertical attenuation range in this case I've got five millivolts per division I've pulled out my times five times ten magnifier so if five hundred micro volts per division channel 1 and channel 2 we're displaying we've got both channels active and we're inverting channel 2 that's important because an analog oscilloscope doesn't have a subtract function it's only got an ad function but if you have channel 1 plus the inverse of channel 2 that gives you subtraction so there we go we're on ad mode where channel 2 invert and as I said it's important that these two are exactly the same range otherwise if you've got that cow make sure your cows are just incorrectly otherwise it's going to be completely out of the shop and of course this is a big reason why this isn't a very good technique you don't get good common mode rejection ratio using these common mode rejection using this technique but it's good enough but look what what the hell is this what is this it's hopeless it doesn't work at all well the reason is we've got no ground connection between the scope and our system under test so it's picking up a whole bunch of common mode garbage on both these channels and it can't deal with it so we have to really knock that common mode stuff on the head by add in a couple of 50 ohm terminators on the input if your scope has 50 ohm termination turn it on so let's plug both our channels back in with I've got a series 50 ohm terminator on each one and bingo look at that we're now in subtract mode as I said if you muck around with any of the vertical settings if they're not completely matched like that you're just it's just not going to happen and of course if you don't invert channel 2 out you're screwed you're just looking at that and bingo we're getting bugger all there and you expect it to be bugger all because well the Rye goal is a very good power supply let's go over to a better example a much higher noise you know we can't go any further on a vertical let's go back to that horrible Manson switching power supply so there you go that's the test connection back on our Manson supply they're exactly the same load we had before and bingo look at that there we go there's our Manson power supply output there's some of the high frequency stuff in there we can actually turn our alt zoom on and we can actually see the zoomed value of that are zoomed part of that noise in there look at that so there's our ripple and there's our noise using our differential measurement on our analog scope like that and we should get exactly the same on the digital let's go back and try that and we're back on our wry goal here here's our channel 1 channel 2 input and I've got the math operator on a minus B there and as you can see it's a bit slow updating on the screen there but we're basically getting exactly the same waveform we get before with some high frequency content in there we weren't seen on our analog scope so what we'll do is we'll just expand that out a bit we'll go to our choir menu here and we're in normal acquisition at the moment we'll change that to our high-res mode with our Boxcar averaging and bingo look at that there we go we get exactly the same waveform or getting on that analog scope there on our digital scope but the waveform updating a little bit slow and that's one of the problems with the rygar scope and a lot of other scopes on the market they will do all that math function in you know processing in software so it takes usually time when you turn those math functions on that's why they're slow updating if we go to our Agilent 3000 series scope here it does all the math stuff and in direct Hardware on the ASIC so it is much better much quicker updating but the problem is this scope only goes down to 1 millivolt per division but it really only has a true 2 milli volt per division the 1 millivolt is actually just a software tweak so we get the greatest fidelity out of our waveform here so in that respect the Rygel scope with its true low noise 500 micro volt up front end much better for this purpose and here's an interesting thing to note what I'll do is I'll adjust the gain here on the scale of our math function we're currently at 1 millivolt per division there so I'll tweak that down here and you'll notice look at that you start if I go up 1 to 500 micro volts per division you start seeing the individual bits in there of the math calculation so this is you know one of the disadvantages of a digital scope and one of the advantages of the analog once you get down to with large differences and dynamic range you've only got that 8 bit converter in there to play with so really you know look you can start to see the individual individual bits they're just crazy look at that but hey at least we can see our waveform so that's pretty good and that value is going to change with our scale here if we turn our vertical up of course we get increased fidelity and resolution in that a calculated math value because it's only got those 8 bits to work with or more if it's the high-res mode but let's take it down to say 5 millivolts per division on both channels look at that totally blocky because it the signal the amplitude is down in the noise so it can only calculate look you've only got a couple of bits down in there ah bugger all so when you're using a digital scope just make sure you maximize the use of your dynamic range of your up front end by using the lowest a vertical scale possible and here's another trap for digital scopes as well there's our waveform what happens if we move ow one of our channels off outside the range of the ADC so it's clipping look look at that I'll calculate a math value just goes to complete garbage that's one of the advantages of analog scopes digital loo that that's awful real trap if you don't know what you're looking for but if you are observant you would have noticed that our amplitude here that we're getting is much lower than what we will get our differential way for me is much lower in value in amplitude then we'll get in with that single ended connection why we're still using x one probes here nothing's really changed we're subtracting one signal from the other we should get the same value but we're not remember look at our scale it's 500 micro volts per division here and it's basically I can go in there into the math function and adjust the tweak that up it's like you know two divisions sort of peak to peak there what we're getting before we're getting what about 10 millivolts peak to peak about 10 times more so what I've set up here in parallel is our single ended connection as well yeah you can do this ordinarily you wouldn't but we're going to get away with it here so we've got a single ended and our differential probe in it as well so I've got that yet the proper high frequency connection there it's going that third channel now single ended is going to our Agilent scope because our writing or scope is only two channels so let's have a look so there's the single ended measurement on our Agilent scope look two millivolts per division you know to four you know it's almost six sort of you know it's something like that hey yeah let's not dick around with the triggering and if we go up here and have a look at our differential measurement then as we said we're five hundred micro volts per division so we're barely even 1 millivolt their peak to peak so there's about a 6 odd times difference where is that coming from well if you remember a previous video I've done which I'll link in in that the how these oscilloscope probes work the coax cable isn't just a direct connection straight through it actually uses a lossy coax which means it has a resistance in it and we can actually measure that look let's get our multimeter here here we go and measure our center conductor which you'd expect to be a dead short it's not it's about 330 ohms ah ah we've got a 50 ohm terminator on our scope to get rid of all that crap and bingo we've got a voltage divider so if you work out how much the signals being divided time by well it's roughly seven and a half times with that 330 ohms and the 50 in there so that's why our amplitude on our differential measurement is so low so to get the true value that you're actually measuring you have to multiply that by the measured probe but in this case well you wouldn't be using scope pros for this measurement so I've actually another trap for young players is when you're doing this sort of stuff you wouldn't be using a scope probe like this is good enough to get an indication like this to see if there's any you know and get rid of any common mode noise or something like that but hey in this case it is not the correct method you should be using direct coax 50 ohm loaded so what we get down to is the ultimate correct method to do differential probing like this if you don't have a proper you know really expensive high impedance differential probe this is how you would do it you have your coax from the scope of course 50 ohm it terminated on the end here and you would have a 50 ohm source resistance in here as well and just to get rid of any DC out of there you would have AC coupling in both lines and that is that becomes your differential probe but with the 250 ohms in it you still got an attenuator so your final value that you're measuring hate you're still going to multiply it by two so there you go but that is how you would do proper differential measurement with a scope or with a preamplifier usually you would you know use the differential measurement into a preamplifier especially for doing something like the Reigle scope here which has noise we can't really measure you know with even with our 500 micro volts per division here it's just not really doable so you're typically you know whacking at times 10 preamplifier or something like that in there yes you could do this with two single-ended preamplifiers if you wanted to with your scope and stuff like that and you know that it still work but a proper differential amplifier like that lacroix one that's the one you want so there's no absolute requirement for actually having the 50 ohm termination here if you've got a proper differential art preamplifier there you high-impedance you know they'll be one Meg or 100 Meg or you know really high impedance and you don't have to do that but if you are going to turn on my turn terminate them like this like you do for a scope then well you're basically looking at you know transmission line stuff and supposed to match source and load impedances so you don't get reflections and things like that so if you are doing that yet proper 50 ohm source impedance and 50 ohm load over there is the way to do it and if you were doing this with the homebrew probe approach of course you would keep absolute minimum these paths in here you wouldn't have anything exposed so you'd have your coax is something like that you'd have your 50 ohm in series would be nicely heat shrunk and you'd have your tiny capacitor and you connect it directly across your bypass cap of your power supply to be measured but you know really that's just to do it yourself sort of a custom hack if you need to as I said by far the best way to do it is to use a proper differential probe preferably with a preamp for measuring our low noise power supplies like the ROI goal one we just did and here's the money shot you know how I told you that the reason we're doing this differential measurement is so that we can see if this noise that we're getting I'm single ended probing on back to my Rygel supply here so we get that really horrible noise on there those spikes we wanted to know if those spikes were actually coming out of our power supply well if we go up here and take a look at our differential measurement look we're probing the exact same point no look they're gone with the differential measurement they're not there at all so that noise is not coming from the power supply but if you're using that single-ended probing technique then hey you could be easily fooled into thinking that power supply was a lot noisier than what it actually is and if you're curious to know the frequency of that noise well it's around about a hundred and forty two odd Hertz between those with two spikes there in there so that's being picked up somewhere from something in this room hi I found the culprit it's part of the test setup check it out that's the way for me getting now and but look what I've done I've disconnected my electronic load and I've got connected stay resistive dummy load here similar amount of our current were taking two and a half amps instead of two amps but it's vanished bingo it's only when I use connect up my electronic load it's adding that switching there at 142 Hertz it's coming from this damn load so you've got to be careful of your test setup like this and where your noise is coming from and if we didn't use our differential probe in here to actually confirm that we would have thought for sure that it was coming from this row of house apply but it wasn't this thing's clean as a whistle and this thing is a culprit add in you know normally not an issue but when it's coupled in like this well it causes all sorts of stuff common mode so that's to do with the you know the design of it who knows where it's picking it up internally but it's definitely coming out of here and interfering with our test setup tada so there you go that's the basics of ripple and noise measurement for a power supply or maybe even one of these brit converters or your circuit or whatever like that and we've looked at single ended probiem we've looked at common mode noise we've looked at differential probiem we've looked at you know secret attenuation in your CRO probe CRO cathode ray oscilloscope probe that's what we call them here in Australia anyway yeah your scope probe and all there's lots of traps for young players there's a lot of art which goes into actually getting it real proper measurements on these things and knowing exactly what you're doing and not being fooled especially by common mode noise just because you see it on your scope doesn't mean it's actually coming from your device under test so anyway I probably there's some stuff I haven't covered in there as well and yeah there's a lot of around to try and do this right but I hope you learn something there and if you like the video please give it a big thumbs up beauty and if you want to sit jump on over to the EUV blog forum that's a place to do it link is down below catch you next time you you

Channel: EEVblog

Views: 242,552

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Keywords: ripple and noise, measurement, noise measurement, oscilloscope probe, psu, power supply, lab supply, bench supply, single ended, differential probe, how to, coax cable, common mode noise, oscilloscope, Ripple, Power, electronic load, Effect, specification

Id: Edel3eduRj4

Length: 37min 43sec (2263 seconds)

Published: Thu Mar 20 2014