Hi. This is the humble oscilloscope probe switchable times 1 times 10 that you no doubt got with your uh, low end scope. And this well might be all you'll ever need in terms of oscilloscope probing, but there's a more likely than not you're going to need at one point another type of oscilloscope probe for different purposes. And that's what we're going to take a look at in today's video because I have.

Check it out. Not one, not two, not three, not four, not five, not six, but Seven different types of oscilloscope probes. Actually, technically eight. and we're going to look at each individual one.

the pros and cons and what they're used for. Let's go now. Obviously, with so many Uh probes, I'm going to have to keep this relatively brief. And I do have uh, in-depth videos on, uh, many of these different types of probes.

so I'll link this in now. I'll cover each one, uh, separately. but let's just have a quick look. Uh, the first three we've got here are all, uh, passive Pros: We've got our 10 to one switchable uh probe, We've got our fixed uh times 10 probe.

you can get it in different attenuations you know, times 10 is your most our standard And then we've got a simple uh, coax based one. But believe it or not, ah, these three are actually pretty much in our performance order, with the uh switchable, tender one probe being uh, the lowest performance, the uh, traditional times 10 being like pretty darn good performance. but your coax can actually be technically higher performance and we'll go into why. Anyway, these are what are called passive probes because they contain no active circuitry at all.

They might have some compensation uh, trimmer capacitors and resistors in them, but basically no active electronics and then we'll take a look at uh, active probes. I've got three different active probes here in the lab, so we'll take a decent look at those. These are our better performance once again, but this will actually contain active fit amplifiers inside the probe itself. But those four are your basic for oscilloscope probes.

Now we have to get into the more specialized probes. We've got a high voltage differential probe, we've got a current traditional clamp current probe like this, We've got a positional current probe which is a real interesting, uh beast. and then we have H field or magnetic field and E field or electric field. uh, pros which I've also covered in other videos and I think I've pretty much covered most of these in dedicated videos, but that's what this video is about.

We're going to cover them all fairly briefly, so you know what's what. You know it, you love it. The switchable times: 1 times 10 Oscilloscope probe which has a switch on it, which of course has times 1 and times 10. But it's a little bit misleading because it doesn't actually multiply.

it actually divides by 10. It's a divide by 10 Attenuator times 1 is just, uh, basically straight through. and because your oscilloscope has a one Meg input impedance, that means in times One mode, this R probe has a one Meg Dc input impedance. but when you switch it to times ten mode, it puts a nine Meg resistor in series with that, uh, giving you a nominal 10 Meg input impedance on your one Meg scope.

So these are probes are really good for you know, uh, lightly loading a a circuit, a Dc circuit, that is. We've got to get into Ac and they come standard with your antenna, ground connection like this, and of course your easy hook for probing in your circuit or you take that off. And of course you can just probe like that. But I mentioned antenna earthly because these add inductance to your probe so they almost always come with a little don't stab yourself Dave High Frequency probe attaching ground probe attachment because that's your ground and that's your probe and this is what you use for your high frequency Uh probing technique.

Only really applicable on Times 10 because in Times 10 mode, you get the full rate of bandwidth. in this case, 350 megahertz. Which is pretty much where are these switchable probes actually? Uh, stop. But yeah, you know your more familiar ones will be 100 200 megahertz.

They usually supply, uh, the same bandwidth as what scope you've got and they come in two different styles: one that has the high frequency compensation adjustment up here on the Uh probe and the other type has it down on the base here. Usually your higher frequency ones have it. Uh, down there, it's neither here nor there. does the same job.

And for all these types of passive probes, you want to compensate them. and you do that by hooking up your probe in Times 10 mode. doesn't do anything in times One because the compensation cap is for that nine Meg resistor in there for the times 10 mode. hook it up to your compensation output, which just generates a one kilohertz uh, square wave.

That's it. And then you, uh, use the adjustment tool provider, which is a non-conductive one. You don't want to use a conductive one and hold your tongue at the right angle and you trim that until you get a nice, beautiful, even square wave like that. Good enough for Australia.

So what you're basically doing there is, uh, tweaking the capacitor across that nine meg resistor in the front of the probe, Uh, to the input capacitance of the oscilloscope which is usually around about 15. uh, picofarads, 15 puff give or take. And the thing you have to understand with these is that, yeah, in X 10 mode, you'll get your rate of 350 megahertz bandwidth or whatever it is. But you put in times one, you're gonna get well under 10 megahertz.

but don't take my word for it. Rtfm one to one attenuation mode Dc to 6 megahertz bandwidth rise time of 58 nanoseconds, and in Times 10 mode, you get the full bandwidth of the rise time of 1 nanosecond. Why is it so well? I've done an entire video explaining why the bandwidth is lower on times One, and these probes are typically rated like 300 volts in Times 10 mode. So they're You know, they're pretty decent.

But what you may not know Rtfm again, is that the high voltage performance is very poor. with frequency. it just drops off. Look at this: 10: 20, 30, 40, about 40 Kilohertz.

This particular probe, it's voltage rating. Uh yeah, 500 volt rating. But it just drops off, drops off, drops off. So if you want to get the full 350 megahertz bandwidth somewhere here, and its voltage rating is enough.

All so the pros for these. Well, you've almost certainly got it came with your scope. They're very, uh, cheap. You can actually pay significant money for really good quality ones, but they're basically cheap and they've got pretty decent performance bandwidth on Times 10 mode.

and they're just the most versatile. Uh, probe. Really, it's all in one you put in Times One mode when you want to do like you know, measuring low level signals and things like that. and you can't afford the Times 10 attenuation if you're trying to measure like a a five millivolt signal for example, and you whack it in Times Ten mode.

Well, that's going to be 500 micro volts at the input to your scope and well, that's not great so you want it in times one mode. But the cons for these things, well, there's quite a few of them are One is you're guaranteed absolutely guaranteed to come a guts up with the times 1 times 10 switch and the setting on your scope because if you want the voltage multiplication factor to be correct on the screen, you have to make sure times 1 or x 10 matches the setting in your oscilloscope and these do not come with a little pin on them to like auto detect the probe. So you have to set it manually and Murphy will guarantee that you will have it set wrong and you'll be out by an order of magnitude and your voltage measurements at the worst possible and most frustrating time. But hey, there is a reason why these are supplied with almost every like low-ish end oscilloscope.

because they're versatile. just you know. They have a few downsides though, which is why we're looking at the next probe. Our next probe is the fixed times 10 probe and this is usually are the default probes supplied with higher bandwidth, more expensive oscilloscopes.

Why? Because well, without the switch in the handle like this, you can optimize, uh, the performance of these things. There is an art and science to oscilloscope probe design. You can make them higher bandwidth. In this case, here we've got 500 megahertz and it's uh, of course, the same uh, 10 mega ohm input impedance.

It's got the same nine meg resistor in here. It's designed to match a one meg input on your oscilloscope. Voltage rating is still pretty much the same. It's yeah, it's practically identical.

it just doesn't have that times one switch position. But what it does have is a little pin on there which is an auto detect uh system so that when you plug it in your oscilloscope. Uh well. most decent high end scopes will have an auto probe detection ring around them like that, so there's a little uh resistor in there.

so when you plug that on there, it makes contact and the scope knows it's times 10. So we're on 50 millivolts per division At the moment. when we plug this probe in like this, it automatically detects and goes to 500 millivolts per division. Brilliant.

You can't come at the guts up, Murphy's not going to get you with these probes. and they also come with a compensation adjustment down the bottom here. Sometimes they might have a high frequency adjustment as well, but these passive probe designs can go higher than that. This is, I believe.

Correct me if I'm wrong, the highest bandwidth passive probe on the market. The Tektronix Tpp 1000. It's a one gig probe. Look at that.

Once again, 300 volt rated Exactly the same 10 meg input impedance, but it's got lower input capacitance. 3.9 picofarads. We'll talk about that later on in the video and these things aren't cheap. This probe costs about 800 bucks each, so for my mind, these are the best bet.

Uh, especially if you're working on high frequency stuff. but just the best for everyday use because uh, most of the time you're not going to use that times one uh switch. So just having a nice, uh, fixed times 10 probe that's automatically detected by your scope and your settings okay and like you're not going to come a gutsy with these. But of course the one common with this is that well, for low voltage level work, the times 10 is a bit annoying, but hey, just keep it switchable.

A cheaper switchable probe for backup, and for your 800 bucks, you're actually going to get a lot of value in this. You're not only going to get the one gig bandwidth, but you're going to also get the integration with the scope. In this case, it's the Tektronix Mdo 3000 so if I plug that in, watch this over here. You might hear a relay click.

There it is termination set by Tpp 1000 probe so it knows don't turn on any of that 50 ohm uh termination rubbish. And the probe set up here. it's automatically detected. uh the serial number.

It knows it's uh, times 10. So if I hook my probe up to the compensation pin, I can compensate probe for channel one compensate probe and it'll go and do its business. It'll compensate. you don't have to muck around with any little uh, tweak adjustments with your tongue at the right angle.

And now it's matched that compensation setting with that probe. So now it has that setting in there. and if we plug that probe in, it knows that it's compensated. We've already compensated that probe with this channel, so if we plug that actually into Channel 2 over here, it'll no.

aha. It's now default compensation that is not compensated. So it knows that we didn't compensate this probe on this channel now. Brilliant! and just a quickie which I didn't include at the start of this.

And ten to one probes aren't the only ones you can get. You can actually get higher ones designed for higher voltages. This is a cheap generica cheap about 50 bucks p2300c. It's a hundred to one probe, so it's got a nominal hundred mega ohms input impedance, which means it's going to have a 99 meg resistor in here instead of the nine meg in your uh, ten to one probe.

So this is a 300 megahertz job. These go up to like 500 megahertz and this is five kilovolts Dc plus Acp. I've done a video on how not to blow up your oscilloscope and we'll see that in a minute with our differential probes, but these are just single-ended uh probes just like your regulars. So it's going to be Mains Earth Reference when you plug it into scope.

It's got uh, the extra little uh protection around there so you can't touchy the uh frame. and these are of course, a great option for portable scopes like this because they're not battery powered, not Mains Earth Reference. And uh, often they're going to have the isolated channels. So yeah, well worth having one of these even for your normal scope.

Just you know, when you want to measure 500 volts, you can't do that with your regular probe. So this is where these come in. So unfortunately, just like the uh, tender One probe, these aren't uh, magic. You won't get the full 300 megahertz uh bandwidth at the five kilovolts nowhere near it.

It will have a D rating curve which will look like this except it will have a you know, a higher voltage it might have you know, like 500 volts here or something out at like you know, tens of megahertz or something like that. So it's still going to have the D rating, but it's going to be a lot better than the tender one. So basically the same as your fixed times 10 probe. unfortunately.

uh, this one doesn't have the auto probe detect and you may be able to get one to actually match your particular oscilloscope that has like a different value resistor in there on the probe tip that it knows it's at times 100 in times of instead of a times 10. But you know, really? yeah, if you can, that's great, but it's probably going to cost you a fortune. These ones are, uh, pretty cheap. And the good thing is well, they're pretty decent bandwidth and the hundred Meg Ohms um, Dc input impedance is great for really high impedance.

uh circuits you might be measuring, you know, a crystal oscillator or something like that. You really don't that has like, you know, Meg Ohms sort of resistors in it. You don't really want to load that down, so this is a great way to do it. although you get higher attenuation, but if you can still see the signal beauty.

so definitely well worth having. Like in just a cheap generic one of these in your kit just in case you need high voltage or high impedance. So if you can't afford this, uh, expensive one gig probe? well you can make your own. Here's our next type.

Still a passive Uh probe, but it's a bit of coax with a resistor in it. You can make this for a couple of bucks and believe it or not, this will actually perform as good or better in terms of uh, signal fidelity than that expensive. 800.1 gig probe. How is it so? Well, this is actually called a under many names.

it's called like a transmission line probe, a resistive probe, a Zed Naught or zero probe. And basically what it is is it's a bit of coax rg174 for those playing along at home with terminating a standard B and C. And in the end, here it's just got is simply a 1k series resistor and the braid just goes off here to your ground tip. And that's it.

A 1k series resistor in a coax. How can this perform as good as like a multi thousand dollar probe? even? Well, there's a bit of art and science to it, and they can basically, uh, match the at least signal integrity. uh, performance of like a multi thousand dollar, even ten thousand dollar, ten gigahertz probe if you do these right. But yeah, there's a lot of art and science in getting it right.

and this one here, I just, uh, crudely made up. I haven't measured its performance once again. if you actually want to characterize the performance of it and no, it's going to be good, then, well, you need all the gear and the experience to do that. But I have no doubt that even this simple one I just lashed together is probably as good in terms of signal fidelity as you know this 500 meg Agilent.

not another keysight rubbish. Uh, probe here. Okay Dave, what's the catch? If anyone can just start lasher probe like this together for practically zero cost, then why bother with like expensive, high bandwidth probes like these ones? Well, the first thing is is of course that gorgeous input impedance that 10 meg. Ohms.

Um, at Dc. By the way, we'll get into that uh input impedance and well, you know it doesn't load down your circuit much at Dc, But unfortunately, this puppy with a 1k resistor in series, these of course have to be terminated because this is a transmission line. and if you don't terminate the other end, you're going to get reflections galore. And it's just.

well, it's not going to work as a probe, so you have to have a 50 amp termination on your oscilloscope either internal uh, to the scope, or just an inline one that you actually plug in. and if you run the numbers, put that into confusor. Then with a 1k in series with a 50 ohm termination at the other end, you're talking about a 21 to 1 ratio as opposed to a 10 to 1 probe. This is a 21 to 1 or 1 to 21.

so it divides your signal by 21 times and you've got a 1k uh Dc impedance so that loads your line down substantially. And of course, you don't need a 1k uh resistor in here in series. you can basically make it any value you want, make it larger or smaller, and you can have it. Um, of course, if you put in a 450 ohm resistor, then you'd have the same 10 to 1 probe as you would here.

But the difference is. um, instead of having a 10 meg input impedance here, this one would Have a 500 ohm input impedance and that's going to load down your lines at Dc. But the interesting thing is that uh, this is 11 puff, 11 picofarads here, and at frequency, that is going to load down quite substantially. So now we actually have to talk about uh, probe loading.

Whereas this is not going to have much capacitance at all. So hence why In theory, you know if you use right coax and everything else you can get, you know 10 gig bandwidth or something, many gigahertz bandwidth out of these sorts of probes if you construct them right and terminate them right and all the rest. So what we have to look at with all of the passive probes we've looked at is probe capacitance and it's either written on there or it's in the data sheet. in this case, 500 megahertz probe.

It's got 11 puffs, 11 picofarads. Uh, basically input comparisons, a capacitance, and it's sometimes called our total system Uh, capacitance because it's basically the capacitance as seen when this thing's plugged into oscilloscope and the total Uh system installed. So this one is 11 picofarads. That's what your circuit is going to see.

so that actually loads down your circuit. So that 10 meg input impedance? Yeah, that's a Dc, but you've got to talk about in terms of capacitive reactance and this is your standard formula, which you should know the capacitive reactants or I think of it as Ac resistance of the capacitor is one over two Pi F C. So you plug the numbers in. say for this, Uh, Agilent? Uh probe here.

500 megahertz for 11 picofarads. Um, basically you're presenting a 29 ohm load to your circuit. So instead of 10 Meg, your circuit sees 29 ohms at 500 megahertz. So yeah, as you can see, it's very low impedance.

so at the full rate of bandwidth. The approach. There's not really much difference in loading between. uh, like a 10 meg passive probe like this and these um, resistive probes that you do it yourself like this, even if you have to load it with, uh, like a 50 ohm termination on here.

So let's take this magic 800 r one gig band with passive probe here. plug the numbers in one gig. 3.9 Uh puff. It's like a really low capacitance probe.

The higher bandwidth you go, the lower capacitance you're going to need. it's still around 41 ohms and resistance on your probe. So that's going to load down your circuit. So these resistors probes will also load down your circuit.

but at their worst at Dc. As I said, this will be a load it down with 1k total or whatever series resistor you decide to put in here. And of course you could have no resistor in here. You could just feed it straight in.

but then you're going to come a gutser because you're going to have this cable is actually high. uh, capacitance? Because this cable, you know it might be like a hundred, uh, picofarads per meter kind of ballpark. Uh, figure. And you plug the numbers in.

It's a hundred puff at one gig. two times Pi times one gig times a hundred puff equals invert. Um, yeah, uh. 1.6 Ohms anyone? Um, so that's why there's a resistor in series.

With this, it just helps isolate, uh, the capacitance of this probe and this probe with a 1k resistor in series. That's kind of like a typical value everyone uses. It's not too high, it's not too low, it's just right. It's like the Goldilocks uh, value.

And this probe is only going to have like, you know, one or two puffs. although I haven't measured this one. Probably going to be better than this real expensive 800 probe here at one gig. So there has to be another downside to this.

And yeah, there could be. um, if you choose, like the 1k value in here, you've got that oddball 21 to 1, uh, divider ratio instead of your more standard tender one. So even a real, like, you know high end expensive scope like this Tektronix Mdo 3000 one gig bandwidth up here. Um, check out the probe attenuation there.

It's one two five ten. Well, we can get 20. We can get close, but we can't get that 21. So not many scopes are going to have the ability to add like a custom value in there, although some might.

So if you use that oddball value, then, well, you either have to just set it to one times one and then just do the calculations manually or you can, uh, choose the resistor value to match so you can get an E 96 value resistor like just over 950. Ohms, That'll give you a reasonable like a 20, uh to one ratio. But one other advantage of these is that, uh, they're actually slightly more tolerant of longer ground leads than a Fet pro, so that's a benefit. So you know these things, if done right, are really, very, very good.

Okay, let's give you a probing example here. We've got a Raspberry Pi 3 for those, uh, playing along at home and we're going to probe one of the memory pins on the bottom here. I don't care which one, I've just picked one at random, we're getting a signal on it. so I'm using the two gigahertz active probe here.

The N2796 Overkill for what we're doing. Well, overkill for this scope anyway, because this is a 500 megahertz bandwidth scope. So here it is. I've got my little adapter careful because you can stab yourself with these little bastards now.

Ground pin which can sort of like, you know, pivot around like that and anyway, that will make better contact and this will be a higher frequency probe because it's a shorter inductive path will require the tongue at the right angle and probably some magnification here. Okay, I've got my ground point and I've got my probe point. single shot capture that. See if we can get it? No.

There we go. got it. This is the loading of the line with a one picofarad one puff active pro which costs a couple of thousand dollars. Let's compare Dave's dodgy, um, homemade, uh resistive probe here with a 1k resistor in the tip.

We'll give that a bill. Got a 50 Ohm uh. terminate that, but scope can do that. No worries.

Turn at the right angle, tongue at the right angle. Fix that. Oh, check this out. This is absolutely fan freaking tastic.

Signal integrity is excellent. Let's let's take a look at this. Actually, if you have a look at the bottom here, you can see that both of them undershoot Almost exactly the same. But you remember how I said that the resistive probe can actually be more tolerant of longer ground leads? I think they're both about the same length? I think they're practically near identical.

Remember how I said uh, it can be more tolerant on these than active, uh, fet probes? This might be an example of this because this is not a you know, this is not some controlled experiment. this is just something I you know slapped together willy nilly and um, this is the result that we actually got. This is fascinating, right? They both undershoot exactly the same, but the active fit probe the orange one actually look. It overshoots again when, and so, and it takes much longer to recover than the resistive probe.

Look at that. So this could be an example of where this cheap ass do-it-yourself resistive probe is actually outperforming this two and a half thousand dollar active fet probe in terms of signal integrity. But once again, this is not a completely controlled experiment. but this is what you can actually get.

But of course the limitation is that it loads it down much more 1k as opposed to one meg, right? There's a huge difference there, and you might know. Oh, what's the difference between this? uh, load? You know, look, it's it's dropping with the 1k. Is that the effect of the 1k load over here? Well, it's actually not if we actually, uh, measure that because you remember, um, it's a divide by 21 probe as opposed to the active fit probe which was divided by 10.. So if we actually, uh, set up our cursors here and go, I've set them precisely to the same ground point.

Here our resistive probe is we're getting 55 millivolts there. So if you get your confuser out, 55 millivolts times 21 which is our probe 1.155 volts. and this is a looks like it's a 1.2 volt bus so it's like it could like it's maybe 50 millivolts under, but we have to measure the other one actually. And of course the choice of resistor value is always going to be a trade-off.

Like if you go higher and higher in resistance, then your divider ratio gets higher and higher and higher. and you can't measure low level signals. and it's not that great. But the higher value in resistor you go, the more you can isolate the cable and system capacitance from the tip.

So technically you know the less you're loading your circuit. But yeah, it's all a big trade-off and I actually uh, showed one of these at the start which is just a B and C to a crocodile clip. You can get B and C to easy hooks, you can get B and C to banana plugs, and they're quite common for liking just plugging into systems. But you have to be very, very careful with how you use these, especially at high frequency.

Because these are a transmission line, they're actually called a transmission line probe for a reason. Which means that if you just hook uh something like this up uh to a high frequency signal that you're trying to measure and you don't terminate it correctly because this is a 50 ohm impedance. uh, coax. If you don't terminate it correctly either at the Uh source or at the or at the oscilloscope end in 50 ohms, then you're going to get reflections on this.

and I've done a whole video on this how I actually goof this up. but I'll give you a quick demo again. Let's say, you want to measure the switching noise of a power supply here. Very simple application.

relatively low frequency. You do it over 20 megahertz bandwidth. which is why you want to enable, uh, your 20 megahertz bandwidth limit on your oscilloscope. That's just an industry uh.

definition of uh, power supply noise over that bandwidth. And so you might think, okay, this is a really low impedance source. It's a power supply. And how can you possibly go wrong connecting your scope directly up to here? You've set your probe to one to one.

Bingo. There's your power supply noise. You're measuring it. It's you know, 400 millivolts, Something like that.

Well, you've come a Gaza. So check this out. Okay, here's our noise with uh, our just our direct coax actually connected, uh, straight through. But let's change this to our switchable, uh, 10 to one probe.

Let's put it on times One mode. Okay, so there's no resistor in the input probe here. It's basically just a coax going into the scope, right? It should be identical to this. Well, let's change nothing.

and let's plug it in. Look at that. 10 millivolts, peak to peak or something like that. As opposed to this, like 400 millivolts, we're out by orders of magnitude.

What the heck is going on here? Well, I've done a whole video on this. as I said, but and kind of a bit of a spoiler alert here in my uh, Secrets of Times One Oscilloscope probes. I show that this isn't just an ordinary coax like this one is. and it all has to do with termination and transmission line reflections with just this, uh, dodgy bit of coax with no termination here or at the front end, Then we're getting reflections on that cable and it's taking one little tiny pulse in there And it's oh, it's getting reflections always.

That's why it's looking absolutely horrible. These are signal reflections on your transmission line, even with a 20 megahertz bandwidth. So yeah, you can really come a gutser just using direct coax. Beware.

So to show you the effect of this, this is the direct connection with the coax and if we put a series resistor in front of it, which is a series termination resistor, bingo, it's gone. Anyway, I've done a whole video explaining this, so just beware with ordinary coaxes. They aren't the same as a Times One probe. so I hope you enjoyed that video on passive oscilloscope probes as they're called.

And I'll link in all of uh, the videos related to passive probes because I've done quite a few. But in Part Two of this video which you'll have to check out, we're going to look at Active Pros: various different types of active Uh probes fed active probes, differential probes, current pros, positional current probes, and stuff like that. So really interesting stuff, so I hope you found that useful If you did, please give it a big a thumbs up. As always, you can discuss down below on the Eev blog forum and check out my alternative channels and all that sort of jazz.

Catch you next time you.