Hi In the previous video linkedin at the end and down below. if you haven't seen it and you must watch it because this is part Two. We looked at uh, four different passive oscilloscope uh probes, the switchable one to ten probe, the fixed times ten, the high voltage probe, and the transmission line resistive probe. And these were all passive probes.

But now in this video, we're going to take a look at what pretty much can be called all active Pros because they contain some sort of active amplifier circuitry. Our first one we've got is the High Voltage Differential Probe. This is the Evblog Hvp70. It's a 70 megahertz high voltage differential probe.

It's uh, designed for measuring like a thousand volts Rms max. You might think, well, this one can do five kilovolts and this one only does a thousand volts. What's the difference? Well, you remember I said this is Mains Earth Reference and I've done that video on how not to blow up your oscilloscope. You cannot use one of these or you can't use one of your other pros because if you hook your ground point up, that is like connecting Mains Earth to any point on the circuit that you connect this through and you can come a gutter and you can blow up your product, your board.

Whatever, you can even blow up your oscilloscope. You blow up your leads. You can really have a bad day. So unless the ground of your product is actually isolated from Maine's earth, you can't just go sticking this ground probe willy-nilly anywhere in your circuit because you can cut my guts up.

And things like you know, main switching, power supplies, or other things they're of course you know, Mains Earth Reference. So um, yeah, you plug this on the wrong point and it's just going to vaporize. But what the high voltage differential probe does is let's lets you safely put either of the ground or the positive lead anywhere in your circuit. Well as long as what the maximum his is here.

a thousand volts rms and your common mode which is that connected through the ground plus minus 700 volts. Good enough for any like you know main Switch Mode power supply. You can just connect your probes up to anywhere and you're going to be completely safe. You're not going to blow up your circuit.

You're not going to blow up yourself. You're not going to blow up anything. These are great high voltage differential probes. Okay, just a quick recap with Dave Cad here on what Uh, this common mode of voltage actually means.

Well, This high voltage differential probe. It basically is just a differential amplifier. It's just an amplifier like this that measures the voltage difference between the positive and negative input terminals like this. and then it multiplies it by amplifies it by a gain of 10 or 100 depending on where you are set the switch and then it just goes out to the B and C here to your oscilloscope.

And of course the oscilloscope is going to be Mains Earth to reference. So what? This voltage here? 1000 volts Rms maximum between the two terminals. Here it's exactly as it says it says you can have up to a maximum of a thousand volts rms or basically, uh, the linear range, uh, the measurement range plus minus 700 volts Uh, between these terminals Either directions. So good enough for like mains measurement and things like that.

and you can get higher voltage versions of these which go much higher. I think this is actually one of the, uh, lowest voltage ones on the market with that times 10 times 100 and we might explain why in a minute. Anyway, common mode voltage what that means is that between either of these inputs here either one positive or negative and this output, its output referenced and the output is of course going to your oscilloscope which is Mains Earth reference so that's connected through to your mains, which then could be connected back through your powerpoint through to your product. And I've done that whole video on how not to blow up your oscilloscope so I won't, uh, recover all that.

But basically this pro can handle up to plus minus 700 volts between. This is a voltage source here. between either of these terminals and the output, mains Earth are referenced here. This is why you can, pretty much, um, for most are practical circuits that are Mains powered or lower voltage.

You can connect your two probes up to any point in your circuit and you're not going to blow up anything. You're safe to measure any point in your circuit so you could measure across. You know, like a shunt resistor in there or something like that to get the current waveform or whatever it is. Now here's a reverse engineered Dave Cad drawing of a similar model to this one from the manufacturer.

uh, Sapphire. This one will be exactly the same. Just uh, some white and just some performance starts week differences. This is how these high voltage differential probes work.

And there's a big common misconception about are these high voltage differential probes. People think that they're actually isolated, that the Uh inputs are somehow you know, transform or other isolated from the input. Well, that is not the case. All these things do is actually contain large value input resistors.

In this case, it actually tells you down here. Read it. Four meg each side to ground and 5.5 puff and that's exactly what you get. You get four one meg resistors, Two ground.

Here's the ground terminal. Here is the output. uh, the reference. I haven't drawn it, but output ground over here like this.

and this comes from my uh, reverse engineering drawing. so I'll link that one in. But basically yeah, that is connected through to here. So it's look it there it is.

It's connected right through a four meg resistor and they've got a low value down here. 25. so it's just a resistor divider in each leg. and then they've got a Fet differential amplifier here and some extra gain stage times 10 times 100 selected and that's it.

That's all that's inside one of these things. But because they've got such high value resistors, you can plug them anywhere in your circuit and it's not going to cause a problem. But of course, it could potentially load down your circuit if it's a really high impedance circuit of course. But that's the same with any probe.

These things don't really perform as good as a proper oscilloscope one. this is only uh 7 megahertz bandwidth and with these long leads on the input, okay, you've got to twist them to get even half. Decent, uh, performance. And yeah, they're just not as good at performance as proper oscilloscope probes.

But they're incredibly safe and that's the reason that you want to use one of these and you can probe any point in your circuit using a ground referenced oscilloscope. They're just like they can't be beat. But the downside is is that because they have to have such large resistor divider ratios in order to be safe, then, well, they're not great for low level measurements, which is why you won't find a high voltage jar dip. which is why they're called high voltage differential probes.

you won't find a well. There are some low voltage differential probes, but like, yeah, they're generally high voltage because they have to have a huge divider ratio like that and these are either battery powered In this case of this one are four double A batteries in the back or you can power them because the power is output reference. You can actually power them from the Usb port on your scope. Here if you've got an adapter cable and now next probe.

Guaranteed to get every engineer all excited. Oh that's the Active Fit probe and they always come in impressive cases like this and this and this, right? You never, just, uh, get like a little like probe in a packet would ever know. They always come in beautiful cases like these. Let's take a look at them.

So here's a very typical active probe or the active fet probe or just Fet Pro because they've all got uh fets right at the input here that actually uh, amplify the signal before it comes in. So they have active amplifier electronics inside the head as opposed to your passive probe here which is just a basically a bit of a resistor and a bit of coax and the amplifier is inside the scope. Well, in this case, the amplifier is up here which means they have to actually be supplied by power and it's very common for them to actually be powered from the oscilloscope under test. And look at these lovely little pogo pins and you usually buy them from other manufacturer of the oscilloscope because they've got their own interface.

This one is your agilent uh, keysight. So those probes are not only give it power, but they also, you know, tell it what type of probe it is And and things like that, your signal doesn't actually come out on these pins, this is just power and other data. Your signal of course goes into your input to your scope. so it's just that's a regular B and C, but it just plugs in, it's all captive, and they usually have a little lever in there to clamp on the front of your scope.

So these things are usually very pricey. You know they start in the four digit category and uh, go up to like five digits and this one here is a two gig bandwidth probe tender, one uh divider ratio, one meg uh input impedance and this uh signal one here active probe. It's A it's one gig uh with one mega ohm and uh 1.2 picofarads. Uh, but you might think well, okay, this is one gig.

Well, so is this what's the difference? Well, the difference is. remember, this is like practically the world's best passive probe. 3.9 puff. This one 1.2 puff and that's the difference.

You remember our formula before. capacitance is the thing that matters at high frequency. And in the case of this uh, sigilent active probe compared to this Tektronix one, both are one gig rated probes. But because it's only 1.2 uh puff, it's 132 ohms at one gig.

whereas the passive probe is 40 ohms at one gig. So that can make a heck of a difference to the signal that you're actually measuring that low that load is going on the line that you're trying to probe. So the lower the capacitance, the less you're going to load your line. But if you are talking Dc, then the passive probe is still better.

That's 10 mega Dc. These are only a meg. so you use an active fet probe over your passive probe. When signal integrity at high frequency really matters, well, I these can go higher.

This is actually the fastest uh passing tender One uh, passive probe you can get at uh, 10 meg. This, and as I said, um, this thing with a resistor will you know if you build it right will actually outperform this and these can actually go up to 10 gig. So yeah. anyway, so the only solution basically for above one gig measurement is either an active fet probe or a resistive probe.

That's it. And if you're wondering this agilent one is one puff input capacitance and this one here haven't measured it, but it'll like it. probably on beyond par. Something like that in the order of a puff, half a puff, maybe.

So the great thing about active fat probes is you, they can actually go beyond 10 gig and beyond the performance of a simple uh, resistive uh probe like this. So if you're on the bleeding edge of measurement, um, you're You're really going to be wanting an active Fet pro. So, pretty much as a ballpark, maybe anything over over 500 meg, you want to either be using active Fet probe or a properly, uh, built and characterized resistive probe. And like it can cost you more money to actually characterize, uh, this than to simply buy the already characterized active Fet pro.

And basically these single-ended active pros pretty much stop at a couple of gigahertz anything over that. Then you start talking a uh, fully differential probe but not high voltage like we looked at before. These would be low voltage, uh, differential probes, high speed, low voltage. But the one downside with these things is Murphy can get really expensive.

Like These probes can cost thousands of dollars even into the six digit range. And their huge achilles heel is the maximum input voltage. in this case, max input 20 volts peak. Okay, seriously, you go over that and this probe will blow up.

You'll probably find ebay's filled with like, oh, this Fet probe Um, yeah. Sold. as is. I would not be buying a sold as is Perfect probe off Ebay.

Just saying. We've got one from uh, Caltech Electronics here. This one's a little bit more robust. We're talking a 40 volts peak.

Here's a 1.2 gig probe once again, 10 to 1. this one's higher input capacitance though. Three puffs. but as you can see, um, this one you can get like generic ones.

You don't have to get these ones designed for your specific scope. Uh, you can get these cheaper ones um that just plug into your like any scope and they're just actively powered once again. Uh, from just the Usb port on the front of your scope. Nice.

And as I showed before, these things always come with. like all these accessories, let's take a look at them because they're very interesting. So these are the ones that come with the Caltech probes. You've got beautiful little ultra tiny mini grabbers there.

you've got little uh, ground and uh probe pins like that spare ones because you're going to be using them all the time. Plus, you've got like little uh pins like that. They can plug into headers and often on your designs. When you're if you know you're going to be probing like you're really serious designs.

maybe on a prototype board, you don't necessarily need it on a production uh layout, but on a prototype board, you're trying to get it working. You're measuring your high speed uh, Ddr bus or whatever. Then you might have a dedicated test points on there. even dedicated connectors for these high speed pros and the signal ones.

Once again, you get all these uh, like spare tips because you're gonna get going through them like there's no tomorrow. You might even want to directly solder the tips into your circuit so that you can physically, uh, remove your probes. The most interesting kit comes with the keysight one. Once again, you've got a little tube with all the little pins in there.

geez they don't give you many do they? A bit of a tight-ass real expensive probe, yet ultra tiny mini grabbers. Once again, like these things are just super super tiny and then you like plug into there and give you all sorts of other little uh adapters like that. Um and the most interesting thing is they give you uh copper pads like this and they actually give you a bit of a chart here on you know some of the different uh probe connection techniques and this is not the video to go into. really high frequency uh probing techniques of course.

but you can look. You can plug directly into the head with some long leads like that and that'll give like you know, 500 meg bandwidth. Here they're saying or uh, you know you can get a rigid probe tip with offset ground like that so it plugs in and I love this keysight head. It's got little Leds on there that just light up so you can see where you're actually plugging your probe into.

very nice. and then you've got a spring tip with ground blade like this. uh and that'll give you like two gig bandwidth. and then you've got a copper pad which you can solder onto your circuit and that will give you like a flexible ground point.

So you know often it's very difficult to apply pressure to like both of these points at the same time without one of them sliding around. Well if you solder in like a large ground pad like like with that copper tape that they are supply then you know you don't have to worry about your ground probe sliding around or you do have to keep an eye on it because Murphy's ensure to slide off and short out one of your other pin on your expensive hundred thousand dollar prototype board. Trust me, I've worked on hundred thousand dollar prototype boards and if you blew that up, yeah you're gonna be having a bad day, but once again you know that might be a slightly reduced bandwidth to you know this technique over here which is going to provide a lower inductance uh path so it's going to you know you're going to get better performance out of it something like that. and then you just got you know if you want to put just pin headers on your board for various test signals and then little short cables which run over and just plug into your probe tip.

So all these different uh solutions for probing and you can even invent your own. And as I said a lot of designers will solder on like like coax connectors directly onto the board and things like that so you can plug on your own probes, your own, resistive probes, or active fat probes or whatever it is you're doing so. Active effect probes. You can think of those as the Rolls-royce of oscilloscope probes.

Really, they're very nice, but as I said, you know, roll your own with a bit of Rg 174 coax and well, you can get similar performance if you do it well enough. But oh yeah, these can't be beat if you've got the money. And these pros will usually require 50 ohm termination on your scope. Although this a cow test one here, it actually, well.

it comes with a 50 ohm uh terminal look at that. 2gig 50 Ohm series inline terminator 2 watts Oh, that's very nice, but this one actually lets you use it with a one Meg input impedance scope Just so you know, 50 ohm termination and it gives you an actual attentionation setting of five times. So that's you know better for like, low signal measurements. Nice.

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 uh probe here.

The N2796 overkill for what we're doing Will overkill for this scope anyway, because this is a 500 megahertz bandwidth scope. So this, uh, active Fet probe more than good enough for measuring the bandwidth that we got here. So I'll use this, uh, long lead here for my ground. I'll put on the ground pin of the connector there because that's just, uh, very convenient for those who care about such things.

You can actually see what. Uh, point? I'm probing. Where is it? I think it's there. Geez, I can barely see that.

This is where you know magnification comes in. Okay, I'm probing a point there. I don't know what it is. I don't care.

There, it is. There's our signal. It's made up of a whole bunch of uh, stuff. but basically you can see.

Look, it's got some undershoot here. It's got a little bit of ring in there. It's got a little bit of ring in there. I'm gonna hazard a guess that that's gonna be due to our, uh, long ground lead there, right? So that is our thing.

but we've got actually higher frequency stuff in here. Look at this. Oh, I just happened to capture one there. Look at this.

It goes down up. We're at, uh, what? 10 nanoseconds per division? We're almost as fast as we can get here with this scope. But this actually does have some really fast, uh, pulses in here. So something? you know, Something? Swell.

You know the bus is switching. it's doing whatever. I don't know what point we're probing. Check that out.

All right. there you go, because that looks very sinusoidal we're talking about. that's our sign. exon x interpolation there.

So this is like, sort of. once you see that, you know. Okay, we're beyond the bandwidth of our scope here. These signals are just too fast.

But anyway, let's just go back to here. Okay, so we'll just try and capture that. Sort of like the most frequent one there. there.

It is. Got it. Okay, so I'll store that right? So what I'm going to do now is I'm going to actually, uh, change the ground into this. Instead of having this longer lead, I'm going to go for one of the shorter little adapter ground adapter pins we've got in there and it looks like there's a little bypass cap.

I've determined that this right hand side is the ground, so that's very convenient. and because that's right next to the point that I want to test Otherwise, as I showed before, like, you might have to, uh, like install one of those copper pads or something. You might have to like scrape away some of the ground here or something like that, and maybe put the copper tape over the top of the chip or something like that. Or you'd have to scrape away some other ground point somewhere.

or you know, solder in a little, uh, contact loop pin or something like that. So here it is. I've got my little adapter careful because you can stab yourself with these little bastards. There we go.

So we have this little 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. So let's try that 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, pan up, pan up. Okay, let's have a look.

I've changed my uh digitizer. definitely getting five gig samples uh per second and I saved my reference waveform. So let's single shot capture that, see if we can get it. No there we go.

Got it Now I can actually uh, adjust that waveform there to show you. There you go. So the orange one I've got there is the reference uh, waveform and this new yellow one is the one that we just probed and there you go. It is like it's of course like the same wave shape you can see.

It's got the uh, longer ground lead one, the orange one has some extra undershoot there and comes back and takes more time to come back up like that. and the one up here got some extra wiggle wiggle wiggle yeah on the top there some overshoot and so you know there are differences in probing right there. but at the moment this is the loading of the line with a one picofarad one puff active Pro which costs a couple of thousand dollars. Okay, now I'm going to use my 500 megahertz, uh, passive probe.

Here, it's the N2843. It's 11 picofarads. Okay, and yes, I've compensated this. Um, you compensate it with your probe compensation on the front, so everything's hunky dory.

I'm using my low inductance, high frequency, uh, ground probe attachment, so that's equivalent, uh, to what we had before. So um, we should get, um, because we've only got a 500 bandwidth scope here, then the bandwidth of the probe isn't really going to matter that much. Hold my tongue at the right angle and probe this. I think I got it.

But here's the interesting thing. I've changed the reference waveform to my uh, low inductance uh, short ground one before, so the orange one is the best we could get with our active Uh probe. So the exact same ground point, basically the same ground length and you can see that Well, you know our wave shape's the same. But look, look at this.

Um, it's a much higher level down here. Okay, this is our 200 millivolts are per division. so it's like you know, 50 odd millivolts higher there. and it's actually lower down here.

our yellow waveform there. So yeah, although we can see like the wave shape and everything up here, it's like when the bus is loaded differently because that's what this little, uh, you know, ramp up here is going here. I don't know the architecture of the Raspberry Pi, it doesn't matter, but I know there's something happening there with there and down here. we're actually seeing a larger drop across the Uh bus here.

which is interesting, isn't it? I it you know there's significant differences here. This, it wasn't the exact example I wanted to show. I just like it's a random example, but you can see the difference here between a 500 meg passive probe and and effectively A because of the bandwidth of the oscilloscope, a 500 meg active probe. They load down the circuit differently and I know you want to see it.

Okay, let's compare Dave's dodgy, um, homemade, uh resistive probe here with a 1k resistor in the tip. We'll give that a burl. 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. Now what we've got here. The orange waveform, of course, is our reference active fit. Uh.

waveform? That's a two and a half thousand dollar active uh. fat probe. Yes, it is uh, compensated. Uh? because you do still have to compensate them and it stores it uh, internally because it knows the serial number of the probe, etc.

And the yellow one is Dave's uh, do-it-yourself coupler buck resistive probe. Look at this. What's going on here? Well, it's obvious, um, that what's happening at this point Right here is that the bus is actually, uh, going open or something. I don't know the exact architecture of what's you know, the pin.

I'm actually uh, probing. It doesn't matter, right? It's like it's going open. And because the probe is one meg Dc resistance? Look at that. Um, it's basically it's not going to discharge.

Maybe if we got like a longer time period, it would eventually, uh, do a similar, like eventually discharge or whatever. But you see that the bus has actively changed. But because we're now loading this bus down with a 1k resistor or a 1.05 k resistor because we've got the 50 ohm terminator as well. It boom.

This is an R. This looks like for all the world. and it is an Rc discharge curve. So there you go.

What's that? You know? 10 nanoseconds per division? other? you could work that out. whatever for those playing along at home. But you can see how the, uh, resistive probe. um, actually it completely changes the circuit that you're actually measuring.

So uh, sure. like the 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 this is not some controlled experiment. This is just something I've you know, slapped together willy-nilly And 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? uh, actually. look. it overshoots again when 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 itself. Resisting 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 remember, um, it's a divide by 21 probe as opposed to the Active Fit probe which is divided by 10.. So if we Actually, uh, set up our cursors here and uh, 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 1.1 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. So for just that, we're talking about Uh 60 millivolts there. So it's actually precisely six divisions there.

and we were on Uh 200 millivolts per division. So that's precisely 1.2 volts. So the resistive probe is actually measuring 50 millivolts less. and that could be the load.

The extra loading of the 1k uh load. Once you, you'd have to check out the uh, driving strength of the driver actually used in this, which is the whatever our micros used on the raspberry Pi or whatever. But because as I said, we can't actually put in a a actual uh ratio, it doesn't let us put in our own user-defined value. it only does you know these fixed ones.

but if it did do that, um, then we could actually get you know. Well, we've measured it. We We can see that it's basically 50 millivolts under, so that could be like an extra 50 millivolts uh, drop caused by the loading of the probe. That sort of seems to be the case, but once again, this isn't exactly a really proper setup controlled experiment.

but that's possible. And it's kind of like, you know, the sort of uh, value that I'd expect, but you can definitely see the loading there. And by the way, no, this is not just a, uh, like a freak, uh, capture where? No, you know the bus did something different than before. This happens every single time, no matter how many times I capture this.

Um, the 1k probe is definitely totally different to the uh, active Fet probe here and you can see, obviously the bus was floating there and then it went boom. No, I'm gonna go actively low. Next up, Quite a common Uh requirement in electronics is to look at current waveforms, not just measure it with your multimeter, but you know, really see the waveform what it's like. And this is where a current probe comes in.

In particular, one of these clamp current probes which have a hall effect sensor and a core which just, uh, clamps through it so you put your wire through there and you can measure your current simply and easily. Because of course, if you try and use your regular oscilloscope probe. okay, how do you measure the current? Well, you can put a current shunt into your circuit of course. or you could design in a current shunt into your circuit that's a relatively common, but then, of course you've got the grounding issues.

Sure, you can use a differential probe, but differential probes are like designed for like high voltages. They're not designed for low voltages across current shunts so you know, pretty useless there. So you need like a super expensive multi thousand dollar differential. High bandwidth? Uh, like low voltage high bandwidth probe to actually do it? Well, bugger that.

Um, yeah. Eight current. This is where the current probe comes in. You can just put a loop of wire through.

It's not always convenient. Uh, of course, because well, if you want to measure current in a circuit, I'll show you another solution. uh for that up next. But if you've got like a wire available, then a current clamp like this is absolutely fantastic.

So there are a couple of uh, downsides. and I you've got to have like a wire accessible to uh, put your clamp probe through like this. B is that they're usually only designed for higher currents. um like in this mixig one here.

the Cp2100b which I see sell on the Eev blog store. by the way, it's awesome value for money. Um, it has like only a 10 amp and 100 amp range and you can't really get a huge amount better than that unless you go like really exotic expensive. So they're not for low current measurements.

So let's say you wanted to measure the mains current consumption of a complex uh product like this that either you own or you're developing or whatever. Well, that's actually quite difficult and you know you've got to get into the power supply and you've got to somehow like maybe get a loop through there or you've got to lay, install a current shut and use some isolated dead or high voltage amplifier and it gets a bit, you know, hairs on the back, your next start day going up, but in this case it's easy. There's our mains input cable for this, there's our brown active wire and we simply clamp around that. Bingo! That is our current waveform for this oscilloscope as you can see.

Uh, pretty poor power factor of course, you know, not terrific. And the good thing is most oscilloscopes will have support for current probes. So if I call up by the Channel One menu here and we just go into probe like this and I units, um, you know any good scope these days will have Volts and amps. so that's why I was able to have 200 milliamps.

If you're paying attention, you would notice that 200 milliamps per division. So this has support for current probes. And of course you can set. Just like the ratio of your voltage probe, you can set the ratio of your current probe and of course you set that to match the value on the front here.

Once you've done that, Bingo, it's calibrated. Bob's your uncle, You can measure, that's our mains waveform for this scope. Brilliant. try and get that that simply any other way.

It's just uh, no. So you can now get these for like a couple hundred bucks with like two megahertz bandwidth isn't too shabby. Okay, the lower cost version of this does. like uh, 700 kilohertz or something.

So unless you go for some exotic, uh, expensive, like you know, Tektronix one manufactured by gray bearded nude virgins that might have you know 50 or 100 megahertz bandwidth or something like that, then you know they are fairly bandwidth limited, but good enough for most, uh, switch and smitch switch mode power supply stuff. So yeah, current clamp probes. highly recommend you get one, they're great. Next up, we've got our most unusual probe on this list, and it's the positional current probe.

It's unusual because, well, as far as I know, please correct me in the comments. but only one manufacturer in the world makes this and it's the Aim Tti Iprober 520. And if you've been watching, I did this review back in this back in 2012. So yeah, it's been around for a while, but still nobody else has done anything.

Now you remember before when I said with those clamp current probes, you've got to have a wire available. You either got to have like a wire as part of a harness, or you've got to break into your Pcb and actually wire in a big loop of wire so that you can get the big current probe head over it and things like that. Well, what if you don't want to do that or you can't do that for whatever reason? Well, this is where the positional current probe comes in. With this, it has a magnetic sensing head on here that is as per its name, a positional current probe.

All you've got to do is put your probe over a trace on your Pcb and it can measure the current flowing through it. And I've done a whole review of this and I'll link it in. but basically it's got a calibrator in there. I'm not sure if you can see that there's a little trace in there.

Okay, there's a little Pcb trace. Okay, at the moment. it's basically, uh, zero like this. If I put it in there, I've got it to generate an Ac.

Uh, Karen, I can't remember how much you know. I don't know. 50 milliamps or something. Throw it flowing through it if I put that there.

Bingo. Look at that. This current flowing through that trace an Ac current. and if I turn it, if I rotate it like this, this is why it's called a positional current probe because it depends on the rotational position of the head.

If I put it in this axis to the trace, we're trying to measure, It measures basically nothing, but you rotate it like that and you get the full cur. Yeah, you can measure the current flowing through the trace. It's brilliant. There's nothing else on the market like it.

So if you need something like this, you need it. Now it's bandwidth. It's actually not too bad. It's better than the current probe we saw before.

it's actually 5 megahertz, but it has. You can actually set the bandwidth down to 500k or even 2 hertz down here. and you can adjust the trace position up and down on your scope and also the sensitivity. And it's got three different modes.

One is uh, wire comes with this ferrite clamp you put on there and it works just like a current probe, so that actually contains the magnetic field in there. and you're in wire mode so that makes it act like just exactly like a current clamp probe and I'll do exactly the same thing I did before is that measuring the oscilloscope waveform and bingo there it is. It's exactly the same waveform and you can calibrate. Uh, the thing.

The only disadvantage is it is a bit more uh, like dependent upon where the wire is in there. so if I move it like that, you can see the amplitude does change a bit so it's not quite as accurate as a proper uh current clamp probe, but you know it does a reasonably good job. And the next mode is the Pcb trace mode that we actually saw, so you know when the current flows through the trace there. And here's where you have to adjust the sensitivity.

And yeah, it's a little bit how you're doing. It's not like it allows you to see the waveform, but actually getting it calibrated, that's much trickier. But the value in this is actually being able to see the actual waveform. You don't necessarily say with most current probes, you just want to see the waveform.

you don't really care too much about the absolute accuracy of it. And the final mode is uh, magnetic fields. and you can measure those directly in micro Tesla. So if we go to the manual here, we can, uh, just have a quick squeeze at it.

Uh yeah. as I said, like a Dc to five megahertz. Uh, like the noise equivalent in a uh toroid? six milliamps, Rms. so it's not for you know, really low current measurements just like most, uh, magnetic current probes and then magnetic field measurement.

Uh, scaling. You know, 250 micro teslas, 200 amps per meter per volt output, and uh, in wire mode. Um, plus minus 10 milliamps to plus minus 10 amps. And of course, um, it's basically isolated so you can actually stick this thing right into the guts of a switch mode.

Uh, power supply. You know it does have like bare wire voltages and cat ratings and stuff like that, but you know, like look at it right. You can do your hands all the way back here. stick this right right up the clacker on the inside.

You know, down through the transformers and all the filter caps and all the heatsinks and live heatsinks and everything else. Stick them inside your power supply and uh, you're safe as and you can see here that you know for like, Pcb sensitivity. it's not completely linear like, but yeah, good enough for Australia. At least you get to see the waveform.

Now I couldn't be asked to set up another, uh, like experiment just to demo this. I've done a demo of uh where you can actually use this to trace higher frequency signals through a Pcb power plane. you need lots of other cool stuff like that. So I'll just, um, steal the video in the segment from my previous video here.

it is now linkedin down below. Hi, it's product review time. now. What I'm going to do is try and attempt to trace out a real ground current on a Pcb like this.

And as you can see, there's a split Pcb plane in there. So I've got my current going in over here coming out over here and it's got to go through that tiny little trace down in there. That's the only way that it gets from there through to there. There's the split ground plane there, so we shouldn't get any current flow around in here.

We shouldn't get any current flow in the ground, fill down in there. We shouldn't get any current flow down in here. We should just get the current flowing through there through that tiny little trace there if you can see it and down around through to here. Now I'm using a one Kilohertz signal here, but it would work for uh, Dc as well.

But just remember, you've got the earth's uh, magnetic field as well. So when you move this thing around, you know where you you're going to get an offset. uh, shift like that. So just be careful.

But here we go. there's our reference waveform and we don't have to worry about the calibration on this pot at all because we don't care about the magnitude. We're just tracing currents here on this board part of the ground plane and you'll see we've got absolutely nothing there at all. We can change the orientation and we get that offset, but there's no one Kilohertz signal is nothing flowing through that part, the ground plane.

But here there most certainly is. Once again, if we get the wrong orientation, it's going to vanish like that if we hold it vertical. But if we keep the correct orientation according to the magnetic field of how it should flow, then bingo. We still get the waveforms.

see the currents going both sides of that hole there here like this, and once again, it does. Some of it does flow down around there like that, but the majority of it's going to flow through this top part here and it's going to flow up here and you'll notice that it won't flow down into that little fill that little void down in there. There is no current flow there at all, so you can see the current flowing through here. And likewise, there's going to be nothing flowing down here.

They're electrically shorted together, but there's no current flow. This is a great visualization learning tool as well as a real practical tool for determining where your currents are flowing in your ground planes. and there it is flowing down there. and it's Look, It's not going down this little bit down here.

Very little down there at all. Tiny little bit flowing through those two pads there. But as you can see, it's all going to flow through that trace there. That one tiny little trace which connects the two split ground planes.

and it's going to flow up here and all the way over to there and look down here. There's nothing in this little void down here. Zero that out. There's no current flow through any of this stuff down here, because that's where it flows through that bottleneck there around here and down into there.

So yes, this thing, uh, isn't cheap, but it's unique and there's nothing like it. so I'd recommend this if you're doing like lots of Maine's big switch mode power supply design and stuff like this. Just being able to get in there and see waveforms just without around. it's worth its weight in gold.

And the last probe we've got the Emc probe. Of course I've done like what half a dozen videos on using Emc probes. So like yeah, I've already spent enough time on this video. I won't go through it again.

I've even done a video on how to make your own one for like what was it? 10 bucks or something? Um like that. So 10, 15 or 20 bucks? Um yeah. you can make your own. Uh, of course you get magnetic ones like this which I actually have the Uh loop and you get them in different loop sizes and this one here actually has a loop in there.

So these are called H Field or Magnetic Field probes and then this one here is called an E Field or Electric Field probe and well I've done very interesting videos and differences between magnetic and I've demonstrated in the magnetic Uh and electric fields and things like that. but great for doing uh, Emc electromagnetic conformity uh, pre-compliance for your Uh products and generally are the output levels of these are very low. so you use a wideband Rf Uh signal amplifier. In this case this goes up to a three gig from Uh Tech Box.

And but you can, as I said like you can just make your own out of a bit of coax is basically just a bit of coax in there and that's it. Um, and you can buy these amplifiers for like 10 bucks on Ebay? Uh well, not this one, but like a little bear board one. Um, and Bob's your uncle, You've got yourself a Emc pre-compliance very handy for like tracing down Emc faults and things like that. Once again, I'm not going to set up experiments again just to demo this.

I'll link in my Emc uh videos, but that is another different type of probe. Highly recommended. You should have one just because like just make one yourself. I mean this set costs you know, a couple of hundred bucks and it comes with like the calibration charts and everything else and uh, which is fine but these do-it-yourself ones Once again, for 10 20 bucks just like uh, your Here it is just like your uh, transmission line resistive probe down here.

I'd like why not just have a couple of these made up for when you need them. So there you go. I hope you enjoyed this. uh, little two-part series on looking at all of the different types of Uh probes available for oscilloscopes.

There might be other obscure ones out there. Please leave it in the comments down below. If you think I've forgotten something, uh, important or something exotic like this, you know, iprober, uh thing. other.

I'm sure there are other exotic oscilloscope probes out there, but I think I've pretty much, uh, covered. You know, all of the general ones that you're going to find or have potential use for in the future. So yeah, you've got your times 1 x 10 switchable probe with your scope, but there's a lot more out there that allows you to do all different types of measurements under lots of different scenarios that you might encounter in electronics. so I hope you liked that.

And if you found it useful, please give it a big a thumbs up. And as always, discuss down below in the comments over on the Eev blog forum. each video has its own forum link uh, Linkedin and down below where everyone discusses this stuff. And of course you can check me out on the other platforms where I occasionally, uh, release exclusive material not on Youtube.

Catch you next time you.