GeoSci.xyz EOSC 350 (2017), 9 Nov 2016

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From YouTube: EOSC 350 EM Lecture 1

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Lecture on applied electromagnetic geophysics.

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On a Friday afternoon after the exam yeah, so we got me back so yeah. The exam is long goes too long. On the other hand, there was a lot of benefits to having an exam. That was that long, because, first of all, it actually gave you practice on each of the three sections. So it's the short answer is really that you know that people spent the most time that, but that gave you you know at least one example for each of those sections, which is that we can really did you put.

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The second is yeah use, multiple choice, questions really, don't tell us very much.

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You know we're looking at the distribution, the correlations between the multiple choice and the short answers, and it's there's really not a very good correlation if you have to make an evaluation of who's the top students, just by looking at the multiple choice, the chances are that you could. You could be pretty wrong and if you think about it for a multiple-choice question, we've got four answers.

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Usually two of them you could throw away. That means that you're really stuck between two and even if you knew nothing, then that's a 50/50 Jackson, so I'm not overly enamored.

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They do provide some information and the office will provide that opportunity to to study. So we won't take that exam today, we're going to take it up when we get a little bit of breathing time, but you've got the lab this afternoon. So there's a few basic things that we really need to get.

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So that's the that's our goal for today. So if you remember where we were at the end of last lecture, we were looking at.

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We're kind of looking at electromagnetic induction and the example that we were using was this guy that was coming to in the security system and our the general sort of physical idea of what's going on is that we've got a transmitter here, so that's giving out a time-varying magnetic field. If that sees something that's conductive in here it generates currents and if those those currents then generate another magnetic field, that's picked up by the sensor. So those are the three elements that we have and we encapsulated it.

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So here's the five guys here that are really important and we're going to go through we're going to go through them today, one by one and make sure you've got all of the basic concepts.

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So the first is that we've got some kind of a transmitter and usually that's just a loop of wire and that wire generates a magnetic field. So if you remember that right-hand rule, if we think about a current, that's going in this wire, then that magnetic field is going to go like this and is actually going to look like a dipole. So, if we're sitting anyplace in here- and we see this time varying magnetic field, then that generates this electric field. So that's that force that is going to cause electrons to move.

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If their material is conductive, then that gives us an electric current density J, which is equal to Sigma times, either cut the conductivity, and then those currents produce a secondary magnetic field that we can measure and receive. So that's that that's the process and we're just kind of gonna step through I fit you're, really all rested up from the weekend. You have the opportunity. This is probably know one of the most kind of interesting and challenging mental exercises.

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You have in this lecture today, just to kind of keep track of of everything, so we're gonna take each one of them separately. First of all, we're going to have a transmitter and the primary fuel never going to look at something called the magnetic flux and something called coupling. So those those are essential elements that we're going to need, then we'll look at the target. What the induced currents are secondary feels what the receiver are and the data so we're going to take each of these in turn.

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So let's look at a generic system, so we've got a transmitter so, as I said, there's just going to be a loop of wire and we're going to attach a generator to it, and it's going to give a primary field that will propagate into the earth. It could also propagate to a receiver. So this primary field goes everywhere. We're going to have something in here. That's our target.

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That's going to be inside the earther for what we do, we're just going to put it in free space to start with I'm, never going to have a receiver, which is just another coil of wire that will be merged. So those are the three elements: transmitter target and receiver.

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So this is something that we should kind of. Remember we're talking about the Earth's Earth's magnetic field and how are we thinking, but the Earth's magnetic field being generated? Nobody.

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Yeah, so we've got these currents inside the inside you're inside the core, so those currents then give rise to our magnetic field, and if you want to think in the earth you can just think about soda inside the core and there's just some great big current that that's going around and then the magnetic field at any point, is just given by that rule. So if you think about putting your fingers your thumb on this current here, you can see how it would sort of curve around, and so you get a magnetic field.

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That looks looks like that, but because it sort of you know at each point here, it's kind of going around by the time you do it all the way around. It actually looks something like that and that's a field that you recognize as being like that of a dipole.

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So one of the first things is that if we have a loop of current, so the current I that's going in here, then the magnetic field looks like this, which was just like a dipole.

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We can also calculate what the strength of that dipole is remember. We had this thing called the magnetic moment when we translate that to a loop and the current, it's the it's just the area of the loop Thanks, whatever the current is so if we have some particular area here, then the strength of that that current multiplied by the area gives rise to that magnetic moment. So that's actually how we make that correspondence between you and the currents and both the magnetic field and the total strength.

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So good so now, I've got a magnetic field that looks like this, but I've got a generator, that's attached to this and that generator might be putting out a you know a sinusoidal wave.

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So what that means is that at some times the current is going this way in the loop and that stops, and then it goes this way. So it's alternating pointing this way this way, so you can imagine what that happens to be the magnetic field.

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So if the loop, if the currents flowing this way, then the magnetic field is pointing this way of Chris. The other way is pointing that way. So what point currently this way, then that way, this way that way, some things that you there's a time varying magnetic field. So that's the ticket. We have a generator here. That's got an oscillating current. It generates a time varying magnetic field so that now, if you're a target body there, then you're going to see this time varying magnetic field. That's going to generate currency, okay, so the.

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Time varying current gives a time varying magnetic field. You can also see the other thing that happens too. Is that, depending upon the orientation of this, we can imagine this guy's like current, is going in here, so I got a dipole, but if I put, if I move it this way, then I've got no particular orientation of the dipole I move this way up. Another orientation so, depending upon the orientation of my loop I'm, actually going to get different magnetic fields wherever I point.

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So the next thing that we we need to do is to quantify something called the magnetic flux.

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So I've got a loop suppose I go. Can you guys see that so I've got a loop? It's sort of sitting up here. I've got a primary field that that's coming through there. So there's always going to be some magnetic flux. That's coming in Rizzo occur to some magnetic field.

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We can define something called the magnetic flux which is equal to B at magnetic field, dot and hat da, where the area where the integral is over the area of this of this loop, the dot hat, means that it's just just a normal component of U. So if I've got something, then if I've got a magnetic heel, it's coming in like this and is it is constant. Then the flux is just going to strengthen that magnetic field times the area.

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But if I move this like that, then I get much less flocks that's coming through and if I move it like this, that I don't have anything, that's really penetrating that particularly loop. So that means that the flux is equal to zero. So we're trying to show this in this next diagram here.

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So if I've got and I can feel, that's come like this and I've got a coil that looks like this, then that normal component of the flux is just one that's straight through, and so the total flux is just equal to the area times whatever HS. But if I orient this a little bit, then I've got a smaller amount flux and if I make it like this, then I've got no flux, that's coming in through there at all.

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Okay, so we've got a loop. That's it's a transmitter. It's providing a magnetic flux that goes through here, and the value of that flux depends upon that orientation of this transmitter, and this guy here just to see how okay one more thing is that we cared about the time variation of that flux. So we don't just care about this guy.

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We care about how much it's changing in time, because the magnetic field that's impending on it, doesn't do anything but did I change that then it's going to cause some currents to flow, and the thing that is is important. Is that time rate of change of flux you circle is called a voltage and that's just equal to the this one here: minus D, Phi, B DT and this minus sign here. Anybody remember why we where'd that came from last time.

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We talked about a guy with particular.

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Right exactly so, that's what it's happening. There was actually a name of a law for that. It's a guys named Lance, so Lance of this law, I've told you how and that that's the thing that tells you how that current, you know which way that current is gonna, go.

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Okay, just to recap slightly so we've got a coil of wire, gives a magnetic field. Just like a dipole then, depending upon where your target is and how the target is coupled with these fields, then you get places that the target is not coupled, so the magnetic field is kind of going. You know parallel to the plane of so here the magnetic field is coming down here. There's nothing! There's nothing!

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That's cutting it, whereas if you're sitting up here, then you've got the full force that that's coming so now, you've got really a highly coupled system, so wait you're sitting in these locations here, you're actually going to have a lot of a lot of currents that are going to be generated because you're going to be really well couple.

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So these time varying fields are on here are going to give rise to currents that that are going to go in this body. And now what we want to do is to take a little bit of look at those currents and then see what the magnetic fields are that are going to be generated at the receiver.

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So that receiver is just you can just think about it as another coil. That's that's sitting up there and.

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Transmitter gives rise to this feel that comes out here. Part of it goes onto the body, but there could actually be something that is measured here at the receiver, in what we're going to do. We're going to subtract this primary field at the receiver, so we're only going to be looking at what the secondary field is. That's the field for here at the receiver and the quantity that we're going to be interested in is how much the secondary field is to this target compared to what the primary field.

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Yes, so we're going to be looking at a datum that looks like this, so our instruments could measure the secondary field divided by whatever the primary is.

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So now what we want to do is we're going to take this in two parts: we're going to first of all kind of sketch what the nature of the fields are going to be, and the thing that I'd, like you to try to keep in mind is the idea that we're going to have a system whether we're going to use is something called an EF 31 and it's basically it's basically a rod and it's got a transmitting coil on one side and it's got a receiving coil on the other, and you could take this guy and you just got to walk along with it, and if it happens that there's a you know a pipe or a plate or something here, you're going to get a particular characteristic signature, and that characteristic signature is what looks like this.

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So here's, our PI and the signatures you walk along like this is going to be something. Then that looks like this. So what we're looking at here is our data. That's that HS HP and it's going to have some signature, looks like this and it's going to be sort of a maximum right over over the pipe.

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So what I want to try to explain today is why we get this kind of signature and the reason I do. That is, if, if you can understand at the end of this lecture, why would we take this particular instrument over a pipe abroad or something like that as we get out something like this, and you really will have understood all of the essential ingredients with respect to electromagnetic induction or it needs a lot.

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So that's our game plan, so there's going to be a few things. You got pay real, close attention to what's going on, I'm, not sure which blackboard is the best to write on in this case.

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Can you guys see that one at all.

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So what we're going to do is to look at a case like this. We've got a buried pipe and we're going to have a system like this eeehm 31 that I just talked about, and it's going to go over top of here we're going to try to sketch out yields and we're going to end up with something that looks like this.

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It's going to have a positive in one side, it's going to have a big negative over here with a maximum being application of light and then another positive, so we're going to try to figure out how that sketch works and why it's being plotted as it is so, first of all, we've got our transmitter and that transmitter so that exclosures of currents, that's gonna flow in that direction and that's going to give rise to a primary magnetic field right.

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So if it's like- yes, okay, then, if your current is going this way, then we get a primary field.

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That looks like this right, so it's that magnetic field that we that we have talking about if we now put on a target in here, so let's not make it another. One here so here's our transmitter and here's our target, so it's a plate or some plates a little bit easier to these look. So imagine, we've got a vertical plate and now we've got a magnetic eel. That's coming in like this it. So here's our primary field and you notice that this primary field is coming into the plate.

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Okay, so if the primaries field is coming into the play, then which way is the current going to flow into place? So now you imagine, you can imagine the plates like this primary fields coming in like this, and so there's gonna be a current. That's going to be set up in this place. I'm gonna go this way or it's going to go this way so which way is the curtain.

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So we've got to we've got to impose this, so here is the current going to go in or out.

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It's going to come out, so sorry current is going to be coming out here and in like, and so now when I do that got my right now rule so now my secondary field is coming out like so by just drew the secondary feel.

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Yeah, my secondary field is kind of coming out like that yeah.

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That's Lenz's law, oh right, so if I, if I think about it, magnetic feel this that's coming in and sitting we're assuming it's increasing, then I've got to have a current. That makes it then going to feel the close itself. So remember remember when we did the little magnet in the coil and we shove it up the magnet damn. Well, we shoved it in. It will be one way to shut it up or pull it up the other way.

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So all of that tells you, okay, which way is it's going in and nature for some reason loves to not have these things change. So if you change Megan feel it's going to work in opposition, so that's it for understanding which way this guy goes.

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Okay, so here's now the secondary feel that looks like looks like this okay. So as long as my transmitter, so suppose my transmitters sitting to this side of the plate, if I now look to see which way. Oh so my data is H s over H P and if you notice I'm, plotting it as positive and negative. So there's a question: okay, what determines? Let's? My sign convention about positives and negatives, my sign conventions good to go if HS is in the same direction as HP.

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Then I'm going to say it's positive.

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Okay, that's that's my convention. I get to choose so now. Let's look at the situation that that I've just drawn. If I've got a transmitter over here, then my primary field is coming down. Okay, so my primary field is like this. So now, let's suppose, I've got a receiver. That's sitting up over here primary fields down and now my plate. Look at my plate, I'm sitting over here. My magnetic field is the secondary field is also coming down.

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So my secondary field from the plate is also coming down, so my primary field, secondary field, are going to be in the same direction on this side, and that means that if I strike to just sketch things out that, if I'm sitting over here with both transmitter and receiver on one side of the plate, I've got that smaller scale that I'm going to be sitting here with some kind of a positive number okay, so that accounts for this part over here.

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Okay, so far, so good, okay, now, what's going to happen, I'm gonna, walk and then there's going to be a place where my receiver coil is actually going to be sitting right above the plate.

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So why would we care about that.

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Suppose so, I've still got I still got my transmitter over here.

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Suppose. If my receiver was sitting right here, then what would the value of of the day can be can be zero correct and why.

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The primary fields couple.

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Secondary field right, so this is field here right from here. It's like this, so if you know, if that's my receiver coil, then my magnetic field lines are like this, so I've got no flux.

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That means there's got to be a zero crossing at some particular location in which and that's the location at which the receiver is sitting right up over to over top here. So that gives us this point here now. What happens when the transmitter is over on this side, but my receiver is over here.

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Well, when the receiver is over over here on this side, then my secondary magnetic field is up.

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My primary field was down so they're gonna be opposite direction, so that means that this is now going to be a large negative value.

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Okay, as I keep coming over I'm going to actually hit a spot in which my transmitter is sitting right above the above the plate.

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One's going to be the value of the datum when my transmitters right above the plate go to zero correct and why.

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You're halfway there, that's right after why is gonna, be zero right.

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So now it's a different kind of kettle of fish.

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I've got a I've got a plate here and I got a transmitter. That's got a magnetic field. That's going like this! There's no EMF! That's producing here! There's no! There's no flux! That's going through there! So I don't have any any signal. So there's no currents.

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That gives rise to another zero and then later on, when they're, both on the same side of the plate. It looks like this.

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So here is my final picture.

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There was a lot of stuff that went into here, so it's going to take you you're gonna have to sort of sort through this a couple of times before use before you really kind of crystallize it, but the ideas kind of recap.

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So here's actually the e/m 31 I- will bring one in if you can take a look at it. The the transmitting coil it's about 10,000 Hertz, and this is the same one- that we used on the expo site. I showed you those data right at the at the beginning of this and you'll see them later on, because we're going to go over and see if we can't find that contaminated oil spill and some wires and stuff like this. So here's here's the thing it's about 3 and 1/2 meters.

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Long when both the the transmitter and the receiver are on one side, then the secondary we get current. When the transmitters on this side, we get currents that are going in one direction in this in this plate and when the receivers here then the primary and the secondary field are in the same direction as the instrument gets over top so that the receiver is sitting right over here, then we have a zero, a.

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Little bit later, when I got the receiver on once your transmitter and one receiver on the other, then I get a very large signal that these are in opposite direction. So I'm going to have a big negative, so now I'm sitting right here.

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And then I come across now I got another zero crossings, but it's very an entirely different physical basis. This guy is it's got a zero because there's no currents that are being developed in here so I got two zero crossings. First, the first one, because it's null couple there's actually signal there. But if my coil is not orange in the right direction to see anything, and this one is zero, because there's just no currents being generated.

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So that's the sketch of the signal and as we go through and we over the next sort of week or so you're going to become more familiar with kind of what's going on physically here and you can expect probably on the final exam I'll ask you some kind. You know scenario that somehow related to this. So it's going to be gonna, be thinking about transmitter which way the primary fields are going, which way the cars are going, which way secondary.

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Because the the thing about this is not so much understanding like okay, a tight curve should look like this, because, if I change the instrument moves that they won't look like this. But the point is: if you can actually talk your way through this, and you see that it's a lot of stuff, that's going on physically, you can actually talk your way through this and come up with right shape. Then you know you understand it.

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So it's the same kind of thing that we had when we did the magnetics right, so that if you could bury something at different parts of the earth and decide you're going to do this component or that component like you're good to go, you understand what's going on and that's the point.

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Okay, so we've got the basic element down here: we've got fluxes, genomic trees.

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Remember what I first showed you the data from the expo side, I showed you two images and I said well, one was the real part and the other was the imaginary part. What.

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Now my understanding is that if I wrote, AI is equal to the square root of -1. How many people would know what that is.

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And if I wrote e to the I, only good tea, how many people would know how to expand that? What is it.

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So when we deal with electromagnetic, so I can deal with a lot of systems mathematically.

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It turns out to be easier to couch the mathematics in terms of what's called complex numbers which involve the square root of minus 1 and 2 right things in this complex notation, so we're not going to go there, but the reason that things come up like this is that if we take something like this- and we write this in terms of in this form here- we often refer to this guy here as being the real part and then because, there's an eye in here, we call this the imaginary part.

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So this is kind of two to two parts that are going on, so the data are complex, but the understanding of the data is actually not so difficult, because what that complex thought is this kind of turn things into. What's called a phase lag, so let me yeah. Let me try to explain this so suppose. I got suppose. I got my boy, so I got a transmitter. That's going like this right, so it's oscillate there, everything in the field of that transmitter oscillates with that same frequency.

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So if this, if the frequency know is like ten thousand Hertz or a thousand Hertz.

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Then, oh and Omega 3 Omega is 2 pi yeah, so Omega s--, angular frequency, so 2 pi times. So this is in Hertz. This anger, 30. Okay. So if I've got a transmitter, that's operating at some particular frequency and there's something happens inside here. The current feels it did come back. It has to oscillate at the same frequency so when I'm in receiving something I'm measuring something that's happening at the same frequency and the only information I get I can get two pieces of information.

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Anybody suggest what they might be.

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For me, I can have an altitude, so if you you know, if you're there and being the source of some harmonic frequency, it could be an opportunity and the other thing it could be a phase.

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So here's my transmitter. It's got an aptitude that looks like this right, then I measure a voltage and that voltage is also sinusoidal.

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So it's got some amplitude, so that's important, but the other thing is that it's phase shifted so when this hits a maximum so that at the time that this hits a maximum, which is there this guy yo, it's not a maximum ez is shifted a little bit and that that phase shift here at the flip side denotes how much well do you notice how much these things are differ in in phase okay. So what I'm gonna measure?

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Okay, is some way it's got an amplitude and if I'm going to represent my time variation, it's going to have like a cosine, Omega, T, plus some kind of things all right. So the thing I'm going to measure is going to be looking like this, but this now you can. You have seen before and you can take this and you can break that into two parts right. So the cosine Omega T plus subside goes to cosine Omega, T coasts, upside minus, sine Omega, T, sine side, right, flipper,.

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So cosine Omega, T plus some constant, goes to you know a cosine Omega T, that's the first step and then a cosine side and then a minus the sine.

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So if there's some opportunity to fit here, you're not good, there we go, and here we have an aptitude. So let's, let's combine those things. So let's take this guy in this guy, so that gives us an a cosine Phi times. Cosine t minus a sign. That's I sign.

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So, what's this mean so my my primary wait is that traction is he's cosine over your key, so he's going like this right and now I've got something that's coming back and I can decompose it into two parts. Part of it is in phase I can never do this. Okay, so I got this aptitude here and I've got this down here he's coming, while he's he's in same phase that just has different allergy. Okay.

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So that's what this first part is. This is telling us for what something is coming back, how much? What portion of that that's coming back is in phase with the primer. Okay, this guy tells us how much is out of phase right. So, if he's coming down with this okay, so this that's these guys right.

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I'm gonna make it sound acute small right all right, you got it so there's there's a certain amount, that's in phase and then there's a certain amount. That's out of phase the interface part. We give different names to it. Sometimes we call it the real part. Sometimes we call it. The in phase part two names mean the same thing and you'll see these all the way through the literature. So this is this part here.

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This is sometimes called the real part and it's sometimes called the infant.

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This part is sometimes called the out of phase.

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Is sometimes called quadrature.

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And it's sometimes called the imaginary.

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Historically, those are used interchangeably and you just kind of get used to these. These are the three words all being exactly the same thing: there's two words at all being exactly.

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So now we could go back to our data, so we've got a primary field.

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So we got a primary field: that's H sub P for primary Kosova T right, so that tells us how that one's also and then we got a secondary field. That looks the same H s. So it's a different altitude, but it's got a cosine Omega T plus subside so different things. So if we carry this guy out- and we do that separation- we get something like this and then we're going to divide it by whatever the primary field was the 8hp and we get this guy here.

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So we've got this part. That's the in phase of the part, that's other things and in phase is then just given by this quantity and the other phase right.

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Okay, so we're actually making huge progress.

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Okay, so we've got the ball whole concept of inducing currents and getting these secondary fields back and now it's that ratio of the secondary to the primary that's going to be important, but because of how the waves come back, there's going to be a certain part. That's in phase and certain parts.

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The last thing, and then we can rest your minds- is to try to figure out what portion goes into this in phase and what portion goes into thee out of phase and how all of that kind of relates to those data and.

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The crux of this is that if you have a target and will work with it, what you're going to do in the lab is you're going to have a transmitter and you can have a target and then you're going to have it have a receiver. Yes, this target is just a loop, it's just a loop of wire and from circuit analysis. If that's these circles right, so we we got a battery and then one of the components that we can have in a circuit, a.

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Resistor good anything else, a capacitor anything else and if you could have an inductor okay, the inductor is l, resistances R, and actually we don't have to worry about the capacitor.

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So we're going to represent our circuit, our target in terms of kind of resistors and inductors.

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In the GPG there's a little bit of explanation about how we get there and I might go back and and talk a bit more, but for now I just want kind of get the the overall concept and get the picture because you're going to be seeing this picture this afternoon, so I want to get you. This fascia is equal to first of all, PI by 2 and then there's an another terming here, which is the arctangent of Omega L upon R Omega. So frequency L is the inductance and R is the resistance okay.

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So you can think about your target as being a circuit, and it's just got this L here and ended arm, and the thing about this is that when, if R gets to be really large, so let's suppose you got a really big resistor, so imagine in the ground. You know: there's just no conductor there whatsoever. Okay, the resistance just goes to infinity and R goes to infinity. What is what is this guys? Remember. Our cannon blotchy R goes to infinity. What is this argument in here? Zero Arcanum zero is.

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Zero okay, tangent function.

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Okay, so the tangent, so that gives you zero. So then this just goes to PI by 2. So if R goes to infinity, then upside the spaceship is just PI by 2. If.

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L gets to be really well acted if Omega, the frequency goes to 2 0, that's another way of making this funny equal to zero right, so we kind of made our very large or Omega, very small, and in both of those cases the art Ken goes to zero, and so everything goes to just pilot you, okay, if arm, however, happens to go to zero, then what happens in this guy infinity and if that goes to infinity, this guy is PI by 2 PI by 2, plus PI by 2 is equal to PI and yes, we've got.

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You know two to sort of M members.

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The in phase part and the out of phase part then get plotted up in the following manner because of this, because it progressively shifts- and there there's a picture that we'll be dealing with in which this axis here is the product effectively of Omega times Sigma or Omega, divided by our resistance. So as we get higher up into frequency, so this is this, is you can basically think like? This? Is a good conductor really high frequency good conductor go over here, and in that case the.

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The phase shift gets up to be five by two, and we end up with something called the inductive limit here, where everything is, it is in the real part and when we have very low frequencies or poor conductors. We end up the real part like this, and this outer phase part has this kind of the signature that's attached.

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So the details about exactly how this comes to being I think is not so important. It's just kind of getting a sense of what the response of that of that conductor is, and these two parts here, the imaginary, the out of phase part and the real part behaving something like this. So as you get to be, have really good conductors. Virtually all of the information is in that real part when you have intermediate conductors, there's information both in the out-of-phase part and in the real and when you have really poor conductors.

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Most of the information is in that out of things part. So how does this translate back into the flaw? So we've we've worked and we've got this iconic diagram here. So here's your bringing the e/m 31 over top of that pipe okay, we kind of figured out how to do that. It's just that now, we've got all we got one more detail to think about, and that is that actually, oh well, that's the shape when we change something. We've actually got two numbers of real and imaginary part.

A

How do we know which is which or what the other one looks like? So, let's suppose that this is the real part here.

A

If we look at this particular diagram and if we've got a really big conductor, it's a rope over here, then the real part is much bigger than the imaginary part, and hence a signal that we should see. If that's the real part, then the imaginary it'll have a same shape but it'll be really smaller amplitude.

A

So both things will have the same shape, but the amplitude of one versus the other depends upon whether you've got a big conductor or a small conductor. So, in the cases where you've got a really large conductor, as we'll see when we don't ever have pipes, then most of the information is actually going to be in the real part and the signature is going to look something. On the other hand, if we go to something that's got a much smaller conductivity, then these things could be reversed. The real part.

A

The real part look like this and the imaginary part.

A

Okay, so where are you gonna go this afternoon in the lab? You're gonna have an app and you're gonna, have a circuit model and you're going to cut the wave your way through the draw of that kind of characteristic curve, and then there's going to be a question about okay, if you've got a big conductor or small conductor, you know which of these guys so yeah you'll be able to basically review all of this stuff.

A

So that is good. You guys deserve a gold star that one's probably more stuff.