Advanced Signal Application: Connection, Clamp, Induction and Frequency Choice

0:00So hopefully, I've gone into a tiny little um thumbnail type image, which is probably a lot more easier on your eyes. As Pete said, we're covering the 8000, 8100, vLoc3. You guys might be using other kit out there. Whatever kit you're using, it's going to be very, very similar to this um

0:23And my laptop is going very, very slowly at the moment. So we're going to cover aspects of um things like how to apply signals, the best way of doing it, frequencies, aerials, CD, that kind of stuff. And as Pete said, if there's anything as we're going through you guys want to add in, you know, thoughts, comments.

0:47Um you're saying you're having playback problems, Stefan. I don't know about what Jeff's saying about being hard to log in today. I don't know if that's just web traffic or I'm no expert on this stuff. Well, there are issues this week with the login system. I'm still playing around with it with the notifications and um and logging in and stuff. I'll I'll sort that, don't worry. You You carry on.

1:13What we What we have to assume on these courses, guys, is that um you've used the kit quite um comprehensively, you've probably had training before. So we have to make some assumptions. Um obviously, once we start doing this um as a proper online platform, replacing some of the um traditional methods of training,

1:35we'll have a much better feel for, you know, everyone's experience, but So with any of this kit, and you'll notice quite predominantly there's some RD transmitters, but as I said to you a minute ago, a transmitter is pretty much the same as any other transmitter. Frequencies, power outputs, and things like that may vary, but the methodology is exactly the same. So

1:56with the TX-10 or a vLoc transmitter, whichever you guys are using, you've got generally four different ways of doing it. I suppose technically there's five, but for most people, you're probably familiar with the um the first or number one, two, and four.

2:17So number one's direct connection, obviously just taking your red and black leads, connecting it up to whatever you're trying to locate. Number two is signal clamp, which is very useful, common way of tracing things.

2:36Number three, you guys might not have come across it. Some of you guys might have done. Plug connector is useful in places like military sites, big industrial sites. Most of us aren't particularly um aren't particularly um overly happy with the plug connector because of some of its issues, but it can be useful at times. It just allows you to plug the transmitter into a plug socket in a building, switch both the transmitter and the plug socket on, and that will put a signal into the live LV supply. There are some issues with using those things, but they can be useful. And then induction's induction.

3:01Every transmitter is capable of producing an induction signal. Uh if we get time, we'll cover some stuff on induction and nulling out. We'll see how we get on. So I'm guessing you guys are familiar with how to use connection, connecting your red lead to what you're trying to find, black lead to an earth. It's always considered best practice,

3:22even though the transmitter produces an AC signal. The reason being is we're going to cover CD later, and that is very important that you do get those leads in that um orientation. Probably one of the biggest issues when you're out there is trying to get an earth, and this tried and trusted technique has been around for years. Uh it's never been very well documented.

3:49We've started doing some booklets which go along with the training course, which show you these little tips and tricks, but water's been or any kind of fluid has been a technique for getting earth, so where you can't get the earth pin in the ground. In this scenario here, we've clipped onto a steel gas riser, and we're getting an earth. Just any old water will do, or Coke, or tea, coffee.

4:13Just lay it down next to the brickwork so the water soaks away. The obvious thing to say on a wet, sorry, on a hot summer's day, you're going to need quite a lot of water. On a wet day like it is in Bristol today, [laughter] just find a puddle. That'll do.

4:33We're going to cover a bit more about this a bit later on, but earth placement is a very critical part of how your signal's going to be traveling. We were talking about doing another session, and this is day's probably three from my normal surveyor course, um or certainly just a part of it. On day two, we cover basic electrical theory, which is a very useful part of understanding how a locator and a transmitter works.

5:05But what we're doing there is creating a simple electrical circuit. The one thing that's missing, or should have been added onto this slide, is the arrows should always be double-headed. Because it's an AC signal, unless we're using current direction, we don't have any choice in which way that signal's going. So you've just got to remember that signals are going to be

5:29traveling on other adjacent pipelines. This is also a function of frequency as well. One of the questions we tend to ask, and Pete asks it on his um CAT and Genny courses that he runs, um where are you guys normally told to place the earth, or if you did training previously, where did they tell you to put the earth? Just uh if you can pop those comments up,

5:57just out of curiosity. And if you guys have done the Genny session with me, you'll know the answer to this, so no cheating. [laughter] I'm not seeing any responses, but that may be the delay, or maybe mine's not updating. You get any responses, Pete?

6:24I kind of put you guys to sleep already. [laughter] They'll come through shortly. The the because we've got so many on it, the delay's a little bit longer. When we're on this as a as a paid event, there won't be the delay on it because there'll be much smaller numbers, so just suffer bear with us on that. So Peter, you put 90 degrees and furthest away from the line we would like to trace.

6:48There we go. So we've got a random mixture there. Closest possible, 90 degrees far away, 90. You guys are putting 90. There is a logic to that, and it was something that was always trained um or it was a technique that we were told to train people on probably 20 years ago.

7:10It was a technique that we were told to train people on probably 20 years ago. And one of the main reasons for that is the transmitters back in those days had very poor impedance matching. So, you very often struggled to get any kind of signal out of your transmitter. So, by running your earth away, far away from where you connected on, you are creating more of a circuit.

7:37In modern transmitters, a lot more power, a lot more frequency options, and very good impedance matching. That's probably one of the things we get people to understand and do less and less of. What we try to do nowadays is encourage people to keep the earth as close as possible unless you're obviously going longer distances. The main reason for that now

7:56is the fact that you've in this scenario here created a much more localized signal source and return. So, in this case, you're going to get less on this one and a lot more on this one. Again, this is a function of frequency, but keeping your earth as close as possible. And what the black lead is connected to there is just the frame around, the metal frame around the, the lid of a valve box, if that was a pipe line. Steve, is it worth me just jumping in there with my slide for a second and doing that section on the Genny just briefly to show them? Yeah, if you want to. Do you want to just turn your screen share off? Okay, I can. I'll stick mine on.

8:43This is, um, a section I've been covering on the Genny a little bit, guys. I'll just run through it very, very, very quickly here, guys. So, when we talk about earth position, as Steve said, it, it, a lot of it depends on what, what you're doing. The first thing I want to cover just very, very briefly is when we talk about how far a signal will travel. Obviously, we've got frequencies that affect that. But the other thing that affects it just briefly, for example, is, is it a pipe or is it a cable?

9:11And if you imagine when we put signal onto an insulated cable, because the, the cable is insulated and the, the current, if you like, is within that insulation, it tends to travel much further. So, it kind of wants to run down that cable and find an earth point. When we put signal onto a pipe, for example, because the pipe isn't insulated, the signal bleeds off quicker. So, a few quick examples. Imagine I've got a lamp column here, looking from above, and a lamp column here, and just a very simple cable between them.

9:39If I hook up my Genny to this column, because this cable is insulated, the signal kind of has to run down it to this earth point, and then it returns. Alternatively, if I've got a metal gas pipe, looking from above, or a metal water pipe, if I hook up to this and earth it, because the pipe isn't insulated, the signal can kind of run off anywhere it likes. If you guys have done tracing before, I'm sure you can relate to, if you're tracing a pipe, a metal pipe, as you're walking along it, following it, your signal bleeds off quickly. You have to keep upping your sensitivity control.

10:11Um, if you're tracing a cable, you get, you, you tend to get a more, um, constant signal. Also, think about pipe size, guys. The bigger the pipe, the more surface area in contact with ground, the quicker your signal leaks off. Does, does that make sense to everyone, everyone, that, guys? Give me some feedback on that. Is it something you can relate to? So, let's just go back now to talking about the earth position a little bit more. And again, we'll use a lighting column as an example.

10:37Um, if, if we, again, I'm crap at drawing, guys, so, so, so forgive my drawing. If we have a lighting column here, and we hook up that Genny to here, if, if I put the earth out like this, a couple of meters, what we have to remember is that that earth wire is giving off a load of signal like this. So, in effect, I can't use my locator in that area. So, instead of doing that, if I have my lamp column here, if I hook up and keep the earth very close to it,

11:00I can now work round that column with my locator and detect that cable quite easily and work quite close to the column. Can you see that? So, by bringing the earth in a little bit closer like that, I can work closer to the column, in effect. Again, as Steve said, we, we don't need to get that distance out there with modern transmitters like we used to. Um, yeah, exactly, Jase. And also, guys, going back to pipes, think about high-pressure gas pipes. Anybody traced a high-pressure gas pipe? You can trace them for great distances. And again, it's insulated. It's traveling down it further. Yeah, okay, because it's an insulated.

11:37So, when, when we talk about earth position, though, it does have a, a more of an effect, I would say, on, on pipes. So, if we, if we look at again at that gas pipe scenario here, um, just give me a sec, guys. So, this is our pipe. If on the gas pipe we clip on and earth it close, we're actually encouraging more of our signal to jump off early, if you like. So, we don't trace as far. If we extend the earth out like this,

12:01you know, further away, we, we can potentially get more signal running down the pipe. Now, a lot of you said 90 degrees, but just think about this. When the earth's at 90 degrees like this, half my signal will run that way and half will run that way. You're effectively wasting half your signal because it's going in the wrong direction. So, instead, think about putting the earth at an angle like this, 45. We'd now get maybe 70 going that way. So, can you see we can angle the signal depending on the angle of the earth, basically? We can direct it.

12:21Also, think about other things as well. Which way do you want to trace? If I've got a house up here with a pipe going to it, if I put the earth down here, it doesn't really want to take that turn. It wants to carry on down the main. But if I put the earth up this way, it now wants to take that turn. But I probably won't get as much going down the main. Okay? So, all these factors are things you need to consider when you're putting that earth position in, guys. Does, does that make sense to everyone, guys? Do you accept that? You, you okay with that? So, we normally go into this on, obviously, a lot more detail on, on the courses that we do. Now, the other thing to consider, though, guys, and we're going to talk about this later,

12:55the downside of doing this, and we've got a classic example of this outside our office here. If, if we have a metal water pipe like this, and we hook the Genny onto it and earth it down here, what happens outside here is we've got a parallel utility. So, the signal now goes down here, and it returns along here. Yeah?

13:23Now, in reality, this should have a stronger signal on it because it's the one we're hooked up to. However, in the real world, this is a meter deep, this is 300 mil deep. So, what we end up tracing is the wrong service. But if we get the earth and earth it close, as Steve said, to the rim of the box here, we now get a completely different result. We've minimized the signal coming back down here, and we locate this one. So, so there's, there's pros and cons to it, yeah? If I extend it, I might get more signal, but I'm running the risk of it coming back down other utilities.

13:56I guess the important message with the earth is understanding what it does and, and playing around with it, guys. Okay? Is everyone okay with that, guys, yeah? Makes sense? Any questions on that? Um, and if not, I will hand you back over to Steve. That section was from the Genny bit that we normally do, guys, but I just, I just thought I'd throw a little bit in there.

14:20So, [no speech]

14:27[no speech] So, I'm going to do a trench. The other thing you may find is, like I said earlier on about earthing, you're struggling to get your earth pin in, maybe got no water. Another metal structure, drainage, anything in the ground that's not related to other services that are detectable, basically. So, I wouldn't use a comms lid or electric lid, but you can certainly use drainage lids or an old road sign, anything that's, um, in the ground that's going to give you an earth. Gully, something like that.

15:15But as Pete was just saying about forcing signal in certain directions, if you know or you've got an idea of where you want to trace, although we were saying keep your earth close, and a lot of you guys made some good comments there about, um, it does vary, and that's very true. But if you want to make your earth, sorry, make your signal go in a certain direction, move your earth in that direction. Obviously, you'd need to move your cable away because your earth lead cable is going to give off a big signal, or just accept the fact that in that area you're not going to get a very clear signal.

15:49I have used fences for earth. I don't recommend it. If it's a short bit of fence, uh, it may well be okay. If it's a long bit of fence, you've got to bear in mind these are always double-headed. So, by clipping onto a fence, you're also generating a huge amount of signal, and that fence becomes a very big induction antenna. So, that could also cause other issues.

16:20And on the right-hand side, feeder pillars, cabinets, anything at all with cables going in and out of it, don't use for earth, and don't use system earths. Always stick with the old earth pin. We always talk about independent earths. Anything that's not related to other services. Most of the areas have probably lost the earth pin within the first week, and they've probably got an old screwdriver in there now, but

16:43The other thing, these slides show the earth being, um, in the ground that way round. Most earth pins are like an L-shape. The reason for that is you can stick it in the ground that way round, so it's just underneath the surface, or even just laid on the ground and pour water on it. That's the only downside to a screwdriver. The, um, the rubber bit stops it from touching the ground quite as clearly, but

17:09Yeah, ab- absolutely, Luke. We actually talked about the last session about using a tree as an earth. Luke's just said he's used foliage as an earth, which is, which we, on the last one, we talked about that, using a tree as, as an earth, Steve. Yeah.

17:25Yeah, I, I, it was on a survey course once. We were struggling to get an earth, and there was a tree branch nearby, so I said to the guys, "We'll just use the tree," and they looked at me like I was mad. The thing you've got to remember is a live tree has got a lot of moisture in it, and that goes deep into the ground. So, yeah, you can do that. Um, you're going to probably need to use higher frequency, the lower frequency might struggle, but, yeah, you can use a tree, tree root, branch, something like that.

17:50So, as Pete said, keep your earth nice and close if you want to trace close in. So, in this scenario now, you can do a full 360 around that lamp column and work out which way that cable is going. As a generalization, the signal will travel from a lamp column, and you've got to bear in mind that this is predominantly aimed at how the, um, systems connected up in the UK.

18:18And in the UK, in most residential, city centers, you're going to have a cable feeding a street light column, which is fed directly off a main supply. That main supply is coming from a substation, so you can, in theory, and I've done it, not always, but you can clip onto a street light column, that will put a signal into the service, it will go down the service to a mains LV supply into a substation, and if you had an HV coming down here, that will go back through the earthing, and you'd be able to trace the HV.

18:55That slide kind of implies that you'll trace everything, which is not true, but it is a handy way sometimes of tracing other things when you're really struggling. When I was a teenager, we were allowed access. We were given keys. I mean, health and safety has changed a hell of a lot in the last 40 years, but I've worked in a 33 kV substation and was told not to touch anything. I guess you wouldn't get away with that nowadays, but

19:24Frequencies, guys. We've got there a graphical representation of quite a wide range of frequencies. And the one thing that when Radiodetection started producing multi-frequency machines, we said to the software engineer, well, they were, uh, hardware engineers in those days, but analog engineers, but nowadays software engineers. We told the engineers just to stick to one or the other, hertz or kilohertz.

19:53I'm guessing most of you guys understand this, but when we talk about low frequency, 640, 320, 512, whichever you use, is actually 0.6 kilohertz. Or if we're talking about 8, we're talking about 8,192 hertz. So, you can kind of see the confusion when people look at the numbers and they think, "Well, 640 is a bigger number than 8," not realizing that it's not actually 8, it's 8,000. This is something which I'm assuming most of you guys understand anyway, but

20:30That slide there shows, and the easiest one to count is the, um, the number of peaks or troughs. So, the 8 kilohertz one, there's eight peaks and eight troughs there. So, if you multiply that by roughly a thousand, you're looking at 8,000 cycles per second. And before we became European in this country, and, uh, probably in the States still have quite a lot of, um, frequencies listed as CPS, that's exactly how we used to measure it in this country, cycles per second.

21:00So, basically, if you look at that on an oscilloscope, you'd have your center line, if I could draw a straight line, which obviously I can't because I'm as bad at drawing as Pete, and so, 8,000 times per second, or 8,192 if you want to be precise, it alternates from a positive to a negative. I'm assuming you guys are still there because my screen just went blank for a second. You still there, Pete?

21:35Yeah, I'm still here. Okay. Um, we've never counted the others there. If anybody's really bored, you can if you want, but it kind of gives you a graphical representation of, over the same period of time, how much of a cycle has actually occurred.

21:58So, up at the 131 or obviously if we had 200k up there, you'd have lots and lots of cycles occurring over the same period of time. So, what happens is when you start using different frequencies, you end up with at the higher frequency lots and lots of energy initially. So, that means you've got lots and lots of signal. You don't need a lot of current, you've got lots of signal, but because there is so much energy initially, it dissipates very quickly.

22:27At the other end of the spectrum, at the low frequency, 256, 512 if you go to work in the States, we tend to use 320, 640 in this country, or one of the um CD frequencies, basically that doesn't divide by 50.

22:48Just jump in there, Steve, um to add to that, one of the problems that we often find in the UK is that we find a lot of surveyors out making use of the lower frequencies. They tend to stick to the higher ones, and as and as Steve said, what you tend to find with the higher frequencies, they seem to be working better because at the beginning, you tend to get a higher signal, if you like. It seems stronger um than the low frequency signal does, but as Steve said, it dies off very, very quickly.

23:14Um, the low frequency might not seem as good at the beginning, but it will certainly travel, travel, travel further, further down the, and um I think on the last one we did, we did a bit of a poll on what frequencies people use, and it was interesting how many people just use 33 or above. They don't tend to use the, the, the, the lower range of the frequencies. Back to you, Steve.

23:33Yeah, I'm seeing what Luke's put there. Sorry, I'm going to lean forward, I can't see it on my screen.

23:47Yeah, the thing, Luke, if you've, if you're using a comms frame lid for an earth, you've got a very good chance you're going to put a signal into that lid and then possibly into the cables below, because obviously with comms pits, both in this country, Virgin Media, predominantly, um, their stuff's very shallow, so you've got cables just below the lid, so you're going to get induction into those. Um,

24:14Going back to our frequencies and um what we've got on screen here. The best analogy that I can come up with is sound. If any of you guys have ever, I don't know, where I live, we often have um festivals down at the rugby club. It's about a mile away, and you can hear the music coming from the festival, but the only thing you can hear is the bass.

24:46So, the low frequency, and if you've been to a gig or a concert, you can feel the low frequency moving the air because it's, it's a much lower frequency, much longer wavelength. The high frequencies dissipate very, very quickly. It's exactly the same with a locator. It may sound very loud, very clear to start with, but it will dissipate a lot more quickly. The other downside to high frequencies, don't get me wrong, they are very useful at times, but the other downside is the fact that they will transfer and cross-induce onto other things a lot more easily.

25:21So, this symbol here is the symbol for no earth or a capacitive earth. Pete covers on his CAT and Genny course, and we're not covering today because I don't think we've got time, but he talks about PME in this country, which is the modern earthing system in the UK, where you don't technically have an earth at the end of a cable, it's on the network somewhere.

25:45So, if you put a low frequency onto a cable which is jointed and feeding a load of buildings, and it's PME, you won't get a signal traveling down. If you do, then there's a big solid earth. When I started in the 1970s, every house in this country, every building had a big solid earth. You put a signal onto an LV cable, and the signal would go down the cable, and it would go off down to the nearest big earth, which may be at the first property, it may be the middle property. But you don't get that effect anymore.

26:16But what does happen with the lower frequencies, and we're talking, we look at 8 and 9.8, those sort of frequencies, around about the 10 kHz range as being kind of a, a low to medium frequency. There's no actual definition unless you look in Wikipedia. But those frequencies should continue down the main and not down services, and very unlikely to transfer onto other things.

26:44If you start using higher frequencies, you get the bonus, the fact you can actually trace a service to a building. The downside of that is it's going to jump across onto adjacent services, as Pete was saying before. You can affect that somewhat by placing your earth away from it if you know there's something else there, but this is the downside. This is the main reason why avoidance devices like the CAT and Genny tend to have higher frequencies.

27:10This is something Pete covers on his CAT and Genny course, um but you've got in a CAT and Genny, the Genny itself is actually transmitting 33 and 131 kHz simultaneously, and the CAT's picking them up in the Genny mode simultaneously. With the vScan receiver and transmitter, the vScan, which is the vLoc equivalent, simultaneously transmitting 33 and 131, the receiver, you can switch between the two. And other manufacturers do the same thing.

27:44But those devices are more device, designed as avoidance devices rather than surveying devices.

27:52Steve, just jump in, um, uh, I think it's, as we were saying, it all depends on the area, how congested it is, uh, to not forget to try multiple frequencies. Um, Luke was just saying we use different frequencies depending on the utility we're trying to locate. Absolutely spot on, guys. And, and that's the thing with, with, with, you know, the training comes in, if you like. It's not, it's just teaching people what the different frequencies do, which ones might work, which ones might not work, understanding when to change frequencies and that kind of stuff, which you, you guys get. Um, and that's the idea of having this high-end kit, is you have all these frequencies at your disposal, and you can use um, any, any one of them.

28:31So, when I started in the 1970s, the location equipment that we used back then for surveying had one frequency, 3.4 kHz, or was it 3.142? I can't remember. Anyways, around about the 3 kHz range. We didn't have another option. And if I'm being honest, I think I probably located more things deeper with that old analog stuff

28:40Steve: For surveying, had one frequency. 3.4 kilohertz. Or was it 3.142? Can't remember. Anyway, it was around about the 3 kilohertz range. We didn't have another option. And if I'm being honest, I think I've probably located more things deeper with that old analog stuff than I've ever done with more digital stuff. [cough] The upside of the digital stuff is you can have [cough] a whole load of different options and frequencies. And...

29:11When Pete was in the office the other day, he had the old RD600 on the shelf behind him. That was the first proper multi-frequency machine that Radiodetection produced in the 1980s. That had seven frequencies from 1 kilohertz up to 130 kilohertz on the active range. Nowadays, I don't know how many there are on the 8100, I've not counted them, or the vLoc Pro 3, but you've got 30 to 40 different frequencies. You don't need all those frequencies, but...

29:41...a range of low, medium, and high is useful to have, and then you probably switch off the ones you don't use, or you just scroll past them when you don't need them. So, as a general rule of thumb, and don't forget this is just a generalization, low frequencies will give you a longer range, you get less cross-induction, it's a more of a locating frequency. High frequencies, they are very useful, keep on saying that. You get much more signal induction, you're more likely to pick up small cables. In the UK, most small comms cables...

30:11...Virgin Media is an exception, but BT, they're not usually earthed properly. I know in the States that's different. In this country, you don't generally get earths on the end of small cables. So, that means you're going to have to use high frequency to get a signal to travel down them. And it's back to Pete again. He's going to go a little bit on signals and aerials.

30:42Pete: Can you turn your screen share off, Steve? Steve: I should have done that, shouldn't I? Pete: Yeah. Sorry. Hi guys, back to me. So, we're going to cover a little bit now on on antenna settings, um, in particular, distorted fields and and peak and null, and then Steve's going to carry on covering some of the lower frequencies and current direction. Before I start with my slides, guys, I just want to ask you a question. Can anybody tell me the physical differences between a peak aerial and a null aerial? Not what they pick up or what they detect, but the physical differences. If you looked at them both, what difference would you see? Anybody tell me that?

31:24I'm just looking at Neil's comment, Sygma. Yeah, that's an old one. [cough] Maybe should have been a bit clearer with my question. [laughter] But, um, I'm going to run through it with you anyway, guys. When you when you have your locator on peak, and this is the same way that a CAT works, it's basically using, um, a ho- exactly, yeah. That's what I was trying to get at. Probably asked the question badly, Paul, but yeah, it's the actual it's the actual orientation. So, a peak aerial is horizontal and a null aerial is is is is vertical. Some locators might be might be a little bit different. When you're locating a signal, you've got your I'm I'm used to the old stuff like Steve, so I call it a needle, but you've got the...

32:10...you've got the you've got the signal strength meter, should we call it? Well, you'll hear me calling it a needle anyway. And as you walk across that that signal, that magnetic field, it peaks, you get the highest point, and then it drops again when you go past it. So, I'm sure you guys all understand that you're looking for the highest signal, and that should equate to where the utility is. So, what what the what the aerial is actually doing is it the signal response you get from your locator is actually based on the angle of the magnetic field passing through the antenna, okay?

32:43So, I'm just going to turn my screen share off so you can see me a little bit here. But, just just imagine that coil there. That's what the aerial is at the bottom of the locator, just so you can see me bigger. If you imagine my my knuckles as being that coil, and I place that, it's all reversed on here, so it's the wrong way. If I place that in the magnetic field, it passes through it. And and that's why, guys, I'm sure you're aware that if you put your blade of your receiver in in line with the utility, typically, you you don't get a signal, okay? So, it's got to go in 90 degrees, and then the magnetic field passes through. And and the way that it works is this, guys. When the magnetic field, the angle, is horizontal, the maximum amount of signal can pass through that aerial. So, that's why we'll get the highest reading, where it's horizontal. If the angle of the magnetic field was on a 45-degree angle like this, let's say we'd get 50% passing through. And if the angle of the magnetic field was vertical like this, none of it would pass through.

33:41Okay? Does that make sense, guys? Just just want to get some input into this. So, each section I move on to will only make sense if we understand each each part leading up to it, okay? So, that's how our how our peak antenna is effectively working. That's how a CAT works. So, if I just put my my my screen back on with you again here, what you can see here is the um the the peak antenna, the horizontal antenna. And here, it's, oops, get my pen going. Can you see horizontal? 100%. Over here, it's on a slight angle, so it's a weaker signal. Yeah, cool, guys. So, so let's let's effectively put that in the real world. This is a magnetic field coming off a cable. If I put the aerial here, I'm going to get 100%. If I put the aerial here, can you see it's 45 degrees? I'm going to get 50%. If I put the aerial here, again, 50%. So, that's why I get that peak response.

34:38What I also want you to see from that diagram, guys, is the highest reading, yeah, the 100%, which relates to the horizontal band, on this situation, is directly in line with that cable, okay? Next, let's look at distorted field, guys. So, in an ideal world, the magnetic field coming off an underground utility should be a cylindrical, just like you can see there. However, quite often, it gets distorted. Distortion is caused by many things: bends, T-junctions, multiple utilities, there's a whole host of things that can cause distortion, guys. And a distorted signal would look like this. Now, once again, using our peak antenna, if we look if we put the most horizontal part is probably about here. So, that's going to give me my 100. If I put the receiver directly over the cable, as you can see here, the angle's kind of 45 degrees, so 50. And over here, 50. So, my response now is like this.

35:38So, I'm going to mismark the cable. Anybody ever had that before, guys? I'm sure you have, where you've you've marked something up and it's in the wrong place. You get a mislocate, and it can vary. Does it make sense so far, guys? I will keep asking you for a bit of feedback during this so we can keep moving on to the next section. Okay? So, that's how we can get an inaccurate locate from a distorted magnetic field. Okay? That's how a CAT works, so it's we we do a lot of training with the guys on site who are who are doing excavations, and they'll often complain that they've mismarked things. Okay? Now, the difference between a null aerial, guys, is a null aerial...

35:50I will keep asking you for feedback during this so we can keep moving on to the next section. Okay, so that's how we can get an inaccurate locate from a distorted magnetic field. Okay, that's how a CAT works. So, we do a lot of training with the guys on site who are doing excavations and they'll often complain that they've mis-marked things.

36:08Okay, now the difference with a null aerial, guys, is a null aerial is actually vertical. Now, if anybody knows with a null aerial, what you actually, if we forget the arrows for now, because I know we've got arrows on there to make our life easier, but if we go back to the old-fashioned locators like the old RD400s, the null basically is where you get the minimum response.

36:28So, the idea of a null antenna is that you get signal when you're away from the cable and then as you come over it, the signal drops to its minimum. So, we get no signal where the cable is. And the reason for that, I hope you can relate to this, can you see the null aerial is vertical?

36:43Okay, so once again, I'm just going to turn my screen share off so I can use my knuckles to show you this. Imagine the null aerial being like that. If the signal was now vertical, the magnetic field angle was vertical, I'd get 100% reading, wouldn't I, from the null antenna?

37:01But when this magnetic field is horizontal like this, how much will pass through? Zero. Yeah? Any other angle like that or like that, I would get a response from the aerial, but when it's completely horizontal, I get a complete zero. And that's what your null antenna is referring to. So, here again, where the magnetic field, oh, I've done it again with my pen.

37:21Hold on, let me turn screen share back on. So, let's go back to here again now and look at the null antenna. Here we go.

37:33So, again, the antenna is here, the magnetic field is horizontal, zero. But if I put it over here, it's not, um, it's passing through it. Makes sense? So, let's look at the real world again. If I put the null antenna here, because it's horizontal, I get zero. But if I put it over here, because it's now angled, I kind of maybe get 50. And then over here, um, again, so in the midst, I get 50. So, the null response is more like that.

38:03Okay. So, does everyone understand how a peak and null antenna works? Okay. And do you also see, guys, that the peak and null antenna is going to point to the same place? It's, in effect, it's picking up the same thing. A peak antenna is giving you the strongest response where the magnetic field is horizontal.

38:23Okay. And a null antenna is giving you the minimum response when the magnetic field is horizontal. Okay. Have we all got that, guys?

38:36Okay, so let me ask you a question then, guys, and forgive the delay. When we have a distorted signal then, if the peak and null antenna are effectively pointing to the same place, why do they give different positions?

38:49Yeah, what's the answer to that, guys? Why, if they're actually pointing to the same place, do they give different positions on a distorted signal? Can anybody tell me?

39:12See if anyone can get that one.

39:23I'm not sure if you don't know or you're just not answering yet, or it's a delay on there, guys, so I'm going to carry on and see if any answers come in. And the reason for it is the position of the antenna. So, if we look at a typical locator, we're going to ignore the top aerial for now, your peak antenna, which is horizontal, is here.

39:47And the null antenna is here. Okay. Okay, got that, guys? So, in other words, the null antenna is higher, all right? So, let's have a look at this magnetic field again.

40:07On this one, which is undistorted, the peak antenna is detecting this band, if you like. That's our 100%.

40:22The null antenna, which is higher up, is giving the same position. Even though it's higher up, the angle is still horizontal passing through it. But let's look at a distorted field. Look at the difference. The peak antenna is here, but the null antenna is higher up, so it would equate to here. Does that make sense, guys? If you look at it, the deeper something is, the further away those horizontal bands come. And because the peak and null antenna are at different heights, that's what gives us that offset.

40:52Does that make sense to everyone? And this is also, guys, me and Steve spoke about this last week, this is also why sometimes the peak and null response from different locators is slightly different. It depends on the distance between the antennas. Some are closer than others on it. Okay, so is everyone okay with that, guys? It's obviously quite technical this bit, but, um, I hope you understood that.

41:14So, that's why when we have a distorted signal, guys, what we actually get is this. We get the true position, the peak position, and the null position.

41:25Okay, and one of the, one of the interesting things is, guys, you know, we get this for beginners quite a lot, is if peak says it's here and null says it's here, a lot of people think it's in between. And it's not. It's on this side of the peak. So, you kind of get cable, peak, null, or cable, peak, null.

41:43One thing that you will always notice, guys, is which is always furthest away? Null. And the problem with that is that because we use these little left-right arrows on null, people often think it's more accurate, and it's not. Okay, it's not. It always goes further away. There was a rule basically saying that you could kind of work out this position by, some, some theories say half this distance, some say a third of this distance. I would not bank on that, guys. There's been many a situation where that's not been true.

42:10You'll, you'll usually get that layout, but this to this, I would honestly say I'd be very cautious about putting any exact figures on that distance. Um, I hope that was useful, guys. I hope that, that, that made sense, um, and now you understand about the different, um, peak and null antennas in the machine. Some of the locators work slightly differently, guys, but that's in effect, um, what we get from distorted signals. So, just to summarize, if peak and null are in the same place, it generally means we have an undistorted signal, generally means we're going to be accurate. And that's why we do that peak and null test before we take a depth reading. If peak and null are separated, we've got distorted field.

42:47And then we need to look at correcting that, guys. This is the other thing that we find, is that people kind of accept that and start guessing where it might be. Let's look at changing frequency, changing earth position, uh, changing connection points, but the first thing we must do is try and correct that signal, not just locate with a distorted signal, if possible. Um, hopefully that makes sense, guys.

43:08Just before you go back, go back to your, um, one where you drew your triangle, Pete, on your, um, distorted field, cuz to draw. Yeah.

43:29Pete: Absolutely. And this is another point, guys, that we talk about in more detail, because there's multiple ways of of looking at distorted, um, signals coming off it. We use peak and null as one. But what you tend to find with an undistorted signal, you get an equilateral triangle. I'm crap at drawing triangles. With a distorted signal, you might get more kind of like that, if that makes sense, guys. And we can do this with a basic CAT as well. We can look at the the angle of drop-off.

43:53Pete: And just before I pass you back to Steve, Steve's going to talk start talking now about current direction and current measurement. Um, I'm not sure if you guys have used these before, um, so anyone used current direction out there? And I want And we want to talk about the importance of of these high-end features on your locators, because again, we feel that they're underutilized. So, I'm going to show you an example, which I've already touched on, and then Steve's going to relate to this as he talks about the next section.

44:22Pete: A very simple example, a plan view looking from above. I've got my pipe, if you remember. Okay, and I've and I've hooked my transmitter up to the pipe and put the earth here. Okay. And then I've got a a parallel utility. Now, in theory, with a locator, whatever we hook up to should give us the strongest signal. If we've got a return signal that's bled onto something else or coming back down something else, in theory, that signal should be weaker. Okay? So, what we've got here is we've got signal traveling down here, and we've got it kind of coming back down here. Going to keep it nice and simple, guys, yeah?

44:58Pete: If both those utilities were at the same depth, we would generally get a stronger signal on this one. However, that's not always the case, is it? So, like I said before, let's imagine that this is a meter deep, and this one is only 300 mil deep. What could effectively happen now is that this one from the surface is giving us the stronger signal. So, we end up tracing the wrong one. Okay? This is a problem that we have. This is where current direction and current measurement come in to help us figure this out. And I'm going to pass you back to Steve, who will expand on current direction and current measurement. So, I hope that section was useful for you guys, what I've just covered.

45:41Pete: You ready, Steve? Steve: Yeah, sorry about that. Pete: Your screen share back on, mate, and it's back over to you. Steve: Yeah. [no speech]

46:10Steve: I don't know if you guys can still hear me, but, um, it's hanging at the moment. Apologies for this. It's just suddenly gone, um, greyed out. Are you still there, Pete? Pete: Yeah, mate. Still here. Still here. Steve: Yeah, mine's just hung for some reason. Sorry about this.

46:40Pete: Can see your slideshow, mate. So, I can see you. Steve: I can't see anything. Pete: Do you want to jump back in? Steve: Hang on a sec. I'll just see if it works. It's just I can't get rid of the, um... Here we go. Pete: Yeah, it's working, mate. Steve: Yeah, okay. My second screen's just hung for some reason. Never mind. We'll carry on, guys. Current direction, signal direction, or signal select. So, RD, Radiodetection, developed current direction...

47:12Steve: ...it was originally in the old RD400 range, so 20-plus years ago. And one of the main issues we always had, and this mostly came out about through, um, working with AT&T in the US, was trying to actually make sure you were tracing the right thing. And over distance, even the lower frequencies, you did get a point where you started to get return signal...

47:40Steve: ...and it was sometimes very difficult to determine which was the right one. So, RD engineers developed current direction, and it was a methodology where you could actually trace out normal, but you had a separate... I don't know if you guys, and my second screen's locked, so I'm not sure I'm getting any responses, but, um, I don't know how much you guys use CD, SD. CD and SD is pretty much the same thing. SD is vLoc's version of, um, current direction, they call it signal direction.

48:10Steve: And SIS is signal select, which is, uh, a much wider range of frequencies doing pretty much the same thing. Very useful in congested areas or for long-distance tracing, and you want to make sure you're on the right thing. A side line, one of the things I do in my business just to keep, um, keep the bills paid and keep the grey matter working, is I do cable fault detection. And I would never consider taking a machine out to do a cable fault without CD or SD or SIS.

48:40Steve: And the main reason for that, the first and number one rule of cable fault detection is that you locate the cable. And you've got to be on the right cable. I've had pretty much standard arguments with people who are convinced they know where the cable goes, and when you've got a CD or an SD or an SIS signal on it, you can categorically say, "You're wrong. The cable doesn't go there. It goes where I'm telling you it goes." So...

49:18Steve: You can only apply current direction or signal direction using direct connection leads or a clamp. SIS on the vLocs, you can, and they probably won't like me for saying this because they they do actually sell an SIS clamp, you can actually get the SIS frequency to, um, work using a standard clamp. You can't with the RD kit. It's got to be a dedicated CD clamp. And that's it. Here you go, Pete.

49:46Pete: Steve, just want to jump in a second, guys, just to be clear for anyone that doesn't know is, CD's a frequency, in effect, and it's a low frequency. So, the same limitations apply. You have to be able to get that frequency onto the utility. And to do that with a clamp, you need that big whacking clamp. Um, even with connection, you know, it treats it as a low frequency, you need a good connection. Steve: Just keep talking to me, Pete. I'm just going to have to, um, close down the browser because it's gone off my screen altogether now. Pete: Oh, we can still see you a little bit. Steve: Can you? Pete: Yeah.

50:10Just keep talking to me, Pete. I'm just going to have to close down the browser because it's gone off my screen altogether now. Oh, we can still see you a little bit. Can you? Yeah. I can't. Um... You might have to re-log in if you leave. Sorry about this, guys. I can't see the screen. It's just gone off. Yeah. Just re-log in, Steve. I'll hang on till you log back in. Guys, just bear with us for two secs. If you want a quick toilet break, um, just run to the toilet. Yeah, my browser's hung. We can still see you, Steve, but, um, you might want to leave the room and just reconnect. I can't leave it now. I'm going to have to close it down manually. And he's gone.

51:21There we go. You just have me now, guys. Any Any questions, guys, while Steve's just just reconnecting? He's going to run through, um, current direction with you when he when he gets back. As I just mentioned before, um, we have to understand that it is a it is a frequency.

51:46You are still there, guys, yeah? I'm hoping nobody else has disconnected. We've got 62 on, and when there's 62 on, the delay's a bit worse. So, when we when we're running these for real, if you like, there's a paid course, we'll be limiting it to kind of four or five people, which makes it a little bit easier.

52:08He's back in the room. Hello, hello. The problem we have is that Steve doesn't mix very well with technology anyway. Did you hear that, Steve? Sorry. Nothing to do with me, it's the system. Bring back Windows 95, that's what I say.

52:49Yeah, okay. That's... Sorry about that, guys.

53:08So, if you've got the RD kit and you're going to use, um, CD on cables, you're going to need one of those things. The downside to that thing is it's only 3-inch diameter. So, if you're working in areas where you've got larger cables, um, the Vivax make a larger 4-inch, um, 100 mil CD clamp. The only downside to any of this is it's all very expensive accessories. None of these manufacturers send it out as standard bit of kit, but...

53:41So, on the RD kit, 8000, 8100, you're going to scroll down to the frequency, um, you're going to choose. They tend to use in the US, um, 512, um, 256. And we started talking about that when, um, when Pete jumped in with some other, um, observations. One of the main issues with any low frequency machine in this country or anywhere in Europe, I'm guessing you guys know this, electricity is generated at 50 Hz.

54:29So, if you get any multiple of that, it's called a harmonic. So, any multiple of 50 is kind of easy to work out: 100, 150, 200, 250. So, if you get a multiple of that, then you're going to get a harmonic. So, around about the 512 or let's say 256 region, if I can get my pen working again...

55:00So, fairly simple math. You multiply that by five, you've got 250. It doesn't take a huge amount of frequency shift to get that up to close to 256. You shouldn't really be getting 51 Hz, but you're probably not getting true 50 Hz in this country. So, what we tend to find is around about the 256 frequency in this country and Europe, we get a huge amount of interference from cables, just standard power interference. And it's not really interference, it's just picking up the harmonic.

55:40And conversely in the States, because of electricity being generated at 60, you start multiplying that by 10, 11, 660, 600, so you're getting close to the 640 range. So, in the US, we tend to not use anything that's close to being divisible by 60, and the same in the UK and Europe, or anywhere where it's a 50 Hz system, it's a multiple of 50. Yes, Pete.

56:17Yeah, I was just going to say, so that's why, guys, um, when we when you talk when you hear low frequency being used in the States, they generally use 512, um, and 256, um, for the CD. And in the UK, we use 640 and 320. Hope that makes sense. That's why we have different low frequencies for the US and the UK. Yeah, yeah, um, is it worth...

56:42So, the the the clamp basically would go around an insulated cable when it's exposed. So, um, easy example is imagine a a trial hole with a cable exposed in it. They don't work round lamp posts. Um, there was a big thing that went round about this with the bloody gas industry. They started calling them bloody column clamps and putting them round lamp columns, and and they don't work. You The only way you do it on a lamp column is is by going into the column, taking the door off, and then clamping round the cable inside it, which most people aren't qualified to to do anyway. So, it's got to go round the cable. Generally speaking, that cable has to have an earth both ends, again, to create that that that circuit. Um, you can sometimes get round that using using high frequency. Uh, back to Steve again, who'll carry on with the CD.

57:24So, the the key thing with, um, the CD or SD or SIS is ensuring you are actually getting the signal in the right direction. I know it's a bit of a contradiction in terms because you don't have a directional signal...

57:52The carrier frequency is the higher of the two, and the identifying frequency is the lower. So, you'll always find it's half the carrier frequency. So, 640 in the UK or Europe if you're using that one, half of that's 320. On the 8100, if you guys are using that one nowadays. And the other thing is you've got to make sure you've got the right model. Um I would go to full screen, but I'll probably mess it up. So,

58:20RD8000 PDL. In the 8000 range, there's only two machines that have CD. That's the PDL and the PTL. There's quite a lot of different um models of 8000, but there's only two can actually um receive CD. The TX10 transmitter is the only transmitter you need. Um I know that again there's a wide range of transmitters, but I'd stick with the high-power transmitters.

58:56A TX1 and a TX5 look exactly the same as a TX10. The 1, 5, and 10 is the power output. And if you've got a TX1, you don't have CD. So, and you've only got one watt of output. If we've got time, we'll talk about transmitters and how to get more power out of them, as well as messing around with earths and earth placement. There are ways of getting more power out of a transmitter if you're struggling.

59:24So, you choose your CD frequency, and you've got to make sure that your current direction is in the right direction. If this is working.

59:42Actually, I'm going to skip to that slide, and we'll come back to this one in a second. The next one's a a video from RD just explaining a little bit about it. I'll turn up the volume as well so you can actually hear it a bit more clearly. Current direction allows you to identify your target line amongst a number of parallel utilities by applying a specialized current direction signal from the TX transmitter. A directional arrow is displayed on the locator screen, confirming that you are tracing your target line. An icon on the locator screen shows you which frequencies support current direction. It is always good practice to reset current direction before use. This can be done by a sustained press of the F key from any of the current direction frequencies. To verify current direction, you can build a small circuit using the red and black direct connection leads from the TX transmitter.

60:20Set a CD frequency on the transmitter and point the receiver toward the red clip. The CD arrow should be showing current flowing toward the red clip. If this is not the case, use the current direction reset option, and the arrow should then start pointing in the direction that the current is flowing. To verify, switch to the black lead. The directional arrow will now reverse.

60:57Going back one slide, guys. That's the sort of... Can I just jump in a second there? Yeah. Just turn your screen share off a sec. So, guys, just to um jump in before Steve gets to the technical side of it, remember the example and the problem that I gave you before. Um I'm just going to I'm just going to redraw it very, very quickly.

61:25Which will hopefully help anyone that's new to CD understand what it's doing. You remember the problem we had. We had this pipe here that was a meter deep, plan view, and then we had this other utility that was quite shallow, for example. And then we'd hooked up to this, and we had signal traveling up here and back here. Now, we're trying to locate that pipe. The problem we have is that we've got multiple signals, and we're not sure which is ours, okay?

61:52So, whereas before this one had the strongest signal on it, what will happen now, the arrow you just saw on the locator will point away from the transmitter. So, when you put your locator over this one, it'll point away. Any return signal will have an arrow pointing back. So, even if I had multiple utilities all with a return signal on it like this, everyone of them would have an arrow pointing back. So, let's say, what have we got, the four

62:20four signals. One of them would point away, the rest would point back. And that's how we start identifying that we're on the right target line. Is everyone with us so far on this, guys? You're understanding the benefits of of CD? And Steve's going to again talk about it in a little bit more detail. Um on that note, guys, I'm sorry, I have to leave you. Um I have to go to a to a to a very important meeting. So, I'm going to leave you. Um Steve will update you on the rest of the sessions that we've got um at the end. If you've got any feedback on today's, guys, uh drop me an email. Hope it's been useful so far, and I'm sure you'll enjoy the rest of it. Um and I'll pass you back over to Steve, um and I'll see you all later.

62:58Thanks, mate. See you soon. Just while you've got me in um large screen, it showed on the RD video pressing and holding the frequency key on the 8100 to reset CD. On the 8000, it doesn't do that. What you have to do is you have to go into the sub-menu.

63:30I'm seeing this backwards, I'm guessing you guys are as well. Sub-menu, momentary press, and you scroll until you see CDR. That stands for current direction reset. The one thing I don't think it made clear on that video is whenever you do a current direction reset, you've got to make sure that your back is to the transmitter, and this bit, it did say point this towards the red lead, but you've got to make sure that this is always pointing in the direction you think the cable is going.

64:09So, what I tend to do is check it on the red lead initially, but you've got to make sure that that is pointing in the direction of the cable or the pipe, not back towards the transmitter. If you do a CD reset with it in the wrong direction, you're going to get the arrows the wrong way around. In his last little scenario, you kind of twig straight away that something's not right because you'd have loads of away-facing arrows and one facing back, and that would kind of make you realize that CD's the wrong way around. But the easiest way is always on the red lead. The difficult thing with CD is when you get a signal clamp. The main reason for that,

64:48a signal clamp

65:08so that way, with a signal clamp with an arrow on it, you always know to point arrow downwards as the cable goes into the ground or goes away from transmitter. If you're not sure, your best option is to put it around a cable where you can actually see where the cable is going and make sure the arrow is pointing in the right direction.

65:28Get the screen share back on again. So, the thing with the 8100, it's very quick to do a CD reset. With the 8000 PDL or PTL, you've got to go in the sub-menu to do it. On the vLocPro3 series, it's a momentary press,

65:52I think it's I key and then momentary press of antenna key, if my memory serves me right. Having been in lockdown for a while, it's been a while since I've been using the kit, so. So, that little slide there, this is the universal symbol for a transmitter. Except I've lost um my drawing tools, here we go.

66:17So, that's the universal symbol for a transmitter. So, this would be your red lead connected to a cable. This would be your black lead connected to earth. And this is simulating an excavation trial hole, cable pit, whatever, where you've actually got three utilities.

66:39Let's say they're all cables, they're all the same color, they're all the same size, and you want to know which is which. So, you walk across it with your receiver, you might be getting multiple signals. Usually, with CD and low frequency, you're going to have your strongest signal on this one. But, possibly, you're getting fairly similar signals.

67:01The benefit of CD is you're looking at your screen, and you're going to have your arrow pointing away on this one. And on the other two, your arrow points back.

67:19If you guys are using the vLoc2, you don't have an arrow, but you do still have the same thing. So, in your compass direction indicator, you've got two hemispheres around your compass direction. And basically, that equates to this hemisphere lighting up, and arrow back relates to this one.

67:42So, instead of an arrow, it's just the semicircle hemisphere, whatever you want to call it, lighting up as your direction indicator. On the vLocPro3, you've got a nice big arrow shows up on screen, so you can't miss it. I don't know if you guys, I'm assuming everything's back up and working again now. I don't know how much delay there is on there.

68:02How much do you guys, or do you guys use CD a lot, or at all, or never? One of the questions we we asked at the first session we did last week was what frequency did most people use for tracing? And I guess it kind of depends on what you're doing, but do you guys have a preferred frequency? Do you use CD?

68:22While you're scribbling your answers down if you can, if you notice on this trial hole excavation, cable pit now, you've still got three cables. You would assume that the middle cable is still the right one. As you can see from that scenario there, they've now changed position.

68:42So, this is the one with the arrow pointing away. The other two cables, arrows pointing back. This is one of the benefits of CD, and this is why I always use it on cable fault detection. And because every time you do a cable fault, and there's a a very good book, if you hunt it down on the internet, written by an old um

69:11CEGB engineer, Barry Clegg. And he opens up by saying, "There are only three types of cable fault: a complete open circuit, a complete short circuit, and everything in between." And 90% of what we trace is the third one, the ones that are in between. But the most important thing is you've got to know where that cable goes, and you've got to be 100%

69:36certain you know that cable is the right one, and it's the right um route that you're tracing, otherwise it's complete waste of time. So, that's why I use CD a lot. It's also, it just takes away the confusion. There will be times when even CD causes problems, just because of other signals, mostly um 50 Hz or 60 Hz in the US.

70:04So, Stefan, yeah, you've got a normal signal clamp, so if you're using RD kit, you can't apply CD. If you're using vLoc's kit, you can apply SIS. Um Yeah, Martin, yeah. CD's not something you have to use all the time. It's one of those, like every other tool in your armory, it's just a useful thing to have.

70:35You may be on sites where you don't often need to use it. On the RD8100 and the Tx-10 with the latest version of software, you might notice that there's a 4 kHz and 8 kHz CD. That's very, very useful when you can't get the low frequencies to travel, or you're struggling with 50 Hz or 60 Hz interference.

71:00Um if there's anybody from vLoc's on here, they can tell me the highest frequency on the vLocPro3 with SIS. I think it's around about the 35 kHz range. So, they've they've taken SIS beyond the normal frequencies up into the higher frequency range. And that's again down to one of the problems we tend to have with the low frequencies.

71:20When I was talking about frequencies earlier on, low frequency is always preferable in identifying or tracing situations where you've got congestion. But the downside is 50 Hz or 60 Hz interference, and you need more power from your transmitter. So, you may find that you're trying to use low frequency or CD, and you're just not getting a clear enough signal.

71:46So, both RD and vLoc's have now made receivers that can receive higher frequencies and still have the benefit of CD or SIS, which is the same thing.

72:05So, this is very similar to the slide that Pete then drew in. To answer your question, Jason, um, will CD work on HV? Yeah, you're going to have to have a CD clamp, as in a thing. Um, and some HV cables are too big.

72:26This is something that we said all along when RD produced the CD clamp initially, that the clamp was too small. And so Vivax have got a 4-inch, I believe, 100 mil, um, CD clamp and an SIS clamp. Um, receiver clamp, you can get a CD receiver clamp, or you used to be able to, but I'm not sure you can anymore. You can certainly get a CD stethoscope.

72:55Um, in this country, although we've used it numerous times for cable identification, it's not an approved method. The main reason for that is there are, um, instances when you can get it wrong. Certainly with a signal clamp, you can get the clamp the wrong way around. That's the simplest way of getting it wrong. So, in the UK, and different countries will have different, um, legislation, but in the UK, there's only one approved method for cable identification.

73:20And that's, um, putting a transmitter across two cores, which is shorted out at the far end, and using a very simple receiver with a small stethoscope-type aerial, which you run along the cable and you pick up the twist of the cable, the lay effect as it's called. So, we don't tend to use CD as an identifier, although you can. Mark is saying yours is fro- frozen. I'm guessing you're talking about your screen, but, um...

73:50Um, Stefan, to answer your question, I don't, I have got the, the RD price list, but I think you're looking at around about £600 to £700 in the UK. So, I'm guessing that's, um, if you're overseas, um, sort of exchange rate at the moment is probably around about the same, $600-$700 or Euros for a signal clamp. So, the scenario we've got there up on screen now, your transmitter would have been applied down here somewhere...

74:21...to this one, with your earth pin, and you're getting return signals on underground services and on crash barriers. Any long metallic structure just acts like a normal cable or pipe, any conductor. So, you do get signals from crash barriers, it's a known issue. If we get time, we'll talk about that a little bit later on, but...

74:58Pretty much every machine nowadays has got current measurement, and it was, um, initially sold as a, a method of identifying before current direction came out. If you guys have got any specific questions, I know I'm skipping around subjects, um, only because mindful of time, we ran out of time last time, so, um, if you've got any questions, by all means pop them up on screen, and I'll try and answer them as we're going through.

75:28So, the idea of current measurement is you're looking at the signal that you've applied, and the machine's popping up on screen with an indication of which has got the most current. So, in the scenario there, it's not the most accurate graphical scenario because it probably wouldn't be very accurate anyway, but the idea is you've got your target line down here, you applied your signal, this is not using CD now, this is just using CM, current measurement.

75:58And you've got a stronger signal here than on the one you think it is. And you've got a slightly weaker signal over here. So, the idea with current measurement is you're actually looking at the current response and saying, "Well, that's 13," these are made-up numbers, by the way, "that's 27, and that's 19." If those utilities were about double those distances apart, then that would probably be okay, but that close together, I certainly wouldn't rely on current measurement. It is a very useful function, though.

76:30Again, we use it on cable fault detection, pipeline monitoring, um, and just looking to see where signals split. So, Pete does, um, quite a lot of sessions on CAT and Genny throughout the week, basic type tracing stuff. And although you don't with the standard CAT, you do with the vScan receiver, you do actually have current measurement on the vScan receiver, but on the standard CAT, you're just looking at signal strength, and you're looking at where your signal's changing and splitting.

77:00So, the idea is you put a signal onto whatever you're trying to trace, you pick up a receiver response, and then you look at your current. When I was a teenager in the 1970s, we didn't have current measurement, we had the old-fashioned needle responses, had a big moving-coil meter with a gauge on it from 0 to 100. And we were taught to religiously set the thing to 70%.

77:30So, you set your needle to 70% and you watched it. And if you got any change of signal when you went back over it, that indicates that something's happened to your current. So, it may drop down to half, it may drop down even further than that, it may go up. But once you saw that change of signal, you knew something was happening. On the modern receivers, you've got current measurement. I haven't got an 8100 with me, so I've only got a standard 8000.

78:00So, on the 8000, your current measurement is indicated down here where depth would normally be shown. And to switch between the two, you press and hold the aerial button. So, if you've not seen current and you want to get current on screen, you hold the aerial button down, and it switches over to current. If you've got an 8100, which Pete had in the background when he was, um, with the Sygma, on the 8100, you've got current and depth shown simultaneously. So, on this side...

78:30...where you've got frequency on the 8100, it alternates between frequency and current, and on this side you've got depth. And on the vLocPro3, you've got depth and current, again, simultaneously shown on screen. So, as I said to you before, the idea is it shows you where your signal's going and what's happening to your current. I wouldn't use it, as that slide says, if things are close together, but if you've got a reasonable separation between multiple utilities and you're still getting signal on three or more of them, theoretically, the strongest amount, or the highest amount of current will be the correct pipe or cable.

78:50I wouldn't use it as that slide says if things are close together, but if you've got a reasonable separation between multiple utilities and you're still getting signal on three or more of them, theoretically, the strongest amount or the highest amount of current will be the correct pipe or cable.

79:10Yeah, Bill, you've put on there you use it for locating cable joints. Yeah, um, so you follow your signal, your signal will always change when you get some sort of connection on the cable, a joint. Sometimes it's very obvious, sometimes it's not.

79:30But this scenario or this slide here explains how current measurement works. So, you've got a 90% signal strength reading on your screen, you've got a depth of 0.6, and your current measurement is showing 25 milliamps. You've walked down the route of the cable and it's gone a lot deeper, it's gone down to a meter down, so your signal strength dropped from 90 down to 30%.

80:00If all things are equal, your current doesn't change because that's how it does it. It's calculating, and don't forget, it's it's a made-up number. You're not actually picking up 25 milliamps because that's impossible to actually measure, but, um, it's giving you an indication of how much current is being given off by the pipe or cable. In that situation there, it's signal strength dropped dramatically, but your current stayed the same.

80:22If, and this is maybe what, um, Bill's talking about, if this was a cable and we had a joint here, and we had a cable going off over there, your 25 milliamps, if all things are equal, could end up being 12 and a half going that way, and 12 and a half going that way. It's again something we tend to use where cables are jointed and you're looking to see where your signal is, and what's happening to your signal.

80:54So, in simple terms, your signal's coming down here, 25 milliamps. On a plastic insulated cable, the people were talking about, you're going to get very minimal loss over distance, unless it's a really long distances. So, a few hundred meters, you're not going to see a massive amount of loss of signal unless there's a joint or a connection, or something's happened to it. So, you can monitor which way your signal's going by looking at your current measurement. I'm hoping that makes sense to you guys.

81:26It's also something that we use on pipelines. I spent a lot of work, um, in the 1980s and '90s, um, with a guy who was the the guru in this country for pipeline corrosion control, guy called Graham Gusey, worked for British Gas and, um, lectured all over the world on corrosion control. If you guys have ever done any, um, pipeline, um, monitoring,

81:53the old tried and trusted technique was what's known as a Pearson survey or CIPS, Close Interval Potential Survey, where you're putting probes in the ground and you're looking at, um, the earth soil potential, which, um, with a a coated, protected pipeline, and I can't draw straight lines, so you've got your pipe, which is like just like a cable, it's insulated, and it's steel, and it's welded, so electrically, it's as good as you're going to get.

82:27But let's say a farmer's put a fence post, which in this country, it may be the same in the US, but in this country, a lot of damages tend to happen on farmland, even though the farmers know they're there. So, he's stuffed a fence post in the ground and he's taken off a big chunk of the insulation here. So, let's say this was per kilometer. The old-fashioned technique

82:54would be that you'd walk along the route with your ski poles, your probes in the ground, and you're looking at the potential measurement between the pipe and the ground around it. This was obviously very time-consuming, took a lot of man-hours to do this, especially on long-distance pipelines over distance, um. So, we learned very quickly that you could use low frequency and use current measurement to look at a linear loss of signal.

83:24So, if you've got a chart of loss over distance, it tends to be reasonably linear. These numbers are a bit low, but let's say for simple maths, we'll stick with them. 100 milliamps, 1 km, 80 milliamps, 2 km. So, this is fairly linear, we're getting 20 milliamp loss per kilometer. And the other thing about this is you don't have to walk the entire route. You jump in your car, van, truck, and you drive to a road crossing or a point where you know roughly that you're another kilometer away, or, in the States, miles away.

83:58And you suddenly find that between three and four, at our 4 km point, we've now only got 20 milliamps. So, at this point here, we've lost 40 milliamps. So, if you map this in loss, 20 milliamps, 20 milliamps, 20 milliamps, 40 milliamps.

84:27So, you now know that between kilometers three and four, we've got a significantly higher loss of current. These numbers will be higher, but anyway. What you can then do is you can then walk that kilometer looking for any obvious indications, farmers putting fence posts in, um, it could be another utility crossing it. You can use an A-frame, a PCM device, every manufacturer, most manufacturers anyway, make machines for picking up these contacts. Even just a standard locator will probably pick it up.

84:50So, that's where current measurement's very, very useful. I've done lots and lots of, um, tracing like that. I don't know if you guys do pipeline monitoring or anything like that, but that's where you'll find current measurement useful. We debated where to put this slide in, and it's been moved around a few times, um. This was before the 8000 came out, about, so it was in the old RD4000 days. Um, I went up to Scotland with a surveying company who were being tasked with remapping

85:28um, Scottish Water's assets, and they'd had some issues with, um, where they'd marked where they thought the pipe was, and it turned out not to be correct. So, they they decided it was a training issue. There was a combination of factors. I went out with this surveyor, pretty experienced guy. In the UK and the US, um, Metrotech was a very common manufacturer. Metrotech are now owned by Vivax, big, big manufacturer, um, very well respected in this industry.

86:00In the US with big, wide open spaces, the old Metrotech 810 was a great bit of kit. Um,

86:14In the US with big wide open spaces, the old Metrotech 810 was a great bit of kit. Very widely used. If memory serves me well, it was 83 kilohertz. So quite high frequency. Auto gain.

86:33And in the UK, a lot of guys working in the water industry were using Metrotech equipment. In tight Glasgow streets, same as anywhere in the UK and Europe, the high frequency and the auto gain wasn't quite as good.

86:52So I took this guy to one of the sites he'd had an issue with, and he, I just left him to it. I said, "Show me what you're doing." So he connected his transmitter up as the slide shows there. He put his earth into a grass verge over here.

87:08So going back to what we'd said earlier on about earth position and what we cover on day two of my survey course, talking about electrical circuits, where's the electrical circuit there and what's the issue with that? I'm assuming you guys are still there because I can see some numbers up on screen, so.

87:29Um, the other obvious thing to say about water pipes, and certainly in the northern part of the States, this was an issue that I found, and I'm guessing if any of you guys are from the northern part of the States, you'll know this, or Canada, because of the permafrost and temperatures in winter, you can have to have water pipes at significantly greater depths. So, I moved south when I lived in the States, I moved to Houston, so freezing up of water pipes wasn't so much of an issue.

88:01Yeah, Jersey, you're absolutely right. So, you clip onto a water pipe, and this is what this guy did, I think it was a hydrant or a valve, too long ago, I can't remember. And it was close to the road edge. And the other thing to say about water pipes...

88:25In this country, there's a very common ductile type pipe, and it's called a Tyton connection. So, I'm a bit like Pete, not very good at drawing. So, you've got like a male-female configuration, and inside the bell housing is a rubber O-ring. And your other bit of pipe sits inside it like that, and it sits on that rubber O-ring. So, you've got an issue with electrical continuity. Ductile's not a very good conductor. So, let's say these are five-meter sections of pipe.

88:57The other issue, besides the fact we've got these rubber O-rings, this pipe is bare metal anyway. So, your signal travel... Yeah, Neil, you're right. You've got your earth near to other services. This is a major issue with this. Remember AC, alternating current, something we cover on the survey course, explaining about AC and DC, not the band. Probably find it more interesting than me rambling on, but anyway. So, we've got signal going in all different directions. We can't stop it from doing that.

89:27And because this is a bare metal pipe, instantly we're getting loss. We're getting signal return going across here. There becomes a point where the path of least resistance for this current, whichever frequency we're using, is to actually travel down adjacent cables. So, we've now got signal traveling in both directions on adjacent cables.

90:05Let's say for simple maths, we're getting 100 milliamps from our transmitter. And if all things are equal, that means we've got 50 milliamps going in both directions. And let's say, again for simple maths, at each joint we lose 10 milliamps. We've straight away lost 10 milliamps at the first joint. You can see what's going to happen, guys. And that's assuming we're getting no loss, which is also not true, but for the purposes of this, it just makes it a bit simple.

90:48Yeah, Michael, that's, that's the problem. Um, well, that was his initial problem, combined with the fact he was using 83 kilohertz and auto gain. So, if you guys have ever seen the old Metrotech, you've got a center-sprung needle, and it peaks one side and it's continuous the other side. So, as you go across it, you're looking for that needle to center out.

91:21You have no gain control on that thing. The machine automatically adjusts the gain. So, as he was tracing on down here, he was getting the correct location, correct location. Machine's automatically adjusting the gain, so he's not noticing the fact that the signal's dropping. You get to about this point, and his signal starts to do this. Because what he's got over here is he's got about 5 milliamps returning, but it's not just returning, it's traveling in all directions on the other cables. In this case, let's say electric cable.

92:07So, as he started to gradually head across the pavement in this direction, I said to him, "You've got to stop now." He said, "Why?" I said, "Because you're no longer following the cable, the pipe." He said, "I am, because that's what I connected onto." I said, "Firstly, you've got another valve hydrant up here." He said, "No, that's offset." I said, "Mate, this is the problem you're having. You're using high frequency, and look where you put your earth."

92:30Um, Michael, you said use the gully. That's exactly what we did. Yes, that's standard, thanks, Neil. Yeah, Neil, you're thinking about depths being, um, unreliable. If we get time, we'll talk about depths, um, and depth measurement. Um...

92:58The main factor with any machine, doesn't matter which one it is, is you've got to have a nice, clear, undistorted signal. And you guys understand about peak and null, peak's being true with you. One of the simplest ways of working out, um, distortion... I have no allegiance to either manufacturer. I've got mates who work for both companies, Vivax, RD. I'm just looking for the classic screen on here.

93:10understand about peak and null, Pete's been through with you. One of the simplest ways of working out, um, distortion. I am not leaning to either manufacturer, I've got mates that work for both companies, Vivax, RD.

93:36So, if you guys can see that screen, although there's no signal at the moment, one of the easiest things you can do with this thing is just look at the color of the bar. So, when you have got signal, if we can get something that'll give me any kind of signal at all.

94:00So, with this one, you're going to see a red screen, a blue screen, or a green screen. If you've played around with these things, you'll know this. A red screen means bad signal distortion. Blue screen means a little bit of distortion, and a green screen means you've got a very, you might not be able to hear me on that, a green screen means you've got a good signal. It's a very, very quick and simple way of checking for distortion.

94:27You can do the same with the RD kit on peak and null by verifying your peak and null positions. It's entirely up to you which machine you prefer. Um, but that's, that's key factor with depth. Um, you may well be right in what you're saying, Neil, about, um, repairs and connections. The other thing is, we do cover this later, but while we're talking about it, obviously, size is important when it comes to, um, depths.

94:58Because your machine is calculating to the center of the magnetic field. RD used to make a device called a Vectorbar, which was a great bit of kit. And the first thing that you did before you started tracing was you put the size of the pipe in. So, if you're tracing a 24-inch pipe, you told the machine it was a 24-inch pipe. The machine would then compensate for the, um, the 12 inches between there and there.

95:34I don't know what you guys do. On most survey drawings that I've seen, companies put on their drawings that depth to EM is here, depth to sonde is here, and depth with GPR is there. You have to bear in mind that if some of you guys did Mike's GPR course yesterday, that might not be always strictly true with the GPR because you might actually be getting the bottom of the pipe, not the top of the pipe. And similarly with the sonde, if you push it a long way, the thing tends to coil up sometimes, and you might end up with your sonde appearing somewhere.

96:14Of course, that's important if you're in, um, a large 3-foot diameter or 1-meter pipe, but the thing I'm guessing you guys do know, this is always your, besides distortion, this is the critical thing. So, you need to know that. And most surveyors tend to just put down whatever the machine says, but the bigger the pipe, obviously, the bigger the error. So, if that's a 36-inch pipe, you got 18 inches. For those of you working in metric, that's about half a meter discrepancy, if my math is correct.

96:47So, a 1-meter diameter pipe, metal pipe, big, big pipe, is going to be 500 mil out, always on the depth, if the depth is correct. Anyway, going back to, um, our little scenario here. This is where I had taken our RD4000, which had CD on it. Um, the first thing, as, um, Michael said, moving the earth to gully did help a little bit, but it didn't solve the problem completely.

97:21We then put my RD4000 on it with CD. We still had the same scenario where the signal eventually did transfer enough onto the cable that we got a stronger signal. The other thing you've got to remember is the cable's shallow, or shallower, than the pipe. So, a water pipe down around about 800 down, electric cable 400, it doesn't take long for that signal to suddenly become stronger. But with CD, even though it's an AC signal, this is when you are looking at your arrows, and this is where you are getting this effect.

98:00So, your arrow indication is always going to be pointing away. Your return signal is always going to be pointing back. So, even though we ended up with stronger signal on the electric cable, we knew it was the wrong one because of the arrow direction. And this is again where current direction, signal direction, or CD is very, very useful. Um, there is an old tried and trusted technique, which I was taught as a kid.

98:28And when I worked at Radiodetection, when we, we did utility location in those days, um, when we had all our kit sent up, it was a surveyor kit with every conceivable accessory you could imagine. And one of the most useful bits of kit was a 300-meter extension cable. And what that allows you to do is that.

98:53So, talking about my stage two surveyor course and electrical theory and electrical circuits, what's your electrical circuit now? On the previous two slides, the electrical circuit involved using the earth ground as part of your circuit. And this is the bit that people tend to forget about. You've put your red lead on what you're trying to find, you've put your black lead in the ground to the earth. That whole mass of ground is part of your electrical circuit, and anything else that happens to be in there also becomes part of it.

99:25So, if you're working where there's old tramlines, rail lines, that's part of your electrical circuit, fences, um, even a large vehicle parked alongside you will carry some of that signal and become, if not part of the circuit, certainly inducing some signal. But what happens in this scenario here, guys? Yeah, Bill. What we call a double-ended connection. It's the old-fashioned but probably best technique for tracing anything you could possibly ever want to trace. There's an obvious downside to it. Firstly, you need a 300-meter cable or longer.

100:08Secondly, you've got a long bit of cable with trip hazards. There's one very good reason why we run it across the road and down the other side, and that's to get it away from all the other services. Because that cable is generating a huge magnetic field. If we're using low frequency, as you know from experience or or what we've been talking about, the lower frequencies are less likely to induce into things. In the old days of the analogue kit, they used to say

100:20Because that cable is generating a huge magnetic field. If we're using low frequency, as you know from experience or what we've been talking about, the low frequencies are less likely to induce into things. In the old days of the analogue kit, they used to say, um, move the cable three times the depth. With digital kit, I would say make sure it's further away.

100:47That cable, within reason, could can be as long as you want. I had a guy, um, got his own survey company, been on my course, he rang me up one day, he was trying to find a a pumping main rising main, uh, or in America, a force main. And I said to him, "Have you got two points of contact on the pipe?" He said, "Yeah, but they're about, um, 600 meters apart." I said, "Well, get yourself about a kilometer of reasonably good quality copper cable. Doesn't have to be very big."

101:18But you're not going to get much loss down that cable. So, in this scenario here, your circuit is down through your pipe and down through your return. And, obviously, alternating 8,000 times per second if you're using 8 kHz. But this is the scenario now. You don't get as much loss through the joints. You will still get loss.

101:49But let's say our 50 milliamps, you might find now it's around about 45 milliamps, 40. You get to a midpoint, 35, and then your signal starts going back up again. As far as an AC circuit is concerned, that's pretty much connections at both ends.

102:16You might not always get all the way back to your full amount of current because of little bits of loss, but you'll end up with this scenario where your signal starts to increase as you get towards your next connection point. So, if you imagine this is now a kilometer apart, and you've got 1.2 kilometers of cable, I know it's time-consuming, and this is something the surveying industry doesn't have a lot of, but if it's something you've got to find, and I did the same thing at GCHQ, um, down in Gloucester, tracing cables.

102:49If it's something that you've just absolutely got to find, this is by far the best way of doing it. You guys might not have tried it because you probably haven't got the cable. I believe, um, I was told by Pete on my last course, RD stopped making that long cable. I mean, you can go out and get one yourself. I joke with guys on my course that, um, one day I'll start a web shop, we're going to call it Steve's Survey Shop, and all these things you'll be able to find, um, I've been saying that

103:12for about the last 15 years, and it's never happened, so it probably won't happen in future, but I believe Vivax are now, um, selling a long, um, extension cable. Most of the kit come with a 5 or a 10-meter extension earth, which is sometimes handy, but you obviously can't do that over long distances, but it's one of those things, like every other tool in your armory, it's handy to have once, keep it in your car, your truck, your van, keep it with you because you never know when you're going to need it.

103:36I've used it in the last couple of years, probably once or twice, but it's a useful thing to have. And if you can't get it from a manufacturer, you can go online, buy yourself some pretty decent single-core copper cable. Obviously, the longer it is, the further your signal's going to get. "Could you use two Gennys, one at either end?" No. Um, the main reason for that, Neil, is what's known as a beat frequency.

104:07And you'll know this when you come across it. If you've ever been on site, two of you guys tracing out together, and you're both using 8 kHz, what happens is the two frequencies end up beating. And what happens then is your signal is a bit like is a bit like a Genny signal, it start an old-fashioned Genny signal, it starts pulsing. And the problem with using two Gennys is you've still got the same amount of loss in both directions. So, um, this is still,

104:40albeit time-consuming, and you do need the cable, a much cheaper way of doing it. "Locatable rodder?" Yeah, you're talking about, um, putting a a locatable Cobra-type rod down a non-metallic pipe, I guess, and connecting on both ends. Yeah, that'd work great. The other thing is you can work a lot deeper with these type of techniques because you're not relying on earth. The earth is no longer part of your circuit, it's the cable. So, if you're struggling with things that are deep as well, this will help dramatically in that scenario.

105:16So, that is a double-ended connection, guys, um, old-fashioned, tried-and-trusted technique. The only thing you need is a very long cable. So, um, look, maybe in the next 15 years, Steve's Survey Shop, I seriously doubt it'll ever exist, but, um, or go to the manufacturers and pester them for one, or just log online and get a long bit of cable on a drum. In this country, you can get empty drums from, um, most hire-stroke-tool supply companies, and just put a load of cable on it.

105:58The thing to say with doing that, um, this is something I noticed with the RD kit, you do need to uncoil all the cable because the RD kit struggles with the inductance of the cable wrapped up. So, you've got to take it all off, it's a bit of a pain. The Vivax transmitter copes a lot better. What happens with the RD kit is you don't get, even though you've got basically, um, as much as you can, a perfect circuit, with the RD kit, you don't get a lot of current. So, you've got to uncoil all the cable, and I know that's a pain, but, um,

106:34could I potentially make a long cable? Yep, absolutely, Lou. You can stick it on a on an old toilet roll, have to be a very big one, but, um, any old bit of wood, drum, anything, you can wrap a bit of cable around. So, most of these, um, in the UK, you can get from the likes of CPC, um, Toolstation, they they sell empty drums, and then you can just put your own cable on it.

107:22Yeah. Um, what we do on these courses, and this is the same as the survey course, we kind of teach you the purest ways of doing it, and you you it's the sort of thing you don't need to use every single day. You might not use it more than once or twice a year. You guys might, same as CD, you might find that most of your tracings are done fine with 8, 9.8, 33, even higher frequencies. So, what we're trying to do is give you some pointers on how to, if things are not working out how you want them to, or you

107:30use every single day. You might not use it more than once or twice a year. You guys might, same with CD, you might find that most of your tracings you're doing fine with 8, 9.8, 33, even higher frequencies. So what we're trying to do is give you some pointers on how to, if things are not working out how you want them to, or you're struggling, or you're thinking how on earth am I going to find that. So any pipe where you've got two valves, a valve and a hydrant, two hydrants, 3-400 meters apart,

108:01this technique, obviously assuming it's metal, will work perfectly. You just need a big long cable, and hope people don't trip over it. Um, we're getting close to 2 hours, guys. We've got some slides to carry on with. It's entirely up to you guys. I'm happy to carry on. Uh, we've still got 53 in the room. I'm guessing most of you guys are still awake, hopefully. Um, if you want me to carry on, we'll do a little bit more. If numbers start dropping, or you guys have got to go off and do other things, then we'll wrap it up.

108:39Stick your comments down if you want me to do a few more bits on, we've got some stuff to do on sondes and capacitance. We don't have to do it, it's entirely up to you fellas, but, um, if you're happy to carry on, we'll carry on. If, um, we, last session we did, we didn't realize, but there was a 2-hour, um, limit on the software, and it cut us off, but Pete's now upgraded the software, so if you guys are happy to stay, I'm happy to talk. Um, I have another session, so I can't talk too long, but

109:12I'll do a little bit more with you guys, and then we'll, in fact, let me just check, because, um, my apologies, guys, I can't remember when my second session starts. Yeah, it does, it starts at 1:00, so I'll, I'll do about another 10 or 15 minutes, guys, and then, um, I'm doing utility networks at 1:00, so you guys are welcome to hop back in again and join me, or if you, uh, sheet off and, uh, enjoy the rain in Bristol. Well, hopefully you've got a bit of better weather, but. So this slide you're looking at here,

109:45we cover on, um, days two and three of my surveyor course, doing electrical circuits, so we get guys drawing out electrical circuits, and the good thing about some of them is that they don't always work because the circuits aren't great. I'm just reading Francisco's comments. Um, I know if you, you guys have got contact through Pete, so, um, he would have sent you the, um, the joining instructions for this, so I, I guess your best option is to email Pete with your, uh, questions and what you want to, um, know a little bit more about. And any comments as well, guys, um, send them off. Um,

110:28so you've got your transmitter, which is in this scenario, the battery, and you've got your red and your black lead, but you've got no connection. So it's not a completed electrical circuit. So theoretically, there is no current flow. But this is a technique that's again been around for years. It's never been very well documented by the manufacturers. And it's something that we show people on even a standard CAT and Genny course, just guys out there every day working in the streets, using a simple CAT and Genny.

111:05The symbol there that you're seeing, hopefully on screen, is the symbol for a capacitor. And that's where you've got two conductors separated by an insulator. And also, the higher the frequency, logically, the more often it does it. So you've basically got your red lead, and in this scenario here, that is a satellite or aerial cable running down the wall of a building, plugged in the back of a TV or an aerial, uh, satellite receiver box.

111:41And underneath the insulation is a conductor. Underneath the red cable is a conductor. So you've now got two conductors separated by insulators. So you've now got a capacitor. Um, Stefan, to answer your question, I think we might be doing one more, but you'll have to, um, keep an eye on Pete's, um, LinkedIn page. I, I share on my LinkedIn page as well, so if you guys are on LinkedIn, have a look, or I'm not sure if he's putting these up on the, uh, Sygma website, but it's certainly on the, uh, on the LinkedIn pages.

112:17So as you can see from there, we're using water for earth. For this to work, you do need to use high frequency, so you're probably 33 kilohertz and above. And what's happening there is the signal is capacitively discharging from the red lead into the satellite or aerial cable, which is then going into the back of a TV or aerial receiver, which is plugged in the mains. So it's a very simple way of tracing electric supplies. So you find a cable on the outside of a building which is going into the building, which is plugged into, that could be an outside light, it could be, um, an aerial cable like that.

112:54If you're in the middle of a city center, um, there could be an outside light on a building, and you'd wrap your red lead around that outside light. You've got, inside the light, a conductor. You've got the gap between the red lead and the light as an insulator, so you've created a capacitor. So that's what we call capacitive coupling. And this is again where your high frequencies are very useful. In this country, we've got a lot of cables, BT cables, communication cables running down wooden poles. You can do it anywhere in the world where you've got a cable running down a pole that's got a guard, a shroud around it, so you can't get a clamp around it.

113:36The red lead, although you can't see it, up here, would be just tied in a knot round there, just so that it hangs down close to the cable. You've got your earth pin in the ground down here somewhere. And as part of an electrical circuit, you need two, so there's one of your earths there. This cable goes off and eventually goes back to a cabinet somewhere, because in this country, there's a BT cabinet or comms cabinet, there's an earth there, that's the universal symbol for earth, and there's an earth here. And there's your two earths.

114:24And the signal is transferring from the red lead into the BT or comms cable through capacitive coupling. You may notice when you're looking at your, um, transmitter that you're only getting 2 or 3 milliamps. You don't need more than that. Um, couple of milliamps will suffice at high frequency. And the one thing with all these transmitters, if you press the arrow up button to increase the amount of current, although the bars increase, if you notice the current doesn't increase, then all you're doing is overdriving the

114:40not. Um, couple of milliamps will suffice at high frequency. And the one thing with all these transmitters, if you press the arrow up button to increase the amount of current, although the bars increase, if you notice the current doesn't increase, then all you're doing is overdriving the transmitter and running your batteries down. It won't damage your transmitter, all it's doing is just eating your batteries. Another point to make, guys, and I'm sure you know this, pretty much all surveyors do, with

115:11any of these transmitters, always, always get rechargeable batteries. I'm not trying to sell the manufacturers um more expensive systems, it just saves you a whole load of hassle. With modern rechargeables, you get a lot more capacity than you can get out of alkaline batteries, and you'll find the batteries last a hell of a lot longer when you're on site. And for whatever reason, and none of them, none of the manufacturers seem to be able to tell us this,

115:37the battery indicators seem to be a lot more accurate with the rechargeables. If you've ever had the um misfortune of using NiCads, if you remember that far back, NiCads were terrible. But modern lithium-ion or nickel-metal hydride batteries, rechargeables are brilliant, so I would strongly recommend you do that. And you don't need to drive lots of current when you're doing this because the high frequency does it for you.

116:04Pete covered quite a lot of about peak and null aerials. The only thing to say is you've got an 8100, I don't know what you guys are using, you've actually got five aerial settings. You really only need peak and null. Or peak or null. This is very difficult to explain, and it's not easy to explain when you're actually on site, but that is the aerial configuration for an 8100.

116:38A lot of guys like using peak and null because it shows that on screen. So you're getting your peak indication using your bar indication and your signal strength, so your bar indicator, numbers,

116:57and your null is indicated by the arrows. The thing you have to be aware of, and I've had a go at RD about this, is that with an 8100, you've got peak plus.

117:11When you get used to it, it's very, very good. But initially, if you swap from an 8000 to an 8100 and you press the aerial button and you go from peak to what you think is peak and null, it might not be peak and null, it might be peak plus, where the arrows are actually mimicking the peak.

117:37So what you've got to do when you've got an 8100 is make sure if you think you're in peak and null, you are actually in peak and null. And to verify that, when you're in the peak and null setting, so you've got both peak and null indications on screen, you hold down the aerial button for about a second, and in the bottom right-hand side here, it'll say null or guide.

118:07Because when it's in null, you then know you're in peak and null mode. And when it's in guide, it's in what they call peak plus mode, where the arrows mimic the peak. I know this probably, if you're used to it, makes perfect sense, and if you're not, it probably makes no sense at all, but basically, you can be confused by the fact you're getting peak and null in the same place when you're actually not because you're not in peak and null mode. My biggest complaint,

118:30and I've had a go at RD about this, is the box shows exactly the same symbol, whether it's in peak plus or peak and null mode. You can change that in the sub-menu. You can go in the sub-menu and change which one it defaults to. But just get used to the fact if you've just changed over from an 8000 to an 8100, you may not be in peak and null mode, you might be in peak plus. Um,

118:55guidance mode, which they also have in the peak and null mode just to confuse you even further, is basically MetroTech mode. If you guys have ever used a MetroTech, it's exactly the same display as a MetroTech. They obviously can't call it MetroTech mode, so they call it guidance mode, but it does exactly the same as a MetroTech. It's a center position needle. If you go left, you get a constant signal, if you go right, beeping, other way around, and it behaves exactly the same as a MetroTech. Auto gain.

119:21If I were you, I'd switch it off unless you like MetroTech mode and you're in a fairly congested area. Broad peak, I use it all the time for cable fault detection, but if you're not doing cable fault detection, I'd turn it off. It says there, used to detect and trace very weak signals, for example, deep utilities. This was true in the analog days, this is not true in the digital days. Um,

119:49in the old days of the electro-location kit, we used to press and hold the um depth button and that used to switch it on the bottom arrow and keep it on that. So it went into single arrow mode. On the 8, uh, 6000, uh, sorry, 600, you used to be able to switch it into single aerial mode. So with analog machines, it was very, very good. Unless you guys know different, I've never managed to get it working very well on the digital machine, but it is useful for cable fault detection. So on my machines, it's usually left switched off, but you guys can switch it off.

120:21Some people prefer to look at the peak and null separately, so it's entirely up to you whether you have peak and null enabled together or you just have peak and then you have null, it's entirely up to you. The one thing that Pete didn't explain with a, a null aerial, and we'll use his knuckle scenario here,

120:41so this is obviously directional. It can only detect a signal which is coming from this orientation or that way. But a null aerial, it's omnidirectional. The signal can be coming from any orientation flowing through the aerial. This is one of the other issues with the null aerial, the fact that it's omnidirectional, it has no direction. The way that you get the arrows on the screen is little sub-aerials either side which indicate the position with the arrows, but

121:10as Pete also said, a true null, and this is what a lot of people don't realize because they tend to just look at the arrows, a true null is where the signal response goes to zero and then rises up to a high setting. So if you're not getting a true null, it's dropping down from maybe 80% down to 30%, not a true null, even though the arrows might seem to be pretty precise. You want to see that signal disappear completely and then rise back up again. But, strictly on, this is all the purest stuff, this is not

121:40you guys probably don't have a lot of time to do this, so. So you've got your arrows, you've got the impression of a much greater accuracy, and the response is quicker. If you've got an 8100, you're going to get arrows on peak if you're in the guidance mode. If you've got an 8000, you've just got a signal response which rises and then falls, hence the peak terminology. And the variation

121:50...greater accuracy and the response is quicker. If you've got an 8100, you're going to get arrows on peak if you're in the guidance mode. If you've got an 8000, you've just got a single response which rises and then falls, hence the peak terminology. And the variation can be quite sluggish when it's deeper. The other thing is that's also a function of frequency. So, with lower frequency, you're going to get a slow response...

122:21...than you are with a high frequency. If we sum up, we'll go again. This is a classic example of distortion and it's predominantly power mode. In the background there, you can see a scar. The power reading is giving me two indications about a foot, 300 mil, either side of the actual position. So, there is actually nothing out there apart from that's where the field is. Directly over the scar, nothing.

122:58Signal again. This is not a fault of the machine. This is just where the magnetic fields are. Every machine would give exact same indication. And that is where we were tracing. Two triplex 11kV cables and a low voltage side-by-side in a trench. Indications in the wrong place.

123:26This is one of the downsides of using power. Useful frequency to have, but very commonly nowadays, huge amounts of distortion. A lot of guys are getting this where you're getting readings in the wrong place. The interesting thing about that site is when we use radio and we induce onto those cables, the indications were spot on. So...

123:55Traditionally, we only switched between peak and null to verify depth. And when the peak and null responses weren't in the same position, we didn't bother with depth. That's probably a much better indication than the one I tried to show you, um, holding the vLoc receiver up. So, you can see from the classic response, a red indication. So, if you guys have played around with this, it's very quick and simple. Although that's in non-mode...

124:33...you've got a red response indicating distortion. So, if that was green, you know you've got a good signal, clean indication. Blue, a fairly, it's very, very close to being spot on. The other thing I've noticed with the vLoc...

124:50...and you guys have switched around between different machines. And like I said earlier on, I have no allegiance to either company. I have friends who work for both manufacturers. Um, I would always recommend before, um, anybody shells out their hard-earned cash on this, um, equipment, borrow a bit of kit from either manufacturer and try them both side-by-side. That's always the best way. See which one you prefer. They probably won't like me saying that, but, um, that's the way I'd do it. Try both machines side-by-side.

125:22I do find with the vLoc Pro 3, just that color screen makes it so much quicker to look at distortion levels. So, um, we are kind of running out of time, guys, and I need to have a quick break before I start my next session. Most of the manufacturers, certainly, um, the PDL, PCL range of RD kit and the, um, vLoc Pro series will do depth in power and CPS frequencies. If I were you, I'd ignore it.

125:55We spent a long time convincing the engineers to take depth off power. Because in the old days with the analog kit, the depth button just worked. So, you could press the depth button and it would work in any mode, even though it was useless in power and radio, it did give an indication. So, we managed to get them to take it off in the digital days, and then they put it back on again. So, um, I would strongly recommend that you don't use depth in power.

126:20And if you guys have used CPS, um, again, we're running out of time, but, um, CPS stands for cathodic protection system. It's basically just a power harmonic. So, its inaccuracies are going to be probably as bad as power inaccuracies. Every manufacturer sells it as a way of finding high-pressure pipelines, which in the middle of nowhere, it is. But having said that, in the middle of nowhere, a standard CAT would find a high-pressure pipeline in power or radio mode.

126:50So, CPS does not work well in congested areas because you'll just pick up power signals. So, in the UK, that's going to be 100 Hz, and in the US, it's going to be 120 Hz. And in the, um, congested area in the middle of a town center, city center, on 120 Hz, you're going to pick up, um, power cables. So, active tracing of high-pressure pipelines is always your best option, using a transmitter and low frequency.

127:21And if any of you guys are remotely interested, that's how it calculates depth. So, obviously, the distance between the two aerials inside the machine are fixed, and your depth is proportional to that. So, as it gets deeper, that ratio is going to change. As it gets shallower, obviously, the converse happens. And you've still got to remember the size of your pipe. Small cable, it doesn't make a massive amount of difference between there and there. But a large pipe, obviously, it does.

127:53Guys, I'm running out of time. Um, I appreciate you guys have stayed to the end. Still 44 people on there. Um, thanks very much for your attention. How do you check the distortion in power and radio? Um, in power, you've got to kind of accept the fact that there's always going to be distortion. What you can do, Jeff, is you can put it onto one of the harmonics. Um, so, with the vLoc Pro and the 8100, you can, um, switch to 150, 250.

128:23The machine then acts like it's picking up an active signal. So, you then get peak and null, um, you can get the color display on your vLocs. Um, or you can say is generally expect to find distortion in power and radio. You can't really check in radio. Um, but certainly use the harmonics on the, um, 8100 and the vLoc Pro series machines if you want to see how really badly distorted... What I would normally say is modern cables, it's going to be very badly distorted anyway, so.

128:57Thanks, guys. Any comments, please, um, stick them on, um, the feedback, which I don't know much about, um, because I'm no PC expert on this, um. I'm going to have a quick five-minute break, grab a cup of coffee. Um, if you guys are staying for the, um, network session, um, you're brave, but...

129:00on um the feedback, which I don't know much about um because Pete's the expert on this um I'm going to have a quick five-minute break, grab a cup of coffee. Um if you guys are staying for the um network session, um you're a braver man than me, having to put up with me for that length of time, but thank you for um your attention.

129:22I think we'll do one more of these um before um hopefully everybody's out of lockdown and uh stay safe guys out there.

129:50Have a good one, guys.