Summary

Grounding is one of the most misunderstood aspects of motorsport wiring — and one of the biggest causes of electrical issues. In this webinar, you’ll learn how to design proper grounding systems that prevent noise, ensure reliable sensor data, and keep your entire electrical system performing as it should.

00:00 Hey everyone, welcome to today's webinar.
00:02 I'm Caleb here at High Performance Academy.
00:04 It's great to have you along.
00:06 Today we're going to talk about grounding.
00:08 It's a pretty common topic.
00:10 It's a common place for mistakes and issues and it's a common place for some confusion as well.
00:16 So, hopefully we can clear some of that up today.
00:19 Got a bit of the demonstration on the bench here that I'll be able to go through and show you a bit of an example of some bad grounding and good grounding.
00:26 Also while this is a live webinar remember it is recorded, so if you have to jump away you can watch this later on and it will be in our archives.
00:33 And hang around to the end for our Q&A, so if there's anything that you've got a bit more of a question on you can ask it then and I'll do my best to answer.
00:41 I do ask that you just wait till near the end.
00:43 I'll give you a bit of a prompt with the questions just in case I answer some things naturally along the way.
00:49 So, let's get right into it.
00:51 What is grounding and why is it actually important? Well, for starters we need a return path for our current, our electricity.
00:59 So, we have obviously our positive side, our 12 volt, could be 24 volt, 5 volt, whatever voltage it is it needs a return path back to wherever it's originated from.
01:09 In our case for an automotive it will be the car or sorry the battery or the alternator.
01:14 And it's very important that we get that return side good as well as our supply.
01:19 A lot of people often look at their supply and think and really concentrate on that making sure they've got the right sizing for the right current, the length of that wire and, so on.
01:31 And then it comes to the negative side the return side and they just go yeah that'll do and plug it in or twist it around a bolt or something and wonder why they have problems later on.
01:42 So, it is definitely just as important as our positive side and for things like sensors it can be almost more important.
01:50 There's a common fault that you'll sometimes find called ground offsets, we'll show a bit of an example of that later.
01:57 And what that can do is not necessarily look, like an issue it can present as a fully functioning sensor, but something like your ECU or a dash or PDM that is reading that is actually reading the wrong sensor value than what is actually, being measured.
02:13 Which obviously when you know our computer is controlling an engine to some pretty intricate mathematical equations those sensors need to read accurately.
02:23 So, let's jump over to my little display here and the overhead and I'll give you a bit of a run through of what we've got going on.
02:31 So, I've just got a simple 12 volt power supply, I've got it set to 13 volts at the moment.
02:37 It'll also show us our amps at the bottom there, show us our current draw.
02:41 That is just wired in here, I've got it to a switch bank which is going to a just a pretty generic I think it's a Honda taillight, indicator, park and brake in one globe dual filament and then I've got my reverse light over here which is currently wired up as a park.
02:58 So, that's all wired up the positive side as normal.
03:01 Ground side I've got wired up, most of it is to the bank over here, but I've got this switch over here which is a good bad switch and that is going to swap between a good earth and a bad earth just to you know show us an actual issue, so we can demonstrate something useful.
03:21 So, just going through that now, indicator works as it should, it doesn't flash because there's no, flasher relay.
03:26 Park light, as I said I've got my reverse as park as well.
03:29 We've also got that brake, so we have a look there we've got the dual filament, so everything is working as it should.
03:37 So, there's no problem here, but let's swap over to a bad ground.
03:41 I'm obviously not going to tell you straight up why it's a bad ground, but I'll show you this is a good example of when a ground that is bad can sometimes you know present in a really weird way or not in a intuitive way.
03:55 Usually we kind of just expect it to not work, but in this case if I go to use my indicator my park light comes on.
04:02 If I go to use my park light that one doesn't work, that one does work.
04:06 Brake light is on a separate circuit, but it's pretty dull.
04:09 So, yeah not what we kind of expect when we want to use especially our indicators and you might have seen this before sitting behind someone at some lights particularly with trailers sometimes they're wired up with a bad ground and you'll get a similar situation to this.
04:24 You'll see indicator flashing on the car, but then the park light or brake light is flashing on the trailer itself.
04:30 And to explain what is actually going on here I've got the ground from my indicator and my park brake globe wired to the left hand side here.
04:39 This bank here which is then wired into my switch and then from there goes back to my main ground and power at the power supply.
04:47 But the ground point here is going to a bolt here which has my wire twisted around it in a perfectly fine way like I'm sure that's going to be a good earth.
04:56 But you know most of us will look at that straight away and be like okay that's a bad earth but sometimes it might not be quite that obvious.
05:04 And when you're you know when people are looking for an earth generally what they might do and I mean I do the same thing is generally you will find a point that you know is a good earth, so my power supply is obviously my main earth over here and then simply use a multimeter to buzz out or continuity test between points in the loom or chassis to find a ground.
05:26 So, this one over here that's a obvious good ground.
05:29 I know that one's a good ground.
05:31 It's going to my that side park light.
05:34 If I go over here got another good ground another good ground we got continuity everywhere.
05:40 So, I've got this switched to bad and my lights aren't working, but I've got continuity from my ground to my ground wires at the light.
05:47 So going by just that you'd think okay my grounds are good everything is working perfectly.
05:53 But as an actual fact we know that is not exactly the case.
05:57 So, the first thing we'll look at here is a good way to actually test four grounds and a good ground.
06:03 The best way to do that is generally with a voltage drop test.
06:07 So, when we have a circuit we pass current through it.
06:11 Anywhere we have resistance which is absolutely everything has resistance.
06:15 Wire has resistance, our globes have resistance, ACUs have resistance.
06:20 It just depends on how much resistance they have and things like a globe that will have more resistance than our wire and that's why we get our filaments start glowing they're resisting the power flow current flow that creates heat and light.
06:35 Our wires they won't generally have enough resistance to cause us a dramatic voltage drop but in a bit of a separate issue if your wiring is very long you do get to a point where you do get a voltage drop from too much resistance from that long length.
06:51 That's one of the reasons we say you know you got to keep an eye on wire length not just your wire sizing.
06:58 So, to test a voltage drop in this kind of situation what we're basically looking for is our voltage is going to naturally drop over any resistance.
07:08 So, when we power up a light I'll show you in a good working order first.
07:12 I turn my light on when we check a comparison our voltage at our power supply here we should be getting if I set that to the right function our 12.85 volts.
07:22 So, it's a little bit lower than my 13 at the power supplier there might just be connection issues that the actual power supplier will delete themselves but we've got a good 12.7 volts.
07:35 Now, checking voltage drop we're not going to check normally when you check voltage you check you know from a good common ground and then you'll check voltage at certain points.
07:46 To check voltage drop you're going to check across two points that you want to see a voltage drop at.
07:52 So, my two wires that I have on the left here are my indicator power and ground.
07:56 If I place my multimeter across these two I'm going to get 12.78 volts.
08:01 Now, what this is saying is that I have a voltage difference or potential across those two points of 12.78 volts and that's because pretty much all of our voltage is dropping across that globe.
08:12 It's working as normal the resistance in that globe is our only main resistance in that circuit and that's where our voltage is being used.
08:21 If I compare that ground I can then compare to my ground over here and what I'm doing there is checking voltage drop from that wire all the way to my ground.
08:31 Now, if this was a really really long wire we would actually see some voltage drop and if I chuck that onto millivolts we should still see some voltage drop across there.
08:42 So, as you can see by my meter I have 0.023 volt or a 23 millivolt drop across that wire.
08:47 Not really much of an issue in our case here but this is a sort of a basic setup.
08:52 When looking at these numbers there's one sort of thing to consider and that is there are other components in our engine and our car that draw much higher current than what these lights are.
09:05 Things like a starter motor when that is cranking you are drawing quite a bit of current, so that is going to be more of an effect when it comes to grounding issues and stuff like that and I'll try and point that out later on when we're measuring things.
09:21 So, I've checked my voltage drop across that globe and as everything is working fine it'll test fine.
09:27 That's what I would expect.
09:29 Most of the voltage is dropping across that globe.
09:32 If I put my ground back to a bad ground we see it swaps over now my park light has turned on for some mysterious reason.
09:39 If I check our voltage drop across that globe now and I'm still in millivolts let's bump it back up I'm getting 0.5 volts, so we still are getting a voltage drop across there and that's because we still our current is still passing through that globe, but the problem is we've got voltage being dropped somewhere else.
09:59 So, we know we've got a good 12 volt supply 12.7 volt supply coming from our power supply or battery alternator whatever.
10:07 The next thing we want to do is have a look where that voltage drop is actually happening.
10:12 If I check across my power pin on the globe and then at the power supply power you can see we've got zero voltage drop that is a good connection and nothing bad is happening there.
10:24 However, I go from my ground and ground 12.5 volts so, that is a considerable amount of our voltage not all of it as you noticed and that's because we've still got 0.38 0.4 volts being dropped across our globe, so together that should total the same voltage that we've got from our power supply.
10:44 So, that tells us that there is actually an issue on that ground we shouldn't have any oh we should have very minimal voltage drop from the ground of our globe back to our good power supply ground or our battery ground.
10:57 So, that is probably the first and best way to test whether your ground is actually good.
11:03 Now, looking at this, so what I have here is our wire from our bad section of the switch is simply twisted around a bolt this bolt is actually painted and I think I've even got some electrical tape in there just to make sure it is a bad connection and what we can do, so this wire that I've got twisted there is on my switch yes, and the bolt is on my main power my main ground sorry, so if I actually check at this point and in your case this might be a ground lug going somewhere if I go from this point here to my ground again we've got that 12.5 volts, so that tells us that my voltage is dropping somewhere between there and essentially I could keep following this along along our wire and I probably could actually I reckon I could get just on the side of the bolt here and there we go, so between this wire bare wire and my bolt I've got 12.5 volts being dropped there is a voltage potential there, but is not actually, passing the current properly.
12:04 So, where is everything going and why is my park light on? So, the thing that's happening here because this globe is a dual filament the park and the break are sharing their ground together excuse me what we've actually got happening is the current from our indicator is actually going into the ground side because both of our grounds from these lights are connected at the same point it is going along our normal ground for the indicator passing along the ground for our globe passing through that filament back through the power wire and actually finding its way back to the power supply or the ground through that globe itself, so it's essentially running these two globes in series they're one after the other instead of parallel how they should be and because of that we're getting our uneven voltage drop our voltage drop is actually happening across this globe have a look here where's the red wire there's my 12.1 volts and then we had our 0.5 volt from that globe and then that's showing me right there that that globe is taking most of the voltage that's what we can actually see it's on this one isn't actually, on there just isn't enough voltage going through it it's all being dropped over that park light, so that's why that one's showing and that one isn't and just to reiterate i'll go back to our good light good ground sorry and there's nothing going across that globe and our full 12.7 is going across there if i flip that back we'll see that immediately drop and because of the way globe filaments work when they heat up the resistance changes we can actually see it gradually dropping down that's because things are heating up and changing, so we've through that diagnostic with a voltage drop we have effectively found that there's a problem in my wire here somewhere the ground wire where i've got a voltage potential across it, but nothing is actually passing through as i said if it is a good connection if i'll just flip it back to good we shouldn't get any considerable drop between my ground and my ground source as you can see there is still a little bit that's because of the natural resistance of that wire, but it isn't enough to drop the voltage considerably to the point where our light doesn't even work so, obviously to fix that we ground it properly or ideally ground it back to the same point as the rest of our lights, but that shows you how you know a grounding point can be quite a tricky one as you saw we still got continuity between my ground my main good ground and this grounding point here, but it actually wasn't a good ground in the end, so what are some other things that bad grounding can cause and as i mentioned earlier we can get voltage offsets for our sensors and this is where the higher current of a starter motor or other things like electrical fans come into play because what happens when we pass our current through a wire as you saw we get voltage drop across things that voltage drop can cause issues in our different grounding areas and one ground probably one thing to mention when you think of a ground doesn't necessarily mean that it is 100 zero volts it could be slightly higher than that could be 0.5 volts depending what you're referencing it to and the thing is yeah two different places in your car could actually have different levels of voltage at their ground points you could be excuse me at the back of the car have a ground that's showing maybe 0.2 voltage drop and that's just because of where it is it's a pretty decent ground then at your engine block when it's cranking it could be showing up to you know half a volt or one volt voltage drop at that ground and to give you a bit of an example here so, i've still got my good ground it's a good like this is a good setup there's no issues in this circuit, but if i go to my millivolts and i check from my ground point here good ground point from the power supply if i go to sorry i'm going to turn all my lights on just, so i got a full current my ground point at my uh what was this that was the other park light over here we can see just between that uh the ground point of the light and my ground main ground we've got 0.029 volts of voltage drop again as i said that's you know naturally the resistance of the wire it's not a problem, but the main thing i want to show you here is the difference between that ground and this one over here if i go to this one i've got 0.054, so straight up there is a difference there they're not both exactly the same, so when we're comparing grounds there we're not actually our grounds aren't at the same level and for something like a sensor sensors are using the ground that it has as a reference point and, so is our ecu, so when we have our ecu reading a sensor's voltage it's assuming that they're both reading from the same reference point or the same ground and this is why we have sensor ground outputs on our ecus or pretty much any any computer that is trying to read data directly from a sensor and that's because things like that voltage offset can cause a problem if in our situation here where our two ground points are at a different voltage level say we have our ecu connected to one and our our sensor was grounded to the other point they're both not sitting at the same reference point so they're not actually referencing the same ground or same voltage level to give a reading i think my power supply has just decided to make some noise because i'm drawing too much current i can turn that off for now, so what was i saying voltage drop sensors, so because the sensor and the earth are referencing different points that actually have different voltage levels at their ground their grounds are sitting at different points they're not actually going to be reading the same values what your sensor reads and then sends to your ecu on its sensor wire the ecu is then going to compare that to its own ground point, so hopefully that kind of makes sense and brings the point home is that your sensor is getting a voltage rating or yeah from whatever it's reading pressure levels any kind of any kind of signal that's turning into a voltage it's using its own ground as a reference point, so yeah if you've got 0.0 we'll say 0.5 volt just to make it a bit easier to comprehend 0.5 volt there it's a 12.5 volt system your sensor is going to be referencing 12 volt in itself because it has that 0.5 volt higher ground if our ecu is at a really good ground where there is no voltage drop it's sitting at zero ground and then it's getting that same 12.5 volt there is a 0.5 volt difference there between the sensor and the ecu and they're both trying to compare the same signal with a different ground and that's how we get this offset for grounding which can cause errors in our system and the problem is that error doesn't come up as a code or a you know saying that the sensor's not reading right anything like that it literally just shows a different value than what is actually being sensed at the data point so, to rectify something like that that's where star grounding comes into play and it's probably something you've heard pretty commonly especially in motorsport and professional level wiring star point grounding is essentially picking one single point in your car or system choosing that as your main grounding point and ensuring you only have one ground going to all your components and then a main ground going back to your power supply, so in my case here power supply being a power supply i would have a single point which i might call this uh the the wago wago connector that would be my star point for my grounds my main ground would go into that and then from there would star out to each of my globes individually not connected into another point and then split off because that's how we then get those different offsets by having everything going to one point everything is referencing the same point and everything reads the same, so that's why it's especially important when we're talking about ecus pdms any kind of computer when we are grounding those sorts of components we really want to ensure that we are using star grounding and that's why a lot of our engines oem especially you will see that they actually ground at the head of the engine on the engine block and not you know directly next to the ecu at the body which might be you might straight away think that is a better ground and that's because we start getting things like our voltage offsets with other components like ignition coils all those kinds of things when they start passing current especially our starter motor as i said when we start passing more current through we get a higher voltage drop we saw only millivolts here because we're only drawing three or four amps from this light setup, but when we have something like a starter motor drawing current that'll really affect our voltage drop and that's another reason why that can be sometimes confusing or misleading because the issue might only happen during a high load situation like cranking like when a thermo fan starts up when you go to high beam on your lights ac kicks in that might be the only time that you get that really big voltage offset and that might be the only time that your sensor reads wrong it might be coolant temp it might the voltage drop might send your coolant temp into a situation where your ecu thinks it's still on cold startup changes your fueling car runs terribly and we don't know what the hell's going on turns out it's a bad ground or a not not a bad ground, but a improper ground due to not star grounding that electrical system we do have the advantage with ecus where they have that sensor ground that takes away that situation where we're referencing different points basically the ecu becomes that star point ground of the sensors and the ecu itself, so that can be a little bit confusing a lot of people think you know i got star ground absolutely everything in my car the main thing to think about is star grounding the components that are essentially referencing each other or not referencing each other sorry but sending signals to each other, so a sensor sending a signal to an ecu you want to keep them on the same star ground circuit whereas our taillights nothing is happening between our taillights and our ecu, so it's perfectly fine for that to be grounded somewhere at the back of the car on say the chassis and then to the battery because that circuit isn't actually a part of our ecu circuit and that's not going to influence it at all for our star grounding, so we are thinking about star grounding and you're being told constantly to star ground star ground star ground do be aware that you know even oem they don't do it for absolutely everything it's done for particular things like an ecu that is sensitive to these signal changes and offsets, but for components that are generally maybe just like switching powers on and off door locks that type of thing windows you're not actually, going to have any issues from things like a ground offset you're still going to get a good 12 12 and a half volts 12 13 volts the only time that is going to be an issue is if you had say a bad ground like what i've got here and that's causing such a big voltage drop that it is essentially rendering everything useless or causing other issues, so when it comes to actually making a good ground one thing in particular when you bolt your ground to your say your chassis or engine block a thing to remember is it's not actually the threads from a bolt or screw that are causing are giving you your good ground connection what you really want is a nice flat surface contact between say a grounding lug ring terminal and the actual surface that has the ground so in our engine case it would be the engine block face or head face with a body ground you want to make sure it's a surface that is nice and clean as always talk about cleaning up a ground you know getting rid of paint that sort of thing primer all those things resist electricity and resist the path going through to your ground and because of that even though you might have clean screw threads or bolt threads you still aren't getting a really good connection, so making sure that you have good flat faces to bond together and create a good electrical connection that's the main thing to look, for another reason things like you know twisting wire around a bolt really isn't a good idea each of those individual strands you know not all of them are touching that bolt some of them are some of them are in the threads and not really making good contact what you're really looking for is surface area contact a larger surface area when you do have a thread you might think that you know you've got a like a triangle that you're getting more contact, but a lot of the time with those threads are only pulling onto one side and you're not actually getting that great connection what you really want is those flat surfaces that are being pulled together essentially so, that sort of gives you a good cover of how earthing can go bad some of the uh weird effects you can kind of get grounding is one of those issues where as as we saw here it can cause sort of weird signals to happen different lights to turn on common thing that you see a lot is engine grounds that have been either not put on or are missing and then you get things like dash lights coming on that are you know everything's flickering at once or maybe you've got a loose ground on your engine block or go over a bump dash lights start flickering that's sort of same situation of what we got going on here when that ground disconnects from our block all the all the components that were ground to the block are now trying to find another path and they end up finding it through your dash through the globes for things like you know like a low oil pressure light because that is actually ground through your engine block the rest of the components are using that as its grounding point sending that signal through your dash light bringing it on similar to our indicator and park light setup here, so if you're getting a symptom like that where dash lights are flickering coming on at random definitely start checking out ground points generally, i mean i sort of say ground is one of the first things that you want to check check that you got a good fuse power supply, but then definitely check that your ground point's right, but as we've seen here it's not just about having a good ground, but having your ground structure sufficient as well, so going into that we've talked about ground offsets there is another issue that you can get it commonly comes around with people sort of thinking i'm just going to chuck grounds absolutely everywhere and we'll be right as rain it's ground loops, so essentially what a ground loop is is just multiple points multiple components sorry ground to several different areas so, think of it as i've got my two lights here which are ground to this point and maybe i said okay, i got a bad ground i'm going to ground it over here as well ground it to my engine ground it to the back of my trailer whatever grounds going absolutely everywhere problem with this is we've then created a loop essentially we've created a a circuit within a circuit kind of thing as i showed you before with my ground point from here to here and here to the other section the other park light i did have a voltage difference there and when we have electricity essentially anywhere we have a voltage difference that is saying we have the potential for electricity to pass through there our current can pass through, so if we have these two points that are actually at different voltage levels different there is a voltage potential between those two points if i was to then join those two grounds up thinking i'm putting a better ground there adding more grounds what i'm actually doing is creating a circuit where there's two voltage potential differences i'm sorry a one voltage potential difference between these two points and that can actually pass current in that circuit now with things like lights and power components generally you won't see any kind of effects from that issue the things that will really be affected are sensors audio systems especially you'll often find with sound systems they tend to get a lot of noise from ground loop issues you find it a lot with the music industry because they have things like amplifiers that are connected to pedal boxes that are connected to more amplifiers than connected to a laptop you have all these different points that are actually grounding to each other and then grounding separately through their power leads and because of that they've got several ground loops everywhere and because of those ground loops you create this separate circuit that can actually it's emitting electromagnetic interference, so that circuit when we talk about loops a common thing to say when you're sort of talking about fixing interference is to keep your loops small and that's talking about these the circuit loop where if we have a ground loop we're creating a loop as I keep saying around that component between all those components and essentially anything within that loop is going to be affected by that electromagnetic interference, so minimizing that loop is going to greatly reduce the amount of interference we get and when I say to reduce that loop if we imagine here I've got a wire that joins these together for ground that's creating a loop in a circuit here by eliminating one of those grounds and just having all our grounds going to the one good source they that loop then becomes basically in between our power and ground wire there's nothing else in there's no other components in there to get affected.
29:57 Hopefully, I haven't gone into that a bit too erratically, but yeah ground loops it is in simple terms connecting a single component to multiple different grounding points because of our ground offset issues those separate ground points can cause a potential for current to pass between them creating a ground loop creating interference in other components, so ideally what we want one single ground point from a component going to sorry one single ground coming from a component going to a good ground source and start grounding with other components that are on the same similar circuit sharing information that type of thing.
30:36 You might be thinking with that things like an ECU generally have more than one ground coming out of them that's generally they have separate components inside that can be grounded differently they might all be on the same ground and that's why again it's important to ground them if you have more than one ground at your ECU ground them at the same point you wouldn't want to ground one of your ECU grounds at the head and then the other one at the back of your car there's definitely going to be voltage offset between those two points and that's going to cause issues in your ECU and you're also creating a ground loop if that ground is internally connected on the ECU because you've got your connection in the ECU that's splitting out to front and back of your car and then back to your battery and everything inside there is a ground loop.
31:29 So, grounds keep it simple one point star ground make sure any related components are going to that ground when it comes to making sure it's a good ground make sure, you've good surface connection between say a lug and your body or the engine head or surface ensure you're only using one ground, so you're not creating ground loops.
31:50 When I say one ground some components do have multiple wires, but it is still generally the same ground.
31:57 Caveat there I should touch on is ignition coils they do have two separate circuits inside of them the primary and secondary and it is really important that you the secondary side our spark side of the coil is grounded to the head basically the reason for that is we want to create that's a single circuit in itself we want to create the smallest loop as possible we want that to be confined within our engine.
32:21 A lot of coils integrate the grounds together and it's not something you really have a choice in and that's why it's generally better to ground them at the head.
32:31 There are certain situations I think like the RGN1As they have separate grounds for actually the power circuit, but the primary side and the secondary side and while it would still be okay to ground them at different points generally we'd start ground keep it at one point, but it is really important that that secondary side our the spark side is grounded to the head.
32:53 If we were to ground that say near our ECU essentially what we're happening there is through our secondary coil it's going across our spark plug into our engine it's then going to find it's got to find its way back to that coil, so because it's earthed at the ECU it needs to find a way there it's going to pass through probably engine to body ground from there it might go into the ECU ground or even through the ECU and try and get its way to that point that you've ground that coil at and because of that that's where you often get issues with things getting destroyed other components because it's got a different voltage because coil voltage is quite high if that passes through a component that it shouldn't it can destroy things, but the main thing is we're trying to reduce that loop because if it's passing through a big area we are creating interference in that area as you've heard before engines are very noisy environment cars are in a noisy environment electrically and a big culprit of that is our ignition coils and it's precisely because of that engine loop that sorry the earth loop that can be created and it is essentially there regardless between our spark plug coil and head, but by grounding our coil to our head or as close as possible we are minimizing that loop as much as possible.
34:12 I think I'm getting pretty close to the end here so we'll say start chucking your questions in because yeah I'll get to that in a second I'll just cover maybe one more thing and then hopefully you guys got some more questions and I can dive into them a bit deeper.
34:28 So, before that probably the next thing to talk about is on the the ground loop topic that's why we say to only ground your shielded cable at one end.
34:38 So, a shielded cable basically what you're doing is just protecting the wires inside by wrapping it in a good ground path that if there is a voltage being induced from an electromagnetic interference if you're wondering about how electromagnetic interference actually causes problems and noise I do have another webinar that we did a couple weeks ago that gets more into depth into that, but basically that magnetic interference is inducing a voltage into anything around it and because that can be a our wires if we wrap that in a good earth that voltage is going to go into our wire first and it's going to be dissipated throughout its own circuit not our sensor signals and the reason we want to only ground that at one end is because if we ground it at both ends we are going to create a ground loop.