Summary

When sensor data looks wrong, the sensor often gets the blame. But often the real problem is a ground-offset shifting the signal the ECU sees. In this webinar, we’ll explain how automotive sensors work and why grounding plays such a critical role in getting accurate data.

00:00 Hey everyone, Caleb here at High Performance Academy, welcome to another webinar.
00:04 I get a lot of questions about sensor grounding, particularly how it's best done, what can be some issues, and I see a lot of issues coming into situations of terms like ground offsets, ground loops, and also just in general when sensors go bad, but the sensor itself isn't actually an issue.
00:26 You might have a situation where you've swapped out a sensor thinking it's a problem, but you're still just getting bad data.
00:31 It's not quite right, it's not what you're expecting, or often you'll find during the similar or same situation where you'd expect the same result, you're actually getting different results from the sensor.
00:42 A lot of the time this can be ground related, it can be a ground issue, and I'll try and go through a few things in this webinar and clear some issues up for you.
00:51 Before that, this is a live webinar, if you're watching now, jump in the chat and say hello.
00:56 I've got questions after at the end of this, hold your questions until the end, I'll give you a bit of a heads up when they're going to come up just because I might naturally answer them as I go.
01:05 If you're not watching this right now or you can't watch all of it, it is recorded and it will be in the webinar archive, so you can watch it at any time, so don't stress about that.
01:14 Let's get into it.
01:15 So, the problem is we have a sensor like this pressure sensor, it's sending us a signal to our ECU, but the signal that is actually getting to the ECU isn't quite right.
01:27 And that can be an issue because our ECU is using that signal to do a number of things.
01:32 It could be using the map sensor to determine fuelage, it could be checking for just oil pressure to know that your engine is actually healthy.
01:41 So, those signals do matter a lot.
01:44 The problem then is if we have a bad signal going to our ECU, it can't make those decisions properly.
01:52 And the biggest problem is the ECU doesn't know when there's an issue outside of itself.
01:56 So, if there's a grounding issue like I'm going to talk about, the ECU doesn't know that that ground issue is there and it thinks everything's fine and it thinks the sensor signal is as it should be.
02:07 In one of my previous webinars I talked a lot about voltage drop and if you haven't watched that webinar I suggest go look at it.
02:14 It's about gauging cable sizes, determining your cable size.
02:19 I talk about voltage drop quite a bit in that.
02:21 I will talk about it a bit here because it is quite important.
02:24 I'll go over it in a bit less detail.
02:26 If you do a bit lost, maybe go watch that other webinar or chuck a question at the end.
02:31 So, basically with voltage drop, when you have a wire, you essentially have very little resistance or no resistance, but everything does have some sort of resistance.
02:42 And when current passes through resistance, you do lose a bit of energy power through that resistance because the electrons, the electrical force, has to do some sort of work to get through that resistance.
02:55 That ends up being dispersed as heat, might be light if it's in a light bulb, something like that.
03:01 But the fact is a wire has resistance and if you have too long of a wire, like I talk about in the wire selection webinar, if your wire is too long, you can have too much voltage drop and because there is too much resistance in that total length and that causes big issues.
03:17 So, why does that come into play with sensors? It's because a lot of sensors use voltage drop as a way of measuring.
03:25 I'll go into that a bit deeper, but just to get your head around it, I'll give you a bit of a demonstration now of how voltage drop actually works, especially with wiring.
03:35 So, I've got a nice long roll of wire here.
03:37 If we go to our overview, head overview, what do we call it, overhead camera, and we have a look at my little setup that I've got going on here.
03:44 I've got a light bulb under this piece of paper.
03:47 You don't need to be blinded by the light, so I've just covered it.
03:50 We've also got just a 12 volt power supply and a simple multimeter.
03:55 Basically, it is purely set up at the moment, 12 volt into the light bulb, earth back to the power supply.
04:00 It turns on as it should.
04:02 All is happy.
04:03 If we grab our multimeter, and I'll turn it on, so you can actually get something out of this, we will see quite simply across these two points, we will have, I think it's about 13.8.
04:18 Hopefully, you can see that.
04:20 I've got the backlight on.
04:21 There we go.
04:26 13.79, I was close.
04:28 So, that is basically what this, yeah, it's exactly what this power supply is outputting.
04:32 There is no voltage drop at that light bulb.
04:35 So, let's introduce a situation where the wire actually goes quite a distance.
04:40 And I've got this big roll of wire here.
04:42 I've managed to get one end of it in the center here, which we're going to attach our earth to.
04:46 And then the other, I put another clip lead to, and we're going to connect that to a light bulb.
04:51 And this is basically simulating this, I mean, I don't know how many meters of wire I got here, but a very long wire.
04:58 And with every foot or meter of wire, you are going to add resistance because it all has that little tiny bit of resistance.
05:05 Now, when I turn on the power supply, it still lights up, everything's still great.
05:09 So, you might think, hey, what's the problem? Problem then arises if I check the voltage across this light bulb.
05:17 If we have a look at our multimeter there, I'm down to almost down to 11 volts.
05:23 So, we've got quite a drop there of voltage drop.
05:27 And the best way to actually measure what that voltage drop is, we can measure between the two points.
05:33 So, between our two earth points from the power supply itself and the other side of our wire here, and our multimeter, sorry, from the power.
05:43 What am I doing here? So, I got the wrong one.
05:45 I've gone to the same point, that's why.
05:47 The other side of our wire, sorry, at the light bulb.
05:50 So, that is showing our voltage drop across that ground wire, and there's a whole 2.6 volts.
05:54 Now, this is an extreme situation.
05:56 You're obviously not going to have a massive coil of wire that can actually heat up quite a bit if it's not appropriately sized.
06:02 I think my paper's actually about to burn, so I'll turn that off.
06:05 But as you can see there, by having too much wire, there's too much resistance and we actually, get a drop in voltage.
06:10 Now, with the light, as you saw, it wasn't a major issue.
06:12 The light is still bright.
06:14 You can still be able to see in the dark.
06:16 But if that was something like a fuel pump or something that needs a critical voltage level, it's going to cause some issues.
06:24 Fuel pump might not be supplying the right amount of fuel.
06:28 Or if in the case of a sensor, that sensor might not be sending the correct reading.
06:32 So, that is essentially why good grounds and voltage drop is such a big issue in things like sensors and signals.
06:39 But having said that, sensors actually use voltage drop to create that signal.
06:45 So, I'll explain that now, because that might have just sent everyone over the edge.
06:50 But if we go to our top down again, I've got my little section here where I am drawing.
06:55 We don't need any of this anymore, so I'll move it out of the way.
06:57 This is a voltage divider.
07:00 You may have heard about those sorts of things or seen it drawn in schematics somewhere.
07:05 It can look a bit complicated if you've never seen schematics before.
07:08 Basically, what I've got here, we've got a 12 volt power supply.
07:12 So, just any old car battery or like I've got here, a benchtop power supply, simple wire in a loop.
07:18 So, we've got a circuit and two resistors, resistor one, resistor two.
07:23 Each of these are 1000 ohms.
07:25 So, each of these have resistance of 1000 ohms.
07:28 Now, we're going to pretend that these wires connecting are perfect conductors.
07:33 They have no resistance.
07:35 They're not going to come into play in the real world.
07:36 Like we saw, wire does play a major role in this.
07:40 To explain this, though, we're only going to reference these two resistances.
07:44 So, a voltage divider is basically a good way of dropping voltage at when you want to say having 12 volt going into an ECU and the ECU can only accept 5 volt signals from a sensor or something like that.
07:58 A lot of electronics work on 5 volt or less, and that's why it's often used.
08:03 Things like ECUs, you'll have a 5 volt out to your sensor.
08:06 So, what's going on is these two resistors are creating a voltage drop.
08:11 As I showed before, imagine one of these is our roller wire.
08:15 And as I showed you before, measuring from the ground to the other side of that resistance, you can see what that voltage drop is.
08:26 And, so your ECU is actually using this as a way to measure a signal.
08:31 And the way it does that, we've got a nice big formula here.
08:35 Basically, we'll break this down a little bit.
08:37 Voltage out, that is the voltage between here.
08:40 That's where our signal is.
08:41 So, V out or it'd be your signal.
08:46 So, that's our point that we want to actually know what it is.
08:50 That's going to be our signal.
08:52 What we do is simply Vs, that is our voltage supply, which is over here, 12 volt times by our R2, resistor 2.
09:01 I've chosen pretty simple numbers here just to make it a bit easier.
09:05 In the real world, these would be all over the place.
09:08 But we're going to have on our top here, 12 times by 1000, 12, 000 divided by R1 plus R2.
09:17 So, our resistance added together, which is simply 2000.
09:20 And we divide that and we get 6.
09:23 So, our output at this point here is 6 volt.
09:26 And if we had a situation where I had that all wired up, you'd get your multimeter and going referencing from our ground to that point, you would see 6 volt at this point.
09:35 12 volt on that side, 6 volt here and 0 here.
09:39 It's dividing the voltage between those resistors.
09:42 So, how does a sensor use this? Well, commonly a lot of old sensors, things like temperature sensors, old pressure sensors, your single wire sensors that you often see for things like gauges.
09:54 They're this sort of situation here.
09:56 Imagine this is a temperature sensor in your engine.
09:59 They're essentially a resistor.
10:01 That is how they are creating their signal.
10:03 They imagine they're in this R2 position inside the way that they work.
10:09 They have certain materials that expand or contract at certain rates or react to what they're measuring in a certain way.
10:18 So, a temperature sensor, when it gets hotter or colder, its resistance gets higher or lower.
10:23 So, we use that as our resistance in R2 here.
10:26 We can basically wire that up to our ECU.
10:29 And when we apply a voltage here and change that resistance, we get a different signal.
10:35 Now, there are some things that happen inside your ECU.
10:39 You have the other R1 resistor, the voltage in.
10:44 And that's when you, if you're setting up an ECU, you'll often see or hear things referred to a pull up or pull down resistor.
10:50 So, when you are wiring up a temperature sensor, you'll be told to set up a pull up resistor.
10:57 And basically what you're doing is connecting this pull up resistor to your circuit.
11:01 So, this wire here is actually coming in to this point here.
11:05 Sorry, no.
11:08 Thought I had a permanent texture there for a second.
11:10 It is, where are we? Well, essentially it is.
11:13 Sorry, this is a bit of a hard thing to draw.
11:15 That's just, I'll draw a box around here.
11:16 That's our temperature sensor.
11:19 So, that wire there is coming into our ECU.
11:22 It's then grounding this situation.
11:24 It is grounding through our block, which then eventually goes to our battery and where our ECU grounds and everything.
11:30 On the other side of our temp sensor, we have inside the ECU, which we imagine is basically all this, our pull up resistor and then our voltage out.
11:40 So, it's referencing this.
11:42 It's saying, OK, this resistor is at a thousand ohms.
11:46 We've got a known voltage on the other side.
11:48 It's now showing six volt.
11:50 In an actual sensor case these days with five volt sensors, it would be under the five volt because it'd be supplying five volt to this supply on this side.
11:58 But what you just need to understand is that it's using this setup to actually determine a voltage that it can then reference that to, say, a certain amount of temperature, a certain amount of pressure.
12:10 So, a big thing here to remember is voltage is just a reference.
12:14 It's you're referencing two points.
12:16 So, ground and then another point you can reference either side of this resistance or that side of resistance.
12:22 And it's just telling you the potential voltage on one side and the other and what can move between that.
12:28 Because a battery, when you read, put a multimeter across here and you see 12 volt, you're seeing the potential for 12 volt.
12:35 If everything's disconnected, you'll see that you're getting 12 volt on that side because inside it basically wants to push electrons around 12 volt worth.
12:44 I go into this a lot better in the other webinar.
12:47 I don't want to go too deep into it now.
12:49 If you have any questions about it, leave them to the end and I'll try and clarify them a bit further.
12:53 Now, more modern sensors like the one that I've got here, which is a three wire, they have some electronics inside that do their own, what do you call it, do their own signal generation where they have their own five volt and their own ground.
13:11 So, they take the engine block as a ground out of the situation.
13:15 And this is particularly to help with things like ground offset, which I'll explain in a minute.
13:20 So, the reason we get such an issue with having our ground at different points is, can you imagine if the one of our wires here, say this is the ground point and it goes through the engine block and then has more resistance because there's a bad ground there or something.
13:35 That can then mess around with the voltage that the ECU sees because the ECU is always referencing its own ground.
13:41 That's a big thing to think about.
13:44 The ground at the ECU inside, if you imagine it's using a multimeter to check the signal, it's using its own internal ground as a reference point.
13:54 And if your sensor here is, if you then connect that to your engine block, your sensor itself is then using that engine block as a ground.
14:01 And I've got a demonstration I'll show you on the computer in a minute that will actually show you why this situation can be bad.
14:07 And this is where you get things like ground offset.
14:10 I'll just take a quick drink.
14:12 I just want to go over my notes quickly.
14:15 So, a common, a lot of sensors are built this way.
14:19 They vary resistance to create a certain voltage or resistance itself.
14:25 There are sensors that work in a bit of different way.
14:27 We're going to keep it just to this as a good example.
14:30 Common sensors are like your coolant temp sensor, air temp, fuel level, your arms that move up and down.
14:36 They're moving along a resistor strip and adjusting the amount of resistance as it moves.
14:42 So, it's doing exactly the same thing on your dash.
14:44 Your gauge is doing this voltage divider setup that will then move the needle in a certain way.
14:50 Much older gauges will actually have a piece of metal that bends in a certain way at a certain voltage and that's how it moves the needle.
14:57 But I don't want to digress.
14:59 So, with the three-wire sensors, because we have that opportunity to move our ground and have a continuous regulated power supply, it does make them more reliable.
15:11 That's one of the main reasons that we have 5V out and sensor out on our ECUs.
15:17 So, we can use them dedicated for our sensors.
15:19 Because at that point we have a dedicated reference.
15:22 We're not grabbing 5V or power or ground from any other place in our circuit.
15:28 Excuse me.
15:28 We are getting it from our ECU and a good reference point.
15:32 The point where the ECU is referencing.
15:35 And the problem here is when you start having a bad ground setup, your ECU has no idea that's happening.
15:43 It's still taking this input and going, hey, this is my signal.
15:46 I'm just going to do with it what I can.
15:48 I don't know what's actually happening elsewhere.
15:54 All right.
15:55 So, let's get into ground offset now.
15:57 I'll explain that a bit further.
15:59 Because it will lead into ground loop as well.
16:02 So, hang in there.
16:02 But for ground offset, if we have a look at my computer screen now, I've got a good website.
16:09 It's called Tinkercad.
16:10 If you haven't seen it before, it's run by Autodesk.
16:13 It's just a good place to play around with electronics and see what they do.
16:17 It's really good for setting up micro electronics, not really automotive stuff.
16:22 But for this sort of setup, I really just want to show how the voltage works.
16:26 I want to give you an actual visual of this kind of thing happening.
16:30 Because saying it and just giving numbers and stuff doesn't really sink in sometimes.
16:35 So, hopefully this will make it a little bit more obvious.
16:39 I don't have things like an engine block or an ECU on this program.
16:42 So, you have to bear with me as far as a bit of imagination.
16:44 But if we have a look at what I've got here, we've basically got our two main circuits.
16:50 Power supply over here, which we imagine is our battery.
16:53 That's going to be supplying our 14 volt.
16:55 That goes along some wires to our ECU at the top here.
17:00 And our engine block at the bottom here.
17:02 We have a starter motor connected to our engine block, which is going to be just this little switch down here.
17:07 I have resistors set up in this circuit, basically, to simulate high load from the starter motor and also resistance in wires.
17:16 It's going to be a key part of that whole voltage drop situation.
17:20 And then in the center here, I have a sensor.
17:24 If you've ever seen microelectronics, things like potentiometers, they are literally just a resistance band that you turn and it varies the resistance.
17:33 Essentially the same thing as what a sensor is doing.
17:36 It's altering the resistance and changing that circuit.
17:39 So, I've got a potentiometer here as a simulator for a sensor.
17:44 All of these little multimeter sections around are going to show us voltage at different points.
17:48 As I said, voltage is just a reference.
17:52 These multimeters are referencing different points.
17:55 So, to explain that a bit more, we've got down the bottom here, a multimeter that's going to be referencing our starter motor power.
18:02 So, the voltage that that starter motor will be seeing.
18:06 At the top here, it'd be similar.
18:07 That's what the ECU will be seeing.
18:10 One over here, that'll be measuring the actual sensor.
18:14 So, what the sensor itself is reading.
18:16 And then at the top here, it'll be as if the ECU is doing its reading.
18:20 So, we can see here, my earth is connected to the same point as the ECU because the ECU references its own ground.
18:27 And I should be able to start this up now.
18:30 And that should show you now clearly 14 volt at our starter.
18:35 I'll just say the starter motor is not on at the moment.
18:37 So, there's no current load.
18:38 This is just measuring the voltage potential there.
18:42 14 volt.
18:43 ECU has 14 volt.
18:44 It's going through a 5 volt regulator, which is usually what's going on inside the ECU.
18:49 And that's then our 5 volt out, which goes to our sensor.
18:53 The sensor has an orange wire here, which is our signal wire back to our ECU, which is at the moment currently reading 2.5 volt.
19:01 And we can see as the multimeter at the sensor itself, that's also reading 2.5.
19:06 So, in this situation, everything is all good.
19:08 In the middle here, I've got a switch.
19:11 And basically what that's going to do is going to swap from our ground offset, bad grounding situation to a good grounding situation.
19:19 The ground comes from the sensor to the center of the switch.
19:22 And at the moment with the switch on this side, I'll just zoom in a bit, make it a bit obvious.
19:26 With the switch over to this side, it's grounding to the ECU.
19:30 If I was to flick that switch, the ground would then go down here and be from the block and the same point as the starter motor.
19:38 So, if I flick that over now, you'll see it did nothing.
19:41 It hasn't affected anything at all.
19:43 And that is why grounding issues can often be tricky to diagnose because a lot of the time it won't cause an issue.
19:50 It might be very intermittent.
19:51 When I said before about sensors giving bad data, you might have a situation where it's looking good most of the time.
19:59 And then at some random moment, the voltage or the signal tweaks and goes out of whack and nothing has actually changed.
20:07 Say if it's for a pressure sensor or a TPS, the actual reading hasn't changed and it shouldn't have changed, but it has.
20:14 And that is because we have, as I said, voltage drop.
20:18 When a current passes through a wire or a resistance, it creates voltage drop.
20:24 And that's why I've got the starter motor here.
20:26 The starter motor is going to create a very high voltage, sorry, a very high current through this earth.
20:32 And that is the same point that our sensor is earthed to.
20:34 So, as you can imagine, that's going to cause an issue because the high current from that starter is actually going to cause a voltage drop.
20:41 And when we cause a voltage drop, we're going to have not the same reference point.
20:47 So, if I turn that starter motor on now, we see that drops down to 13.5 volts at our starter.
20:52 So, we've got a whole half a volt drop to the starter motor.
20:54 Normally, this wouldn't be an issue.
20:57 If you've told to test a starter motor, generally it's nine to 10 volts.
21:02 A voltage drop is still fine.
21:04 That's just expected from a starter motor.
21:07 I'm using pretty exaggerated loads here, but things like your injectors, coils, fuel pumps, fans, all these things can cause some voltage drop and can cause similar issues to this.
21:18 Maybe not as exaggerated, but it can still cause an issue.
21:24 You can see that my voltage at my sensor, what the reading is, has actually dropped as well.
21:28 You can see when I turn that on and off, it drops that voltage.
21:31 Now, that wouldn't be a major issue if we are referencing the same point and we know that that's sort of happening.
21:38 But the fact is, if we come back up here and look at our ECU, that's still at 14 volts and we can see that it's reading 2.75 volts.
21:46 We can see there we've got our half a volt difference and that's because our ECU is still using its good ground that it's got up here that has no major current going through it and no major voltage drop.
21:56 It's still seeing 14 volts.
21:58 The sensor is referencing our engine block, which has a voltage drop, so they're not the same.
22:05 And, so at the end of the day, we're not going to have the same reading.
22:08 The 2.75 at the ECU sensor is actually reading 2 .25.
22:14 As I said, it's exaggerated, but just that small amount of volts, millivolts, can cause big issues.
22:20 This sensor that I have here, it's a 0 to 10 bar pressure sensor.
22:27 Most three-wire sensors that are 5 volt, the signal itself will be reading 0.5 to 4.5 volt, so, it doesn't use that full 5 volt range.
22:38 But basically, you've only got those 4 volts in between to actually measure a signal.
22:43 For 10 bar, you're looking at up to 145 psi.
22:48 That has to be referenced as for the signal of 4 volts.
22:53 So, every little millivolt jump is going to change that quite significantly.
22:58 And 145 or 10 bar pressure sensor, just for half a volt, as we're seeing on this setup here, that's up to 18 psi.
23:06 So, if we're measuring our MAP sensor, if that's our MAP sensor that's being affected, that's 18 psi difference that your ECU is seeing, and it's not actually what's going on.
23:16 And especially for things like a TPS that's measuring position, that half a volt could mean the difference between your ECU seeing...
23:24 If I turn this potentiometer, it'll actually change that dial.
23:29 Say our ECU knows 4.5 volt as throttle 100% open.
23:34 So, we move that up to our 4.5.
23:36 The ECU goes, cool, we're at full open 100%.
23:39 I'm not going to drive the motor anymore, the throttle body motor.
23:44 But at the actual sensor itself, it's reading 4 volt.
23:47 Its position is only maybe 90%, 95%.
23:49 You're not actually at full throttle.
23:51 So, this is where things cause issues, but there is no faulty product.
23:57 You don't have a faulty TPS.
23:59 You don't have a faulty ECU.
24:00 What you've actually got is a ground offset.
24:03 And we can see here the voltage difference in the center here.
24:05 This is our ground offset.
24:07 This is measuring the potential difference between these two grounding points, the engine block and the ECU itself.
24:14 And what that's saying is this engine block is actually 500 millivolts, 0.5 volt difference than this one here.
24:26 Big thing to understand is just because you have ground doesn't mean it's electrically zero volt.
24:33 It can be just above that.
24:35 As I showed you with our setup here, the wire, we'll still measure that and see a ground on one side of that globe.
24:44 But if we were to connect another device into it, that wouldn't truly be zero volt.
24:48 In that situation, we had 2.5 volts.
24:51 So, we might think, yep, that's the earth side of the globe.
24:54 It's connected to earth on the battery.
24:56 That big voltage, the voltage drop from our wire is actually meaning that that ground isn't a true ground.
25:02 And that's for something like a globe, not a huge issue.
25:05 But when you've got sensors where every millivolt counts for your signal, that can cause major issues.
25:11 And that's why our ECUs have an internal sensor ground output and a 5 volt output.
25:18 Everything, so that the ECU knows the reference points.
25:21 It's using those known points inside that aren't being altered by high current from the starter or any other actuator, that sort of thing.
25:29 And in saying that as well, things like your injectors and igniters for coils and things, it is good to try and wire them away from everything else as far as power supplies and grounds.
25:44 That's what we generally have, especially with our coils.
25:46 They're grounded straight to the head so, that the current only passes through there.
25:50 It's when you get in a situation like this that I've got on the screen where you're grounding to several different points.
25:56 So, imagine our battery is over this side.
25:59 That's our main ground.
26:00 And we've got that now split to two different points.
26:03 And then from those two different points, we're grounding other components.
26:07 So, when people talk about star point grounding, that's sort of what we're trying to avoid.
26:12 We don't want lots of grounds going to one point from a component, from lots of components, from there going to another point and then converging into one.
26:22 Because we get this situation where different resistances cause different voltage points or voltage potentials at these ground points and things that are referencing that, like an ECU, it just causes these big issues.
26:38 So, you might be thinking then, if we were to join these two Earths together, that would make them both the same Earth and they'd both be referencing the same point.
26:47 This is where a ground loop comes into play.
26:50 Basically, a ground loop, a lot of people say only run one ground, don't ground your components at multiple points.
26:59 And that is true, but it also depends on the situation.
27:04 Some things, like a globe, if you're grounding at different points, it's not going to have a huge effect.
27:09 As we saw, the voltage drop didn't really affect the globe that much.
27:12 But when those grounds are being used for important things like sensors, ECUs that are referencing those grounds, just things that are sensitive to those voltage differences, that's when we get big issues.
27:25 Because a ground loop can actually, if you think about, as I've said here, we've got 0.5 volt difference.
27:33 And when we have a difference in voltage, that's when current can flow.
27:37 That's the whole theory behind a battery.
27:40 You've got a voltage difference on both sides.
27:42 We join both sides together and we get current flow.
27:46 So, by joining a wire between these two points and earthing them together, we've got a ground loop.
27:53 There is a loop here where the things like the starter motor load, even our ECU load, if there's injectors and things being driven there, it has multiple paths for that current.
28:03 When we start that starter load, it's going to be going back to the battery on its main power wire, but it's also going to be sending current on the other wire and causing voltage drops and noise and things on that wire.
28:15 And that's the biggest thing with ground loops.
28:16 They introduce things like noise quite badly.
28:20 And that's why we want to avoid that.
28:22 So, in theory, what you want to do is, as I said, the star grounding method, which is choosing one point where your grounds go to.
28:32 So, in a motorsport situation, we generally use an engine head as a good ground point.
28:38 It's one single point.
28:39 Battery comes to there for its main ground.
28:42 Everything else then grounds to there.
28:44 That then avoids our situation where we have a difference in ground potential or voltage potential at different points.
28:52 A lot of the time, OEM, we use the chassis of a car.
28:56 Because the chassis itself is just one big conductor and it is good as a ground, you generally won't have a situation where if you've got grounded to your chassis rail and then at the back of your car with your battery, if it's a good ground, there won't be any voltage drop because there is very little resistance for such low voltage and current.
29:14 But you can have situations where if you chuck a ground on somewhere in your car that's actually a little bit rusty, if you've got an old Civic, and that's when you start having issues where there's more resistance in just that one part.
29:28 And then you've got a ground in another part of your car and that's a nice clean ground.
29:32 You've actually got a voltage potential difference between those two points and that's where you can run into these kinds of issues.
29:38 So grounding, using your chassis as a start point ground isn't a bad thing.
29:42 It's just, you need to be very sure that what you've got there is a good ground, no paint, nice and clean, good electrical contact.
29:49 Be careful of things like panels that are just spot welded, they might be spot welded by very tiny spot welds that don't actually give good conductivity between the two panels.
30:00 So yeah, that's one of the reasons why we want to avoid a ground loop, is we don't want to just, sorry, we don't want to just want to chuck a heap of grounds onto every which place and say, yep, cool, we've got grounds everywhere.
30:11 It's one of the reasons I hate seeing, you see from JDM cars come in a lot.
30:14 One of my mates bought a Lancer Evo 6 from Japan and it had a grounding kit on it and it was just a big ground bar on the engine and had grounds going absolutely everywhere and joining things together and multiple, yeah, just grounding at multiple points and that can become dangerous because yeah, you've got all these different ground points that can be at different resistances and things like that and it's just not actually a good thing.
30:40 One good ground is going to give you better results than trying to have a whole heap of little grounds that could potentially be different and might not be as good.
30:50 Having said that though, if you do have a component and you do run two grounds for it to the same point, you are going to have a better ground, but it's why do that when you can just run one wire, situations like that.
31:00 There are caveats to the saying what I'm saying.
31:04 Basically though, at the end of this, what I want you to get is voltage drop is a big issue.
31:10 It's an issue, but it's also a key ingredient on how things like ECUs and sensors read data from our sensors and things like that, but can cause problems with, when I showed you our wire with too much resistance and even just things like your grounding points, which is the main thing I want to take away from this is good grounds give good data and when it comes to an ECU, ECUs are pretty damn smart these days.
31:38 They're great bits of technology, but you get what you put in.
31:42 You get out what you put in.
31:44 If you put garbage in, garbage results, garbage signals, that's what you're going to get out.
31:50 We're going to be getting to the end here now, so, if you've got some questions, chuck them in the chat and we'll get them in there for me to hopefully answer by the end of this.
31:58 In the meantime, what have I got here? Real motorsport examples.
32:04 This creates issues for us in motorsport, especially if things like CAN bus, your grounding points between components, if they have a major difference, you can start introducing noise.
32:15 Ground loops.
32:17 A big one where you see ground loops are an issue and the whole reason we say not to ground your shielding cables in both sides.
32:28 So, with audio is a good example of this.
32:30 You see RCA cables and things, they come with a shielding wire that comes in it and you can ground that on either end if you want to, but when people do that, what they're actually doing is creating one of these ground loops.
32:42 So your, say, amplifier and your head unit both have their own main grounds, but then this signal wire that's going between the two has a shielding around it and is now grounding those two components together.
32:53 That's creating your ground loop.
32:54 So, it's a loop where you might have two differences in voltage potential on either side at the ground point and that signal is getting distorted and noise because a current is actually passing around that circuit.
33:08 And that's one of the main things that ground loops can affect.
33:12 So, you see ground loops creating problems a lot with audio equipment in motorsport cars, but also in even just our situations with sensors that have shielding wire.
33:22 That's the main reason you don't ground your shielding wire at both ends because you will create a ground loop.
33:30 And yeah, just going over this, the biggest thing why it's such a problem is because your ECU is referencing these different voltages and the main thing I want you to take away from it is the voltage that it's seeing is a reference and it references itself.
33:46 So, think about it as, I had a good example of this before, we'll go over to the top down and imagine you're trying to measure the height of a mountain.
33:56 So, you've got a mountain, we're in New Zealand, so, it's going to have snow on top.
34:00 And you're going to measure that in reference to sea level and imagine that your sea level continuously changes.
34:08 This is our reference point that the ECU is using, which should be zero volt.
34:12 And up here is our 4.5 volt.
34:15 We want to measure that distance.
34:17 But when we have ground offsets or ground loops causing issues, this ground reference point is actually going up and down.
34:23 And you can imagine how frustrating that would be when you want to measure the height of a mountain.
34:27 You're constantly getting this moving target at the bottom and your readings actually don't match up with how big the mountain really is.
34:34 Hopefully, that's a good demonstration.
34:38 Again, I'm coming up to the questions in a minute, so, make sure you get them in there.
34:40 I'm just gonna have a quick look, make sure I haven't skipped over anything important.
34:55 Now, I think I've covered everything.
34:56 Hopefully, I'm sure you'll chuck some questions in.
35:00 Yep, I've gone over all my notes.
35:02 I have a bad habit of skipping over my own notes.
35:05 So, hopefully that gets into it.
35:07 If not, like I said, questions in and I'll get into them right now.
35:11 We've got DreadQ.
35:13 I have an aluminium chassis.
35:15 How should I deal with grounding? Aluminium is actually a good conductor.
35:20 The biggest problem we see is a lot of aluminium components are...
35:27 Sorry, what do you call it? Anodized or powder coated.
35:29 It's those coatings that really cause issues with aluminium.
35:32 Aluminium is still a good conductor though.
35:34 It's something I've heard in the past.
35:36 You can't ground to an aluminium chassis or to an aluminium component because it's a bad ground.
35:42 But it is a good conductor.
35:45 It's metal.
35:47 It's not as good as other components, other things like copper and things like that.
35:50 But we do have aluminium core wire in some situations.
35:54 So, the biggest thing to deal with, the biggest thing to remember when you've got an aluminium chassis is things like your coatings.
36:02 At the end of the day, you don't treat it any different to any other chassis.
36:07 When you've got a steel chassis that's painted, you obviously want to get rid of that paint.
36:11 You want to get rid of anything that's not conducting electricity.
36:13 You want to have a nice metal to metal contact point and it allows those electrons to flow nicely.
36:20 Moving on, we got boost inefficient.
36:26 Just up the boost a bit.
36:28 So, if you add a ground loop in TinkerCAD, will you see a difference in ECU sensor voltage versus actual sensor voltage? I haven't actually tried this in the TinkerCAD.
36:39 Will we see a difference in the ECU sensor voltage? No, we won't see a difference in those two voltage points because we are joining that reference point and the ECU is using the same ground point.
36:53 The ground loop isn't, so much causing issues in that point of the ECU seeing different readings.
37:01 The ground loop is causing issues with current passing through the same circuit and causing things like noise.
37:07 So, in this situation, it won't actually, it'll solve our problem if I join these two together.
37:15 It will get rid of that voltage drop because we're joining those two points together.
37:20 So yeah, that's why I wanted to sort of go over that.
37:23 It's not a fix because you're actually introducing a whole new problem.
37:26 It's still a ground problem, but it is a different problem in itself.
37:28 This will cause a lot of noise and interruption This will cause a situation where that sensor reading will start to fluctuate and get readings that aren't right.
37:38 Sorry, the ECU will see that same sensor reading, but it will be wrong because it's got noise interrupting it and things like that.
37:45 Hopefully, that's not too confusing.
37:48 What have we got next? Innerspace56, I never could have imagined how important sensor wire shielding could be until I landed a cam sensor wire shielded chassis.
37:59 This is enough of an error to cause the engine to cut out in traffic.
38:03 Yeah, 100%, like that is the thing.
38:06 You don't often know it's going to be a problem.
38:09 You often think, you know, if it's grounded, it's good, it's better.
38:13 But you get situations like this where that little bit of just grounding the shield has caused a big sensor issue and the signal error.
38:23 Of course, something like a position sensor, cam sensor, they're very sensitive signals and that's why we use shielding for them all the time.
38:31 So yeah, just having that small bit of interference going through your shielding, being grounded at both points is going to cause big issues.
38:39 And I'm just getting notes now.
38:41 This is an update to that top same comment.
38:45 The interference would cause my cam signal to slam high five volt and the ECU responded by hitting the rev limiter, cutting the engine off momentarily.
38:53 This would usually happen at traffic lights.
38:55 Yeah, so that's not ideal.
38:56 So, that is a very good example of why these good grounding situations, avoiding things like grounding, shielding at the wrong place, it is key.
39:03 It does cause quite significant issues if you haven't found those issues at testing point.
39:09 A lot of the time we hopefully find these issues when we're just testing a car on a dyno, that kind of thing.
39:13 But also it can, like it's happened to in a Space 56 in the middle of traffic, which is not ideal.
39:19 It looks like we haven't got many more questions, no, more questions.
39:22 So, hopefully that means this has made sense and covered things in a way that you can understand.
39:30 If you have any more questions, if your question didn't quite get in here, jump on the forums.
39:34 We are always checking that and trying to answer questions there.
39:38 If you're watching this at a later date, if you haven't joined us live today, same thing, jump on the forums, ask some more questions.
39:44 More than happy to try and answer them for you.
39:47 Sorry, my page is being changed here.
39:49 I'm just hoping it's another question.
39:50 I think we're all good.
39:51 But yeah, that is a voltage drop and why it is, so critical with things like grounding and sensors.
39:58 And hopefully this gives you a bit more idea of why ground is, so important, why we use those sensor grounds from your ECU only for your sensors, not for other things.
40:06 Don't go powering your undercar LEDs with that ground.
40:09 It's gonna interfere with the sensor signals.
40:13 It is important.
40:14 We're not just saying it for the sake of saying it.
40:17 Please remember your grounds.
40:19 They are just as important as your power supplier.
40:23 That's all I've really got for you today.
40:25 I hope you've enjoyed it.
40:26 I hope you join us for more webinars and see you around.