Don't Be Fooled! Crankshaft Sensor vs Oscilloscope

okay so one of the members from the mechanic mindset Community had been going through our oscilloscope training and came up with uh this problem here so he posted in the community area that he'd managed to get away form up for a camshaft and crankshaft signal which is what we've got here however the crankshaft signal wasn't looking too great now this question has come up a few times in various areas and for some people it can be difficult to decide whether that is a problem with the car or it's a problem with your oscilloscope settings so we're going to check it out today so I'm connected up to this BMW b48 engine I believe and we've got a few oscilloscopes here to try out I'm currently connected up to the 2204a we are in the back of the engine control module for the crankshaft sensor and we've gone into the camshaft sensor directly here measuring on channel a and channel B Okay so we've started the engine and we're on the recommended settings of 20 milliseconds per Division and 20 volts and you can see here that we've got both signals up on the screen however we have got that same issue that Anderson was experienced where parts of the waveform are missing now I'm going to save all of the waveforms throughout this video and you can pick them up in our free YouTube waveform Library just check out the link below okay so that was the 2204a what we're going to do now is connect it up to the h8c automotive oscilloscope now this is probably one of the cheapest oscilloscopes out there which certainly will come up high on the listings when looking for automotive oscilloscopes okay so we'll double click on oscilloscope this is the default settings for this unit so we just get back to the same time settings we had there say 20 milliseconds let's just try and bring that channel two down a bit and just change the size of it there and bring channel one down and wow I think that's even worse isn't it so we're going to come back to these and see if we can improve them at all but now what we'll do is connect up the Picos scope 44 25A and see how this handles this particular test okay so this is already looking better let's just turn on channel b as well and you can see there that that is what this waveform should look like okay so no parts missing however one of the reasons that the other two oscilloscopes fall over when trying to take this measurement is this new type of crank sensor it's been out for quite a while now but the actual pull down bits are very very very small okay so you need an oscilloscope with with plenty of sample rate and memory to get it correctly which is what this oscilloscope has okay so clearly this has no problem uh taking that measurement and you should expect so it is a high-end uh Automotive spec oscilloscope however what I'm going to do is maybe show you what you could do to get a little bit more mileage out of these two oscilloscopes here so what we'll do is we'll plug this 108 the uh hch back in and we'll go with that first and after that I'll show you some little tricks that this thing has got up its sleeve to make a much better measurement we're also really pleased to announce that we now sell automotive picco scope products in the UK so if you're looking to get one then make sure you go and check out our website and get in touch and we'll help out for the most suitable kit for you okay so let's just get back to where we were let's just increase the voltage setting for both of these waveforms we'll bring the yellow one down a bit and then bring that blue one down so what you can see at this point actually is that it's picking up all of the data required now the specifications on the oscilloscope are 2.4 million samples per second that's its equivalent sample rate however the memory is only 4,000 samples so that's how many samples it can collect on one page so if we then increase that time base to where we were before 20 milliseconds you can now see that lots of data is being missed on this oscilloscope okay so that's where all the gaps are and basically if you think of the oscilloscope opening and closing its eyes to take a picture at some points it's not fast enough to actually pick the bits where that signal goes down it's clearly not good enough for this measurement okay however what we can do is maybe tweak some settings to make it a little bit better a little bit more usable okay now one of the things you need to be aware of with the sample rate and the memory is that it's split between all of the channels and in the case of this hch 1008 it's eight channels okay and if you look here all eight of those channels are switched on okay so if we start to switch these channels off it should start to get a little bit better so there's 3 4 5 arguably a little bit better okay six okay 7 and eight okay is not really made a massive difference however there are some changes to the amount of data is picked up like in these areas here however it's still struggling if we maybe turn off that last Channel there it has made it a bit better and what if we turn off all of the channels and just leave one of them going again it's a bit better but it's not great for this oscilloscope what you're going to have to do to do a proper measurement on this uh crankshaft sensor is bring that time setting down so you can see now look we've gone down to 5 milliseconds pretty much all of the data is being picked up okay so if we just stop it there you can see that there's our top dead center reference Mark however we can't get one full rotation on the screen without losing bits of information so you can see now look there's bits missing here here is not the best okay so if we just go back down to 5 milliseconds per division where we had a better measurement I wonder if we can turn on channel two and hold enough sample rate to do a timing test yeah I suppose at this point here that is good enough so what I mean by this look if we just stop it here what what you could actually do is to to check the timing of the engine you would need a known good waveform but if you stopped it here you could reference this point here to that small portion of the cam shaft there you just need to make sure that you are comparing the same parts of the waveform on your known good the big problem here look is if we go up the time scale we lose the resolution of that crankshaft sensor however you can still use it to check that the Signal's good might not be so good for checking uh you know the mechanical condition of the of the engine and things like that but I'm just going to try out of interest because this this is an 8 channel oscilloscope I'm going to put the rock key inductive pickup onto cylinder one okay and this this would be a pretty cool test if it works and we'll take a look now because we're not measuring directly onto the coil we're not going to need an attenuator with this you can see by turning on channel three that we've now lost some of that resolution again in the crank signal I'm just going to bring the trigger onto channel three okay that's what I wanted to do there actually and it's not doing the the greatest job however it is kind of working now what I'm looking at here is the the slack in the timing chain what I've doing is I've put put a trigger on that cylinder one ignition coil which is holding it there and what we're looking for really is that there's not much float between the cam shaft and the crankshaft so what you can see here actually is it's looking like it's is floating quite a lot I don't think it actually is on this car again it may be down to the oscilloscope maybe we can have another look when we plug in the um Pico scope later on but this test could be quite a good way to actually check the mechanical condition of the timing chain um slack and things like that so bit challenging there with the hch let's plug in the 2204a Pico scope and see if we can get a better waveform out of that one okay so we've connected up the 2204a now and this has only got two channels actually this third one here is a waveform generator let's see what we can do okay so even just on the 20 milliseconds per division there we've already got a better waveform okay so if we just stop that this is only on one channel remember can zoom in and what you'll notice that the main problem here is that it's not going all the way down to zero for some of those uh strikes on the sensor if you like okay so you can see as as well the the shape of these parts of the waveform they're not kind of the the correct shape they're like triangles which is the classic case of you know not enough sample rate or or memory combination of the two really okay however that is much much better already so let's just reduce that voltage make it a little bit bigger and what I'm going to do now is turn on channel B we're going to go for the same voltage 10 volts and just by turning on channel B you you saw straight away how much that affected that crankshaft sensor signal okay it's now actually a little bit difficult to determine where that TDC reference Mark is okay we just zoom in to that signal now there's lots and lots missing okay so that's down to that sample rate and memory the maximum memory on this oscilloscope is 8 kilos samples which is twice as much as the hch but again nowhere near enough to be performing measurements like this you know the picoscope automotive 250 million samples of memory that's more sample rate than that oscilloscope has alone okay so if we reduce that time base it gets better okay again it's not the best way to do these measurements but it's much better than the hand tech for your timing reference points you know you could take a measurement from you know here to here and you know maybe count the teeth that are in between those two points again just making sure that you select the same two points on your reference waveform okay so you know just simply counting those teeth is enough to get a good idea if the timing's okay of course comparing to your known good waveform however we've still not got two crankshaft Cycles we haven't got one full sweep of the cam shaft there and there is another setting on the 2204a let's just go back to this um view here 20 milliseconds per division it is also possible to increase the sample rate Okay so we've got here Target number of samples 8,000 samples which is actually about the same as the the memory depth on this scope there if we increase it is it going to make it better slightly okay so you saw there that it did get a little bit better so again it's it's not the greatest at this time base if you wanted to do that slack timing chain measurement that we just kind of tried to show with the hand Tech it may still be possible just using a lower time base so if we go to a lower time base we've got some better information there go and check out this video if you didn't already I I walk you through how to set up this measurement but what we're going to do is set an advanced trigger to the crankshaft we can see the size of it there is 3.1 milliseconds so I'm going to go to trigger going to put it on auto and change tight and we want pulse whip in fact if we just start the oscilloscope up make sure you're on channel a just going to move this up a bit if we increase this time we should see it snap there we are to that Gap and it has okay now what we're looking at is a live reading of the crankshaft being held and the cam shaft here and actually you can see there there's quite a lot of float in this chain that's more than I probably would have hoped for the measurement that we got on the hand Tech must have been correct so what you can see now look is that this cam shaft is actually kind of floating you know around about one full too compared to the crankshaft which just shows we've got a bit of slack in that timing gear there so that measurement is still possible on this oscilloscope it's quite a nice way of doing it the other thing I want to show you actually I'm going to turn the trigger off a minute because the 2204a has another little trick up its sleeve so if you are measuring here we're using the oscilloscope memory that 8 Kil samples of memory which is why this is this is pretty bad however if we go up the time base it's just going to get worse because we we're stretching that memory even further again 100 milliseconds per division really bad lots of missing information we go up to 200 Everything Changes okay so now what you can see is that it's changed to this Progressive mode okay it's what it's called here this Progressive mode and what that does then is it uses the laptop's memory so if you zoom in look we've got actually an amazing image of that crankshaft sensor okay okay well much much better anyway nice so all in all really you know if if you just want a pain-free experience when it comes to oscilloscope Diagnostics then you know go for something like this the picoscope 4425 a automotive oscilloscope however if you want to learn and kind of stretch the limits of this little thing here it is possible and and you will learn a lot okay and then when you come to buy something like this you will really appreciate what you're spending your money on

Channel: Mechanic Mindset

Views: 23,414

Keywords: mechanic mindset, picoscope, automotive, diagnostics, picoscope 2204a, picoscope automotive, oscilloscope, automotive oscilloscope, picoscope basics, picoscope training, hantek, hantek automotive oscilloscope, hantek automotive, how to, picoscope tutorial, automotive diagnostics, automotive diagnostics training, hantek 1008c, hantek 1008c tutorial, crankshaft sensor test, hantek 1008c vs picoscope 2204a

Id: uV0djQUatgQ

Length: 16min 38sec (998 seconds)

Published: Fri May 17 2024