Sensor, wiring or ring ?? (Digital)

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Sensor, wiring or ring ?? (Digital)

Postby RYM6746 » Thu Apr 27, 2017 2:51 pm

Hi All I have a 2010 hyundai i10. ABS light intermittently on and ABS randomly goes off when foot is on brake at low speeds. So you would think broken ring right? visual inspection says otherwise no breaks no cracks and air gap is consistent when wheel is turned. Whip out the pico adding a maths channel and this is what i found. I can't see a missing or cracked tooth in the waveform but the maths channel is showing some normal wheel speeds and then dropouts (No consistent drop outs like with a missing tooth). The last 10 sec is only where the ABS module saw a problem and logged a fault (capture8). I'm thinking its a sensor problem due to the intermittent fluctuations in voltage (internal resistance changing). This waveform is taken at the ABS module using sensor ground. what are your thoughts? I'am certainly not an expert on digital ABS sensors!
Am I using the maths channel correctly?
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Hyundai_i10_2010_Petrol_dropping out 2 forum.psdata
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Re: Sensor, wiring or ring ?? (Digital)

Postby Technician » Thu Apr 27, 2017 8:49 pm

Something very very wrong there. Here is a typical sensor pattern you should be seeing;

https://www.picoauto.com/library/automo ... r-digital/
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Re: Sensor, wiring or ring ?? (Digital)

Postby RYM6746 » Thu Apr 27, 2017 9:39 pm

The typical sensor pattern is the blue trace zoomed out? It is a square waveform when you zoom in on it. The maths channel should (if I have done it correctly?)represent the wheel speed, I am road testing vehicle with a long time base due to the fault being intermittent. The very last capture showing movement of roughly ten seconds with lots of drop outs is where the computer logged a fault code saying wheel speed front right incorrect signal. I was monitoring the scan tool at the time on live data and at that moment in time I saw the offside front drop to practically nothing with a few upward glitches in it. At that point I flicked back to the scope and stopped it. The long pause before and the capture before is just me stopped at a junction where no wheel speed is present. There are captures of the maths channel shows nice smooth linear wheel speed as you would expect. Right at the start of the road test there is also lots of what looks to drop outs in signal on the maths channel - but the blue trace is always there pumping out a square waveform signal? Occasionally the voltage on the blue trace seems to go out of the normal operating area? These are all variables I was not expecting to see and I can only make sense of about half of what I have captured that is why I have put it on here for some help.
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Re: Sensor, wiring or ring ?? (Digital)

Postby STC » Thu Apr 27, 2017 11:24 pm

RYM

Looks like you have a GMR / AMR Speed Sensor there, very clever how the get the signal to discretely ride on the supply wire. Hence not the easiest things to scope.

I can confirm that your capture appears, at first glance to be Very Very Right !

Inferior scope users wouldn't have a hope :D

RYM, at times like this when there is uncertainty over a waveform we need a Known Good.

Please take another capture, with less time across the screen, high sample rate of the suspect sensor and also the other good wheel on the same axle. Please add Amp Clamps to both wires too - that is 4 channels populated.


I can't see a missing or cracked tooth in the waveform


Does this have a reluctor wheel with teeth ?? Or Magnets embedded in a bearing ???
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Re: Sensor, wiring or ring ?? (Digital)

Postby RYM6746 » Fri Apr 28, 2017 12:40 am

It has a reluctor ring on the drive shaft. I shall try my best to get a waveform from the other front wheel along with with the amperage. But as always time restrictions might come in to play. What are your thoughts on the maths channel? Have I got it set up correctly? Or are the drop outs from my incorrectly setup maths channel.
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Re: Sensor, wiring or ring ?? (Digital)

Postby Martyn » Fri Apr 28, 2017 9:43 am

You may wish to try setting the channel coupling to AC on a +/-2V range, which will remove the 11.5V offset. You will then get your signal centred around zero so the frequency maths channel can just be freq(A). This may clear up the signals you are seeing :)
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Re: Sensor, wiring or ring ?? (Digital)

Postby RYM6746 » Fri Apr 28, 2017 11:51 am

I did try the AC coupling to begin with and wasn'tvery happy with the resolution of the signal. I will try it again and hopefully post the results up.
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Re: Sensor, wiring or ring ?? (Digital)

Postby RYM6746 » Sat Apr 29, 2017 12:00 am

I've managed to get a capture AC coupled which has increased the amplitude. But the maths channel still has spikes in it when the wheel is and isn't turning probably due to the ripple from the alternator.as seen in capture 5 and 6. What I have noticed is with out the engine running i get a much cleaner signal on DC, the normal voltage operating range is lower.
Attachments
Hyundai_i10_2010_Petrol_ABS sensor digital GOOD.psdata
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Hyundai_i10_2010_Petrol_ABS AC coupled 2.psdata
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Re: Sensor, wiring or ring ?? (Digital)

Postby RYM6746 » Sat Apr 29, 2017 12:18 am

Here is a good capture that is very interesting. Its both front wheel speed sensors at the same time. I have actually fitted a brand new genuine sensor to the offside front (suspect bad circuit/sensor) at this point. Both have the same voltages and continuously keep pumping out a square waveform, with identical maths channels set up. But one maths channel still keeps showing more drop outs than the other. How is this possible? I need some help on this one :?: The purple maths channel is the wheel that was logging a fault intermittently. It hasn't logged a fault since I've fitted a sensor but it was intermittent so I cannot be sure I have fixed it. Only time will tell, I will keep you posted.
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Hyundai_i10_2010_Petrol_Both front sensors comparing long timebase.psdata
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Re: Sensor, wiring or ring ?? (Digital)

Postby Technician » Sat Apr 29, 2017 12:39 am

Somebody else experienced with Pico scopes might advise differently to me here, but comparing the data you have posted I'm not convinced I am seeing a problem with the sensors IMHO.
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