Reccomendations Please - Multimeter/Ocilloscopes or Simple Signal Tester?

Discussion in 'Tools, Equipment & Fasteners' started by Dave, Sep 27, 2017.

  1. Dave

    Dave Pedantic Old Fart Paid Member

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    Hi Folks.

    I am having problems with the signal from Cam Position Sensor (G40) on Elaine's Mk4 1.8T AUQ.

    The thread is at the bottom of the page.
    Basically whatever I do I always get Fault Code; Signal Too High.
    I have tried a new sensor. Different shutter wheels. Disconnecting the plug. Changing the cams.
    All to no avail.
    I am wondering if it's the wiring to the ECM? I have checked for continuity and cables appear OK, although the signal cable is not very flexible at the plug.
    There are actually small cracks in the plastic close to the plug.

    Before I start messing with the cables I thought that I'd try to check the signal from the Hall Sensor.

    Multimeter/Ocilloscopes are quite expensive for just one test.
    I already have a pretty good Multimeter anyway.

    Cheapest way might be a simple signal tester like this?

    V-Checker.jpg

    Comments please?

    http://clubgti.com/showthread.php?286661-Help-Please-Mk4-1-8-20V-T-Camshaft-Sensor-Problems

    Thanks in advance,
    Dave.
     
  2. Dave

    Dave Pedantic Old Fart Paid Member

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    Found this place.
    It's actually in China!
    Lots of 'Chinese' automotive testing kit!

    OBD2 UK.jpg
    V-Checker Tech.png
     
  3. Tristan Forum Junkie

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    I can loan you a single channel one if you want.
     
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  4. Dave

    Dave Pedantic Old Fart Paid Member

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    You are a grand sSon Tris,!

    I am a little unsure what a 'single channel one' is though?[:s]

    Not been near an oscilloscope since way back when they were big metal boxes on lab. benches!

    Is it suitable for probing the output from the Sensor Plug terminals?

    Regards,
    sDa.
     
  5. Tristan Forum Junkie

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    As in it will only measure one output / sensor for waveform at a time. I used it on crank and camshaft sensors on one of the Rally cars.
     
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  6. Dave

    Dave Pedantic Old Fart Paid Member

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    Ta so Tris. Understood.

    I shall paypal some cash to your account. Is your e-mail still:
    ret*********@*****.com?

    Do you still have my address?

    Thanks once again,
    Dave.
     
  7. Jon Olds Forum Junkie

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    A cheap scope of ebay is a nice thing to have. 50 will buy you one, as not a lot of people know how
    to drive them. As its relatively low frequency pretty much anything scope wise will work
    I was trying to diagnose a similar thing with a non starting ABF, so stuck a spare ABF crank between centres in the lathe and mounted a
    probe on the toolpost.
    Tried various probes at various gaps etc and various speeds looking at the signal on the scope.
    Hope this is of some help.
    Also, you can get an adapter to bring signals into a laptop )analogue to USB effectively) and run scope software on it. Heard some good things about this, but not tried it myself.
    Jon
     
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  8. Dave

    Dave Pedantic Old Fart Paid Member

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    Thanks Jon.

    You obviously know a lot more about testing this kind of thing than I do, so what do you think about the following?
    If I am wrong, in any respect, then please fell free to make me look stupid! I am Mech. Eng. and the last time I was forced to study electronics was 45 years ago!

    So. Your comment about the lathe is interesting.

    I have a small 240V 5 rpm motor that I was thinking of making a test rig with it and use an led.
    I will mount the spare shutter wheel on the motor and rig the spare sensor in line.
    Put +12V into pin 1 and connect the led between pin 2 and pin 3 -ve.

    But, on reading up about Hall sensors I find that the output signal voltage is very low, so it may not drive an led.

    Because the Hall voltage is low I assume that the signal through a wire with high resistance will degenerate so that the ECM will be unable to read it?

    Kind regards,
    Dave.
     
  9. Trev16v

    Trev16v Paid Member Paid Member

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    Dave, about driving a LED from your hall sender.

    It depends on the hall sender, specifically what kind of output switching transistor configuration it has.

    The kind used on a 16V distributor for example are (if I remember correctly) open collector or open emitter, which in very simple terms means that you can think of the hall sender as a pair of contacts that open and close. So, to produce a square wave voltage signal from this, you combine it with a pull-up resistor, which would usually be in the order of kilo-ohms. This will provide a source that is most likely too 'high impedance' to drive a LED directly. In simple terms that means there won't be enough current to drive the LED.

    Some hall senders may have a push-pull output which means they might be able to drive a LED directly, but you'd have to read the part number off the hall sender and check the datasheet.

    So, you could connect your LED (with a 1K series resistor to protect it) just to see if it works; but if not, the best way to drive a LED is to use a buffer. This could be as simple as a single transistor and a couple of resistors.
     
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  10. Tristan Forum Junkie

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    Dave likes this.
  11. Jon Olds Forum Junkie

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    If you hope to drive the output into a LED, you need a low input current type. This still may not give you the info you need, a scope would be better
    as it doesn't put any (significant) load on the signal and just displays the voltage waveform. I can try and help over email if you think that's a benefit,
    as I'm elec based.
    Jon
     
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  12. Dave

    Dave Pedantic Old Fart Paid Member

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    Well folks, what can one say!?

    "What a grand set of human beings you all are!"

    What kindness that you took the time to help in such a detailed manner.
    Rubjonny also sent me data. At least 6 e-mails about cables, terminals, tools, etc. and good advise on which other wiring it might be worth replacing if I do re-wire the loom.

    I have only been able to help Fury Phil recently cos. that was about tools, which I believe is my forte!?
    That took little time, and little input, in comparison.

    Trev and Jon.
    Thanks for the data. The led idea is now dead! I'll build the rig but wait for Tris's scope the check the senders.
    As I said, it's a long time since I was faced with electronics calculations. 1969 I recon.
    Back then transistor radios were still a novelty, and Bosch Transistorised Ignition systems were expensive motor sport items and still used distributor points as a trigger.
    I can remember PNP and NPN semi-conductors and Fourier series, and transforms, were great fun as I love maths.

    I was reading this, but gave up after chapter 2:

    https://sensing.honeywell.com/hallbook.pdf

    Trev's short discourse was far more informative.

    Jon.
    Back to your earlier comments. I looked at lots of possible solutions including those to drive pc software.
    They look grand, if you are really into it like yourself, but I was only looking for a simple tool.
    Long term I recon. that the V-Checker tool might suit my needs.

    Tris.
    You really are a good 'un. Ta so.
    Is the yellow Mk1 still lighting up Gurteen?
    I have not seen it for 10 years or so.

    I have actually ordered one of the V-Checker probes.
    At 20 it's worth trying and I'll report on it.
    If it is any good then it will be a boon to people like myself who just want a cheap and simple checker.
    Mind you, as it's from China, it might take a month or so to arrive so don't hold your breaths.

    Kindest regards,
    And thanks once again.
    Dave.
     
  13. Sirguydo

    Sirguydo Fastest milkman in the West Paid Member

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    Dave I wasnt even born then ! lol

    Glad your getting there , whats your good lady driving at the moment since you broke her car ?
     
  14. Dave

    Dave Pedantic Old Fart Paid Member

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    I did not break it. I hardly drove it.

    The car is drivable. The only problem is starting, as the ECM has to guess when to fire plug 1.
    So it can take anything up to 5 attempts before it starts.
    The ECM seems quite able to cope with the extra ignition advance.
    Whether we are damaging it, I don't know!?

    The maximum advance is about 28 deg. BTDC. Which, funnily enough, is what you will need to run highly tuned valvers at according to the VWMS Workshop Manual!
     
  15. Dave

    Dave Pedantic Old Fart Paid Member

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    G40 Hall Sender Bench Test Rig

    I realised that my multi-meter can read milliVolts so I did not need an LED![:$][:$]
    I don't know how accurate it is. I have had it for years and it was not expensive.
    I marked the cam where the shutter wheel slots are and at 5 rpm it's easy to see the cut-off and on signals.
    This is the cheapo Chinese Hall sender. I'll put the original on the rig, if it ever stops raining, and compare outputs.
    I must admit that I expected a low reading of ZERO Volts, not 1.0 mV!?

    Hall Test 2.png
    hall test 1.png
     
  16. Rubinwef New Member

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    I am curious why add the power supply when you can use the 5 volts off of the usb port to power the circuit?
     

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