Ohm's resistance?????
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Thread: Ohm's resistance?????

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    nrj
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    Ohm's resistance?????

    anyone know what it should be for a 1.4 8v MPi astra mk3 m/94 crankshaft sensor?

    also are all the 8v sensors the same, ie same part no????
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    teh correct way to test the sensor is too hook up a metre switched to AC volts and crank the engine. you should get spikes up to 5 volts.

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    nrj
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    Yer that way will tell me if the into to the sensor is ok, but not if the sensor itself is down.
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    If you've got access to some electrical test equipment, you'll need an oscilloscope and a differnetial probe (photo):



    This is what the waveform looks like:



    The sine wave gives the ECU the RPM signal and the large SPIKE tells the ECU it's position, hence it being called a CAS (Crank angle sensor). the spike is caused by the un-toothed part of the toothed disk.

    Happy testing, Scott
    astragte.tk
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    lol, you could have triggered it a bit better!
    Brian Sidebotham.

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    I want a scope.

    I miss twidling with them and looking like I know what I'm doing.

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    did it that way on purpose to see it in the middle of the screen!

    But just for you Brian S, a nicely triggered one!




    lmao
    astragte.tk
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    Wahey!

    I have a Gould DSO too

    Chris, keep an eye out on Ebay, they come up very cheap nowaday's
    Brian Sidebotham.

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    This one was 40 notes a few years back, it now a little worse for wear as it lived a few feet away from one of my Tannoy 15" dual concentrics for a while... I didn't think at the time how poweful the magnet could be. Now the right hand side ot the trace rises, while the lefthand side is fine!! Bugger.

    I want my FLUKE digital one back that i used to work with... but i haven't got 3k to spare.
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    here are some waveforms I took of the sensor output on my 20XE :

    http://homepage.ntlworld.com/retro.s...1_cranking.jpg
    http://homepage.ntlworld.com/retro.s...2_cranking.jpg
    http://homepage.ntlworld.com/retro.spect1/cs2_idle.jpg

    cs1 is the later plastic type, cs2 is the metal version.

    people say the metal version is better - and it is - see how it outputs a much stronger signal.

    also notice how the signal strength increases with rpm.

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    good god

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    that's a tektronix TDS360 scope btw, if we're talking scopes - has a floppy drive built in - very useful!

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    used one at my last place which had a printer built in, and 4 channels, all in different colours! RS232 link to a pc etc...

    That cost a small mortgage!
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    Gary the show off.

    Work were throwing out a pair of HP digitizing scopes (200MHz beasties) in a lab clearout. But some helpful bugger said they should be given to another dept that does transport design.

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    wtf just try another sensor instead of zapping it with some glorified 1950's tv. they only about 30 quid from autovaux (the sensor, not the crappy looking tv lol)

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    Quote Originally Posted by Gary
    here are some waveforms I took of the sensor output on my 20XE :

    people say the metal version is better - and it is - see how it outputs a much stronger signal.

    also notice how the signal strength increases with rpm.
    Thats some difference between the plastic and metal ones!!!

    The voltage wil go into the 100's given some welly! must be a clever input circuit in the ECU to read small values and also cope with the massive voltages!
    astragte.tk
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    Quote Originally Posted by sb_scottmonkey
    The voltage wil go into the 100's given some welly! must be a clever input circuit in the ECU to read small values and also cope with the massive voltages!
    I believe the ADC works simply on the 0v cross, everything else is dumped.

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    Quote Originally Posted by 16vastra
    wtf just try another sensor instead of zapping it with some glorified 1950's tv. they only about 30 quid from autovaux (the sensor, not the crappy looking tv lol)

    Isn't she a beaut...

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    But it's got to pick out the angle spike... although i suppose that just wouldn't give anything at that time, as it's not crossing zero for a few "cycles" it just notices the blank patch rather than the spike it'self!
    astragte.tk
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    I'm very lucky as I work in the eng. test dept of our company.. and sooner or later equipment is replaced or obsoleted

    I won't mention the other bits I have then or the electronerd talk in this thread will be short circuited by drool

    glorified 1950s TV lmao

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    OMG! that thing'll steralise you!!!!
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    yes - most ECUs use the same zero crossing detector, a dedicated little IC I forget the name of.

    I was mucking around with mine as I though the CAS signal was the problem.

    it turns out that this was:

    http://homepage.ntlworld.com/retro.spect1/12v_noise.jpg

    it was screwing up the ECU above about 5.5k rpm.. causing it to see roughly half the true rpm - amazing the engine wasn't leaned out to self destruction really.

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    We used to have fun playing football with 1KV charged electrolytics!... but of course we'd solder longer legs to it beforehand!!

    Would give a nice crack if you hot it in the goal (steel cabinet!!)
    astragte.tk
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    what was causing the noise?
    astragte.tk
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