advise or help needed to measure hall output, and spewage

auditude at auditude at
Fri Feb 22 11:02:42 EST 2002

urq urq at wrote:
> ... sorry to be so frank Ken, but if you really don't even know how to
> use the tools you really should consider yourself in over your head.

Hi Steve,

No apology needed at all.  There's nothing wrong with calling a
duck a duck! :-)  I know that I am in over my head.  But I also know
that if I wasn't, I wouldn't be interested in this.  I guess the problem
is that I've gotten myself further over my head than I should, all at
once.  I'll respond to a different post to look at what it happened,
there are reasons, tho' they wouldn't be justifiable for everyone.

Being just a little over my head is what this all has been about for
me.  I had never had to rethread the spark plug holes before either,
and it was a totally new and intimidating learning experience.  I
want to do it right, even if it takes whatever time it takes.  The
waiting is getting old tho'.

> Perhaps the thing for you to do is to find someone in your area who is
> familiar with using an oscilloscope and have them work with you.

Well, I learned a little bit just recently, such as I can get least get
some information using a dwell meter, as opposed to an o-scope.
Reading emails, it can be difficult for me to understand what is
posted, because it can be interpretted different.  I usually pick the
wrong interpretation.  Either that, or I'm overly careful not to, and I
end up asking questions about minute details that most would
consider common sense, because they are already in the correct

I went through this the other day with my mom.  She was telling
me that feng shui or whatever dictated that I, or my sign in the
Chinese zodiac, should avoid facing east, at least for this year.
We got into almost an argument about what that meant, when I
asked her to clarify what the word "facing" meant.  I took it to mean
the direction my face was facing, and she meant it to be basically
where the top of my head was facing, or which part of the room my
bed was on, or which direction the room I was in "faced".  The fact
that she assumed I shared the same understanding of the word,
made it a more protracted discussion than it needed to be.  (my
logic, "what if there is no house or bed, then which way?")  But

> Perhaps you can work with the EFI vendor ... seems to me you actually
> paid money to them for it, they might want to provide some sort of
> support!

Yeah, they haven't charged me, and supposedly won't until it ships.
 So, they haven't seen any of my money yet.  And to think I was all
set to take the hit the last business day of '01, which was the end
of the manufacturer-driven sale period.

>  I haven't really done a lot of investigation into such
> systems, but I doubt that many are designed with the intention of
> working with the various signals different manufacturers use.

This is true.  However, the vendor was actually the one that asked
about the stock sensor system and it's function.  After I reported
back the way the stock system works, they replied that they could
use those inputs, basically the rpm and the hall.  All I had to do
was tell them where the rising and falling (falling and rising) edges
of the hall sensor output were, so they could program it to use
them.  That, and my tangental circuit project, are what is currently
holding up the manufacture of the ecu.

> The Hall signal is pretty much a "digital" signal ... it is in one
> state when the sender is blocked by the shutter and the other when it
> is not.  The speed sensor signal looks pretty much like a sine wave
> ... and the reference sensor has a very interesting signal which is
> the result of a single metal pin flying up and past a coil of wire.
> As important as knowing the individual signals is understanding how
> they work together ... and this takes a good bit of work to understand
> in detail.

I'm understanding this more.  Is the hall sensor visible on the unit,
or would an exploded drawing be necessary in order to get a
mental picture of the parts?

The reference sensor is the one Orin said needed to be
conditioned.  While I was pointed toward the schematic posted on for the MAC11B circuitry, my next question was if I
needed to replicate that whole circuit, or a portion of it, or?  I
learned a little bit about signal conditioning off the 'net.

For example, reading into the descriptions you and others have
posted on the operation of the hall sensor, it seems like the hall
sensor output is constant, and the outgoing signal is "blocked" by
the shutter.  This reads to me as being different than if the signal
generation itself (in other words, the input to the hall sensor) is
blocked by the shutter.  Perhaps this has nothing to do with my
intended usage of the hall output, but in understanding the way it
works, I am left wondering.

If I were continuing to build the circuit I wanted, then it would be
one that only sent a signal to the ecu when the hall sensor output
is low and the reference sensor is high.  Still sounds easy to me,
but screw that idea, the stock hall output is hard enough for me, for

> Perhaps the best reference I've seen is the Audi IST documents for the
> urq ... which seem to still be available from Dyment.  Other than the
> relocation of the pin in the flywheel the info in the IST applies to
> the MC as well. Be advised that even the IST docs aren't going to
> answer all of your questions!  One other idea ... see if anyone wants
> to work with you on this on the "torsen" list.  Since the bandwidth
> there is much more reasonable I can still monitor that list from my
> e-mail at work ... perhaps I might even have time to help ...

Thanks for those ideas.

> I would love to be able to help you with you project, and I'll bet
> there are others on the list who would like to do likewise ... but
> really I didn't even have the time to put this message together ...
> seeing that now it is after 7 I really need to get going!

Yes, I totally understand about the time thing.  This is my project,
and I find it difficult to get the time to spend on it!

> Good luck with your project Ken!  I do hope this note helped!

I do appreciate the note, I think it does help.

Best regards,


I spewed:
> >
> > My efi project is pretty much stalled.  Motor is a MC-1 with
> > MAC11B setup/pieces, efi ecu is LinkPlus, car is an '85 4ksq.
> >
> > I'm waiting for myself to acquire tools and skills to get
> > information about the stock ignition system triggers.

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