? on Mr Hall Effect

[Carlo Putter]

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Yes you are correct.
The only thing that are moving in the Hall-effect sensor is the =
electrons passing through it (DC-current). So is would give a constant =
voltage for a constant magnetic field. (Permanent magnet). How I think =
the hall-sensor is working is:

In the sensing unit there is a permanent magnet, alligned with the =
hall-effect sensor, pointing to the centre of the sensing wheel. When =
the sensor passes one of the teeth of the sensing wheel, the magnetic =
field is concentrated to the area of that tooth. This causes the =
magnetic flux through the hall-effect sensor to be higher than the case =
without the thoot, which would then result in a "higher" output voltage =
of the sensor. Thus if the sensor is passing the teeth of the gear, the =
resulting output would be a "square" wave. Remember that the hall-effect =
sensor is constantly subjected to the permanent magnetic field, thus the =
resulting square wave would have an ofset. (That is if no compensating =
circuitry is build into the sensor).

Carlo

-----Original Message-----
From:	Kevin Vannorsdel [SMTP:kv at us.ibm.com]
Sent:	Tuesday, November 10, 1998 6:43 PM
To:	diy_efi at efi332.eng.ohio-state.edu
Subject:	Re: ? on Mr Hall Effect


 I have no knowledge of this particular sensor but correct me if I am =
wrong....
The Hall Effect (proper) is not a transient thing right?  My =
recollection is
that the Hall Effect occurs in the presence of a magnetic material... =
not only
in the "passing" of it.

Time to dig out my Physics 203 book!

________________________________________________
  Kevin Vannorsdel     IBM Arm Electronics Development
    408-256-6492                Tie 276-6492     kv at us.ibm.com



owner-diy_efi at efi332.eng.ohio-state.edu on 11/10/98 08:35:25 AM
Please respond to diy_efi at efi332.eng.ohio-state.edu
To: diy_efi at efi332.eng.ohio-state.edu
cc: diy_efi at esl.eng.ohio-state.edu
Subject: Re: ? on Mr Hall Effect




I think the teeth improve the magnetic coupling between the powered
coil and the signal coil.   I would almost guess that the powered coil
was powered by something other than a DC signal.  Basically the power
coil to the signal coil is a transformer and putting the metal near it
changes how the transformer acts and that is what is detected.

I do not think a DVM would be able to detect the signal good enough.
There would be only one change when you moved it in closer, and that
would pass by the DVM way too fast to catch.

All of those devices work on transients that are probably too fast to
catch with a DVM.  If you have it, you may try feeding it into a sound
card and see what the wave really looks like.  Also if you where
spinning the disk past the sensor you would be able to detect the
level out the output signal (average level) changing, but would owuld
not be able to detect any of the waveforms themselves.  You might in
the case be able to put the DVM on HZ (if yours had this) and count
the number of teeth.

   Roger

 On Tue, 10 Nov 1998, Bruce Plecan wrote:

> In the past, I done some trouble shooting with Hall Effect Devises.
> Now, for the first time I hooked a meter to one with it sitting on the
> table.  The one I'm starring at is a Toyota, it has a red lead, a =
white
> lead, and a sheilded cable with ground.
>   So being the Cone Shaped Hat Wearer that I am, I did the following.  =
Using
> a 9v battery, I grounded it to the shell of the sensor
> applied + to the read lead, grounded the meter (DVM on V),
> hooked the meter's lead to the white wire, and then tested it.
> The test being held a gm crank disc near the tip of the toyota
> sensor.  The meter just flickers as I expose it to the metal?.
> I thought it would open and close as the metal came close to it?,
> yes/no?..
>   In various gm training references they show a pattern like
>
>        ___       ___       ___       ___
> ___I      I___I     I___I      I___I      I
>
> Can someone splain this to me, or refer me to an online source for
> accurate info?.
> Thanks
> Bruce
>
>


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