? on Mr Hall Effect

Thu Nov 12 07:36:36 GMT 1998

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Correction
I am in the power electronics field and I assure you that there are =
Transistors with gates.
They are called IGBTs (Insulated Gate Bipolar Transistors). These =
devices are very common is power electronics, reason: Good on state =
charactaristics (High current [up to 3kA] low on-state voltage [<2.5V]), =
High blocking voltage [recently 3.6kV], Easy turn on and of [mosfet =
input characteristics].

The easy turn-on and off is the major advantage, if you ussed an BJT =
that could conduct 3kA with  Beta of 5 then you base current would be =
600A !!!! cool!!! what a large base drive circuit you need, not even to =
think of the lossed in you circuit !!!!

Cheers
Carlo

-----Original Message-----
From:	Kevin Vannorsdel [SMTP:kv at us.ibm.com]
Sent:	Tuesday, November 10, 1998 8:50 PM
To:	diy_efi at efi332.eng.ohio-state.edu
Subject:	RE: ? on Mr Hall Effect

 No dis-respect intended (absolutely no flame) but I can't let this one =
slide...
I work with transistors every day-  never heard of a bipolar one with a =
"gate"
and certainly never heard of any transistor getting turned on by a =
magnetic
field (at least not one of practical magnitude).

OK--  thyristors (SCR's and Triacs)  may be considered bipolar devices =
and do
have terminals labeled "gate"---   I wouldn't call these things bipolar
transistors though.

Many electronic devices can be activated by an *electric* field and most
certainly by light... (as is the case with the phototransistor (or any
transistor))

Here is what "Physics"  second Edition by Tipler says:
-----------------------
"The force exerted by a magnetic field on a current-carrying wire is =
actually
exerted directly on the charge carriers in the wire, the electrons.  The =
force
is transferred to the wire by the forces which bind the electrons to the =
wire
at the surface.  Since the charge carriers themselves experience the =
magnetic
force when a current-carrying wire is in a magnetic field, the carriers =
are
accelerated toward one side of the wire.  This phenomenon, called the =
Hall
Effect, allows us to determine  the sign of the charge on the =
carrier......  It
also provides a convenient method for measuring magnetic fields.  "
-----------------------
The section goes on to discuss how you can measure this Hall effect (the =
higher
density of electrons at one edge of the conductor)  by measuring the =
voltage
difference across the end of a flat bar carrying current in a magnetic =
field.

Note that there is no transient behavior here-   only a presence of a =
magnetic
field and a current carrying conductor.

Just in case anyone else was interested...

comments invited.

________________________________________________
  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 10:16:12 AM
Please respond to diy_efi at efi332.eng.ohio-state.edu
To: diy_efi at efi332.eng.ohio-state.edu
cc:
Subject: RE: ? on Mr Hall Effect

What  I recall of Hall Effect devices:

A bipolar transister
Gate can be turned on by the presence of a magnetic field.
The hardwired gate connection can be biased to alter the magnetic =
"turn-on"
threshold.

Similar to a photo-transistor in operating theory.

Regards,
Tom Butler

> -----Original Message-----
> From: Kevin Vannorsdel [SMTP:kv at us.ibm.com]
> Sent: Tuesday, November 10, 1998 12:43 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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