Hall Effect : sphere of sensitivity?

[Beowulf]

I built a gaussmeter using this website
http://my.execpc.com/~rhoadley/magmeter.htm
The gaussmeter seems to have a "sphere of sensitivity"
of about 12 inches or less. I guess I do not understand
this, that is what is a Hall Effect gizmo, and what
affects its sphere of operability-- how can I increase
its sphere that surrounds it for affecting it? I know
I sort of asked this question in an earlier post, but
I do not think I was clear in that query. I want to
somehow increase the distance from the gaussmeter
that the Hall Effect component is able to sense an
electromagnetic field. Any way to do this? And what
the heck is a Hall Effect gizmo-- is it a switch, or
a transistor of some sort?

 

[CFoley1064]

From: Beowulf beowulf@nowhere.net
Date: 2/4/04 3:53 PM Central Standard Time
Message-id: <pan.2004.02.04.21.53.23.537769@nowhere.net

I built a gaussmeter using this website
http://my.execpc.com/~rhoadley/magmeter.htm
The gaussmeter seems to have a "sphere of sensitivity"
of about 12 inches or less. I guess I do not understand
this, that is what is a Hall Effect gizmo, and what
affects its sphere of operability-- how can I increase
its sphere that surrounds it for affecting it? I know
I sort of asked this question in an earlier post, but
I do not think I was clear in that query. I want to
somehow increase the distance from the gaussmeter
that the Hall Effect component is able to sense an
electromagnetic field. Any way to do this? And what
the heck is a Hall Effect gizmo-- is it a switch, or
a transistor of some sort?

Here's a good (non-technical) resource on different types of magnetic field
sensors, courtesy of Sensors magazine:

http://www.sensorsmag.com/articles/1298/mag1298/index.htm

The article includes a brief non-technical description of the Hall effect in
semiconductors. The IC you're using is pretty good for a hall effect sensor.
The only way to get a greater "sphere of operability" (intersting way to
describe it) with your sensor is to get a more powerful magnet. From several
feet away, you're probably going to be at the point where the earth's magnetic
field would be the dominant force (try seeing from how far away you can deflect
a compass needle with your magnet) or that you would have to increase the power
of your magnet to almost Wile E. Coyote cartoon-type levels to detect it with a
hall effect sensor. Remember the rhyme, "The Hall effect is a small effect".

There are other methods of measuring magnetic fields, but it might be better to
take a look at other methods of sensing. There are any number of ways of
detecting the distance of an object at 2 to 12 feet feet or so. Ultrasonic
sensors, retro-reflective opto sensors, various contact and non-contact methods
come to mind. Possibly you could describe your application?

Chris

 

[John Larkin]

On Wed, 04 Feb 2004 15:53:23 -0600, Beowulf <beowulf@nowhere.net>
wrote:

I built a gaussmeter using this website
http://my.execpc.com/~rhoadley/magmeter.htm
The gaussmeter seems to have a "sphere of sensitivity"
of about 12 inches or less. I guess I do not understand
this, that is what is a Hall Effect gizmo, and what
affects its sphere of operability-- how can I increase
its sphere that surrounds it for affecting it? I know
I sort of asked this question in an earlier post, but
I do not think I was clear in that query. I want to
somehow increase the distance from the gaussmeter
that the Hall Effect component is able to sense an
electromagnetic field. Any way to do this? And what
the heck is a Hall Effect gizmo-- is it a switch, or
a transistor of some sort?

There isn't really a sphere. The Hall chip is a tiny semiconductor
that used the Hall effect (google that for details) to detect the
magnetic field intensity right *at* the chip. It doesn't know how far
the magnetic source is, just how intense the field is locally.

Are you sensing a magnet? The field from a magnet is a dipole, and its
field strength falls off with the cube of distance. So if your Hall
sensor was twice as sensitive as it is now, the range would only
increase about 25%.

John

 

[Beowulf]

On Thu, 05 Feb 2004 03:14:31 +0000, CFoley1064 wrote:
.....

There are other methods of measuring magnetic fields, but it might be better to
take a look at other methods of sensing. There are any number of ways of
detecting the distance of an object at 2 to 12 feet feet or so. Ultrasonic
sensors, retro-reflective opto sensors, various contact and non-contact methods
come to mind. Possibly you could describe your application?

Ok now I know many reading this are going to laugh, but do not pre-judge.
My application is that of paranormal investigation, ghosthunting. Now I
for one do not believe in ghosts, but I do not disbelieve in them either.
With new theories in physics of string theory and quantum mechanics, I
am not eliminating the possibility that what some might experience as a
ghost sighting may possibly (slim perhaps) be an entity from a parallel
universe. So as a scientist myself I would like to try a ghosthunting
expedition and hook up probes like gaussmeters, motion detectors,
thermal sensors, and collect data to see if anything unusual occurs in
an alleged highly haunted house.

So, thus my application, and need to detecting EMF signals at as great a
distance from a Hall Effect component as possibly. But it sounds like
this is not too practical, that one must almost put the gaussmeter into
the specific area where one believes a potential EMF field (ghost?)
to exist at the moment of measurement?

Ok go ahead and laught-- like is too short not to chuckle!

 

[CFoley1064]

From: Beowulf beowulf@nowhere.net
Date: 2/5/2004 7:02 AM Central Standard Time
Message-id: <pan.2004.02.05.13.02.24.954833@nowhere.net


Ok now I know many reading this are going to laugh, but do not pre-judge.
My application is that of paranormal investigation, ghosthunting. Now I
for one do not believe in ghosts, but I do not disbelieve in them either.
With new theories in physics of string theory and quantum mechanics, I
am not eliminating the possibility that what some might experience as a
ghost sighting may possibly (slim perhaps) be an entity from a parallel
universe. So as a scientist myself I would like to try a ghosthunting
expedition and hook up probes like gaussmeters, motion detectors,
thermal sensors, and collect data to see if anything unusual occurs in
an alleged highly haunted house.

So, thus my application, and need to detecting EMF signals at as great a
distance from a Hall Effect component as possibly. But it sounds like
this is not too practical, that one must almost put the gaussmeter into
the specific area where one believes a potential EMF field (ghost?)
to exist at the moment of measurement?

Ok go ahead and laught-- like is too short not to chuckle!

Not laughing at all, Beowulf. If you look at the article, you'll see the more
sensitive types of magnetic sensors. It sounds like you're going to need
something a lot more sensitive than a Hall effect sensor, and probably
something which will be able to sense magnetic fields (probably 3-dimensional
readings) which are far weaker than the earth's magnetic field.

Looking at the article, I'd guess you might be interested in looking at flux
gate magnetometers. That's beyond my area of expertise.

You might want to try calling Bartington Instruments, and asking them about
their triaxial fluxgate magnetometers. Specifically, you would be looking at
their MAG-03 line. Check their website first, and get an idea of the
sensitivity you want before you call for pricing. They'll sell you the sensor
and accessories, but they may not be very enthusiastic about your line of
inquiry. Remember that, if you're measuring static fields, you may be swamped
out by the earth's magnetic field, and also any iron or ferrous metal in the
vicinity. You may want to look for a haunted house which is made entirely of
plastics and non-magnetic materials to do your research, or disassemble and
rebuild one with non-ferrous pipes, nails, &c..

http://www.bartington.com/mag03.htm

You might get a better reception for your questions at alt.paranormal.

Good luck with the ectoplasm, Beowulf.
Chris

 

[Tim Auton]

Beowulf <beowulf@nowhere.net> wrote:

On Thu, 05 Feb 2004 03:14:31 +0000, CFoley1064 wrote:
....
There are other methods of measuring magnetic fields, but it might be better to
take a look at other methods of sensing. There are any number of ways of
detecting the distance of an object at 2 to 12 feet feet or so. Ultrasonic
sensors, retro-reflective opto sensors, various contact and non-contact methods
come to mind. Possibly you could describe your application?

Ok now I know many reading this are going to laugh, but do not pre-judge.
My application is that of paranormal investigation, ghosthunting. Now I
for one do not believe in ghosts, but I do not disbelieve in them either.
With new theories in physics of string theory and quantum mechanics, I
am not eliminating the possibility that what some might experience as a
ghost sighting may possibly (slim perhaps) be an entity from a parallel
universe. So as a scientist myself I would like to try a ghosthunting
expedition and hook up probes like gaussmeters, motion detectors,
thermal sensors, and collect data to see if anything unusual occurs in
an alleged highly haunted house.

I'll not laugh, but I will caution you against making and using highly
effective sensors which you don't fully understand. I'm sure you could
build a hugely sensitive magnetic field sensor, far more sensitive
than an off-the-shelf hall-effect sensor, but unless you know
*exactly* what the sensor does and how it works you are highly likely
to misinterpret results. The more sensitive your sensor the more
likely you are to pick up noise and the more likely it is that that
noise will look like signal. In your application, even more than other
avenues of science, verifiable results are crucial.


Tim
--
The .sig is dead.

 

[Beowulf]

On Thu, 05 Feb 2004 20:18:17 +0000, CFoley1064 wrote:
...

vicinity. You may want to look for a haunted house which is made entirely of
plastics and non-magnetic materials to do your research, or disassemble and
rebuild one with non-ferrous pipes, nails, &c..
...

LOL-- ok now we just have to build a plastic home and get a few people to
live in it and then kill themselves or somebody else to have it haunted!
(smile-- just kidding of cours!)

 

[R. Steve Walz]

Beowulf wrote:

On Thu, 05 Feb 2004 03:14:31 +0000, CFoley1064 wrote:
....
There are other methods of measuring magnetic fields, but it might be better to
take a look at other methods of sensing. There are any number of ways of
detecting the distance of an object at 2 to 12 feet feet or so. Ultrasonic
sensors, retro-reflective opto sensors, various contact and non-contact methods
come to mind. Possibly you could describe your application?


Ok now I know many reading this are going to laugh, but do not pre-judge.
My application is that of paranormal investigation, ghosthunting.
------------

Now the thing you need to learn about Science, is that an important
thing a Scientist will do is eliminate all the ridiculous unreasonable
possibilities because there are afterall an infinity of them, and yet
only a single accurate and therefore correct explanation for phenomena.

It seems almost prejudicial to eliminate an infinity of options for
the way things MIGHT be, based on just a few example experiments of
their class, but it is an important skill for am actual Scientist.

With new theories in physics of string theory and quantum mechanics, I
am not eliminating the possibility that what some might experience as a
ghost sighting may possibly (slim perhaps) be an entity from a parallel
universe. So as a scientist myself
------------------

You REALLY need to learn everything that HAS been done to eliminate
such an unreasonable guess, before wasting your own time repeating
it. It's fine to investigate new things, or old things in new ways,
as long as it IS actually new, and not just repetitive stubborness
based on a preference for a way you'd LIKE things to be, instead of
the way they ARE. Find out first how many of your experiments have
already been done to death with disappointing results. THEN see if
the supposed "paranormal" seems a likely prospect for new discovery!

-Steve
--
-Steve Walz rstevew@armory.com ftp://ftp.armory.com/pub/user/rstevew
Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!!
http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public