Connect with us

Hall Effect : sphere of sensitivity?

Discussion in 'Electronic Basics' started by Beowulf, Feb 4, 2004.

Scroll to continue with content
  1. Beowulf

    Beowulf Guest

    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?
     
  2. CFoley1064

    CFoley1064 Guest

    From: Beowulf
    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
     
  3. John Larkin

    John Larkin Guest

    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
     
  4. Beowulf

    Beowulf Guest

    ..
    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!

    :)
     
  5. CFoley1064

    CFoley1064 Guest

    From: Beowulf
    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
     
  6. Tim Auton

    Tim Auton Guest

    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
     
  7. Beowulf

    Beowulf Guest

    ...

    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!) :)
     
  8. ------------
    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.

    ------------------
    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
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-