hi I'm Fran this is the go direct three
axis magnetic field sensor don't worry
though
it says three axis on it but when you
turn it on and connect it to graphical
analysis you'll only see one channel
measuring one direction of magnetic
field and it's easy to use so we're
gonna use it to take a look at some
magnetic fields starting with this one
and here I have a cow magnet I have
drawn the magnetic field around the cow
magnet and labeled it with north and
south so first I'm going to turn on the
magnetic field sensor by pressing this
button then the red light flashes
showing that the sensor is ready to
connect
I'll choose sensor data collection on
graphical analysis and using the ID
number on the back of the sensor find
that sensor in my list in graphical
choosing connect once it's connected not
only is it connected to measure in the
direction of the wand but the blinking
light turns to green I'm going to click
done and since what I'd like to do first
is just use this to check the direction
of the magnetic field and which pole is
which on the magnet I'm going to switch
my view to the meter view so now if I
line up the direction of the sensor wand
with the direction that the magnetic
field lines are pointing towards the
South Pole
I get a positive number on the screen
showing that this is indeed the South
Pole of the magnet when I move the
sensor around so that it is pointing
towards the North Pole now the magnetic
field line is pointing opposite the
direction that the wand is pointing in
since the directions are opposite each
other we get a negative reading on the
meter screen I can use this to test the
polarity of other magnets
for example perhaps you've seen the
experiment where you take a nail and you
use a magnet to magnetize that nail I'll
test this by picking up a paperclip so
you can see that yes this nail is
magnetized but which end is the North
Pole and which end is the South Pole
in order to test that I can just put my
sensor right up to the end of the nail
since I'm getting a negative value the
head of the nail the place where you hit
it with the hammer is the North Pole and
the pointy end gives me a positive value
so that's the South Pole I can also use
this on magnets that I found in a box in
my closet don't know how long they've
been in the closet when I hold the
sensor up to the end that's labeled with
an N you can see I'm getting a positive
number so that means that this magnet
that I got from my closet is actually
mislabeled you may want to check out the
magnets in your closet so in addition to
figuring out the direction of the
magnetic field you can also use this for
a number of experiments so I'm going to
do an experiment with this remove the
magnet from my paper and place it on the
table and what I'd like to look at is
the magnetic field as I take the sensor
and move it along so in order to do that
I'm going to need a ruler which I'll
tape to the table that so that it
doesn't move I'm going to use the
position of the magnetic field sensor to
determine where I'm going to measure the
magnetic field and obtain a graph so I'm
going to go back to the graph screen one
graph I'm going to change the data
collection mode so that I
can use events based events with entry
I'm going to have my event name be
position which I'll measure in
centimeters and then before I actually
start taking measurements I'd like to
make sure that I am making my
measurements without the influence of
magnets other than this one and also
without the influence of the Earth's
magnetic field so I'm actually going to
temporarily take away this magnet and
then zero the sensor reading so that's
going to eliminate the Earth's magnetic
field from the measurements that this
magnetic field sensor takes after I've
zeroed it I can return the magnet to its
place and now I can begin my experiment
in all cases when I measure the position
of the magnetic field sensor I'm looking
at these dots that are on the top and
side of the sensor that shows the
location of the actual chip that's
making the measurements so I'm going to
start at the zero position
zero centimeters and I'll keep that
point then I'll move this to the one
centimeter location select keep enter
one and keep that point I'm going to go
all the way to the end of the ruler
and there we are with 30 measurements
let's take a look at the graph I'm going
to change the appearance of the graph to
make it a little bit easier by adding
lines to the graph so now you can see
that the shape of the graph is positive
for the first bit is negative in the
middle and then is positive at the end
does this match what we know about
magnetic fields well let's compare to
our magnetic field chart I started
taking measurements with the field
sensor in this area relative to the
location of the magnet and you can see
that the magnetic field line is oriented
kind of at an angle to the actual wand
of the sensor however that angle is
pointed more that direction than it is
that direction so you get a little bit
of a positive reading here as we move
this along towards the center of the
magnet the fields are very strongly in
the opposite direction that the wand is
pointing so that's where we get our
strong negative values here and then as
we bring the wand all the way past the
magnet again the magnetic field line is
crossing at an angle but this time the
angle is again more in the direction of
the wand rather than in the direction
against the wand so we get another
positive value and not as great as the
negative value from the center so you
can relate what you get in the
measurements directly to what you know
the magnetic field looks like there are
many more experiments that you can do
with this sensor for more information
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