Triple Bean Balance
The triple beam balance is a rugged, inexpensive weighing instrument. It
is
named for the three beams which carry weights. A. The middle beam reads
only in
100 g increments. B. The far beam reads only in 10 g
increments.The weights in
each of these must always sit in a "notch". They
cannot be placed at
arbitrary points on the beam. C. The weight on the front
beam can be placed to
read continuously from 0 to 10 grams. The Triple Beam
Balance is a typical
mechanical balance. It has a beam which is supported by
a fulcrum. On one side is
a pan on which the object is placed. On the other
side, the beam is split into
three parallel beams , each supporting one
weight. In measuring the weight of an
object, rather than adding additional
weights, each of the three weights can be
slid along the beam to increase
their lever arm.It works just like a tetter-totter.
If you have two
people of unequal weight, the heavier person sits closer to the
fulcrum to
decrease their lever arm. Making a WeighingIn measuring the mass of
any
material ,you must always
make.............................................
two weighings!If you use a
container to hold the material, you must first weigh
the empty container.
This weight is called the tare of the container. Then you
weigh the container
with the material in it. The difference between these two
weighings is the
mass of the material.In weighing an object directly on the pan,
you must
still make two weighings. The first of these is to weigh the empty
pan!
This must be set to read 0.00 g. The triple beam balance has a
little knob under
the pan which you screw in or out to set the empty balance
to read exactly 0.00
g.So, in weighing an object directly on the pan, you
must first Zero the
balance. Only if the balance is properly zeroed, will it
weigh the object
correctly. The front beam is graduated in one gram units
0-10 (see numbers).
Each one gram interval is further divided into 10
spaces or .1 gram. When the
weight is carefully placed, its position can be
estimated to .01 or .02 g.In
reading any graduated scale....You read not only
to the smallest graduation mark
but estimate between the graduation
marks.This is called reading the scale to
the proper number of Sig Figs.