Ask A Scientist General Science Archive

name         Rima W.
status       educator
age          30s

Question -   What instructions should I give to my students to use the
triple beam balance?
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Rima,

1.  Explain how to zero and/or calibrate the balance. Use a reference mass
to make sure the balance is operating correctly.

2.  Demonstrate the correct procedure for applying the load -- that which is
to be weighed. Load must be applied gently until the weighing pan reaches
"bottom." Load should likewise be removed slowly so the beam does not make
any sound as it swings to rest.

3.  Demonstrate how to move the reference masses along the beam during the
weighing process. Move masses in order (one-at-a-time, largest to smallest)
until balance bottoms over-center with each. Then move the smallest balance
to reach equilibrium. Equilibrium is established when up-swing distance
equals down-swing distance -- it is not necessary to wait until the pointer
stops on the zero mark. At equilibrium, the beam should swing freely
throughout its range -- no signs of hesitancy or drag.

4.  Demonstrate how to clean it of spills. If the weighing pan is removable,
show students how to take it off and how to clean it -- depending on the
nature of the spill. By the way, balances are not ordinarily used to weigh 
liquids
because of potential for spills. Never weigh corrosives without extra safety
precautions.

5.  Demonstrate the correct procedure to ready it for future use, storage,
or moving. The balance should be transported and stored with the largest
reference mass moved out to the end of the beam so that the instrument is not
sitting "balanced."

In addition, you might also take the time to explain the difference between
the terms, "mass" and "weight." Balances are mass measuring instruments that
can give correct results  in any gravitational environment. This is not true
for scales.

Regards,
ProfHoff 501
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