Figure 1-2. Prescription balance.
c. Weights. The most accurate balance is worthless unless you use accurate
mass standards or weights (see figure 1-3). If either the balance or the weights are
inaccurate, an erroneous weighing will result. Good weights are usually made of brass
and are available in various styles and shapes. Those that resemble coins in shape
should not be used. Weights must be stored in their container at all times when not in
use and must not be handled with the fingers. Touching weights with the skin leaves
deposits of moisture, body oils, and other foreign particles on the weights and adds to
their weight. These deposits may also react with the metal to cause further
inaccuracies. Forceps are included in the weight containers for correct handling. USE
THEM!
d. Technique of Weighing. Before attempting to make a weighing, make
certain the balance is level, on a solid support away from drafts, and the pans are in
equilibrium (in balance). To level the pans, release the beam lock and allow the pans to
swing freely. If the pointer swings an even number of divisions to each side of the
scale, your balance is in equilibrium. If, however, the pointer swings unevenly, you
must adjust the balance. To bring the balance into equilibrium, raise or lower the
adjustable legs at the base of the balance until the proper swing is obtained.
MD0809
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