used calculators, because they will continue to be used
as backup equipment. The calculators used for
computations of surface observational data are the
pressure reduction computer, the psychrometric
computer, the density altitude computer, and the true
wind computer.
Proper care of all plastic and metal calculators is
important to keeping these devices functional. The
plastic and metal surfaces should be kept free of any
sand or abrasive particles. Clean the space between
adjacent plastic or metal disks by drawing a piece of
blotter paper through the space. Wash the calculator in
freshwater, using a mild detergent if necessary. Dry the
calculator thoroughly. Use ordinary desk blotter paper
to dry the space between disks. Do not use solvents to
clean calculators; solvents will dissolve or soften the
plastic.
Store plastic and metal calculators in a cool, dry
location. If the storage temperature exceeds 140°F, the
Figure 2-46.—CP-402/UM pressure reduction computer.
Figure 2-47.—CP-165/UM psychrometric computer.
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