| Basic
Units of Measurement
It is
now the accepted practice in the Industry to use a Metric
system based on the International Standard System of Units
called "SI" (Système International). This system has now
been adopted in the writing of the National and International
Standards for all issues concerning fans and air performance.
However, there is still enough documentation in use throughout
the world for us to have to be aware of Imperial or "I-P"
units and one or two other local deviations from the basic
SI system. Some conversion factors are given in the following
table. Multiply the "Alternate" unit by the conversion factor
to obtain the "Preferred" unit.
Units
commonly found in Fan or System Performance Specifications:
To avoid
using very large or very small numbers, there are "Multiplying
Prefixes".
Examples:
gigahertz (Ghz), megawatt (MW), kilometre (km), centimetre
(cm), microsecond (us), nanometre (nm), picofarad (pF)
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