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From: Lew Hodgett (no email)
Date: Thu Aug 19 1999 - 21:12:47 EDT
Some basic illumination engineering.
Something to consider in the discussion of various lamp sources is a
thing called "Mean lumen output".
Essentially, is an expression of the efficiency of conversion process of
a lamp source over it's life. It is number without units. Strictly a
percentage.
It is not to be confused with the efficiency of conversion process of the
lamp source itself which is the lumens/watt rating but rather it is an
expression of efficiency of conversion process over the life span of the
source.
Incandescent sources are rather good, around 90%. They don't deteriorate
much over the life span.
Halogen and metal halide are only around 80% max. They start out with a
bang, but fall off rapidly.
Bottom line:
Halogen does well in low operational hour applications such as
supplemental task lighting (desk lamps, etc), stage lighting, sporting
event lighting and automobile car lot lighting.
Long operational hours; however, are quite another matter. Halogen
doesn't quite cut it for general purpose or high operational hour
applications such as an industrial factory.
For you engineering types, the area under the curve will get you every
time if you are not careful.
HTH
Lew
S/A: Challenge (Under construction, still fairing in the Southland)
Visit <http://home.earthlink.net/~lewhodgett> for pictures
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