16
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Chapter 2 Measurement
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CAUTIO
If the instrument is exposed to direct sunlight for a
long time, it may be deformed. When using it
outdoors, as far as possible keep in the shade.
Even if not directed toward the sun, the scale absorbs
heat rapidly.
Brightness and exposure
of refreshing light
Length of time scale remains
legible in the dark
(at approx. 15 cm from the eye
Average living room lighting
at night (approx. 200 lx, for
5 minutes)
5 minutes approx.
In the office (approx. 1000
lx, for minimum 30 seconds)
10 minutes approx.
Daylight outdoors (approx.
minimum 10,000 lx, for
minimum 30 seconds)
15 minutes approx.
.6 Luminous Scales
The 3452 scales are marked with a
phosphorescent paint. Once this is refreshed
by exposure to light, it remains luminous for
a while, allowing measurement in a dark
place.
The following table gives a guideline to the
length of time the scale remains legible in the
dark for different refreshing conditions.