Advantech IDK-1115R-40XGC2E User Manual page 36

Note 5 Measurement Setup:
The LCD module should be stabilized at given temperature for 20 minutes to
avoid abrupt temperature change during measuring. In order to stabilize the
luminance, the measurement should be executed after lighting Backlight for
20 minutes in a windless room.
Note 6 Definition of White Variation (δW):
Measure the luminance of gray level 255 at 5 points
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