Denso BHT-825QW User Manual page 42

When unable to successfully read codes...
Cause
When the light is focused on the printed
Specular surface of the code from directly above,
reflection the BHT may not read the code due to
specular reflection.
Distance from
The code may not be read if it is too close to
code
or too far from the BHT reading window.
Code surface The code may not be read if surface is
curvature extremely curved.
Code surface The code may not be read if its surface is
dirt dirty.
Code reading The code may not be read if the code
window dirt reading window is dirty.
Code reading may be adversely affected
Direct sunlight,
by direct sunlight or the brightness of the
ambient light
surrounding light.
2D Code Handy Terminal
Countermeasure
Change the BHT reading angle and try again.
Move the BHT slowly toward of away from the code and try
again.
Use the display range of the guide marker as a guide. The
valid reading range is approx. 60x38 mm if the reading
distance is 90 mm.
Guide marker
Flatten the label surface and read it again.
Wipe the dirt from the code and try again.
Blow any dust away with an airbrush, and then gently
wipe the reading window with a cotton swab or similar soft
object.
Read the code away from direct sunlight. Adjust the
brightness of the surrounding light when reading indoors.
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