Denso BHT-604Q User Manual page 39

When unable to successfully read barcodes or 2D 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.
The barcode may not be read if it is too
Distance from
close to or too far from the BHT reading
code
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 barcode
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 or away from the code and
try again.
Use the display range of the guide marker as a guide. The
valid reading range is approx. 6×4 cm if the reading
distance is 11 cm.
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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