optris Top-down GIS, Operator'S Manual

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5.3 Hardening of glass sheets
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Temperature has a direct influence on glass quality
•
Testing for the heating profile (temperature distribution)
Linescan function (line scanning) with PI camera from above and reference measurement with pyrometer from
below.
Direct effects: Defective or inhomogeneous surfaces can be detected by the measurement.
Tempering: Change of the heating/cooling degree depending on the temperature distribution
5.4 Referencing from below
Referencing from below is necessary because Low-E glass is used in a glass tempering system. Low-E
coatings minimize IR radiation through glass, but not the thermal effect of visible light. Low-E glass has a
coated side (top) and an uncoated side (bottom).
2 reasons for referencing:
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The coated side on the upper side has a low emissivity. Therefore it is more difficult to measure and
leads to inaccurate results