Page 28
User Guide
LSP
HD
Linescanner Head
Example 1
- A greater skew angle
is created when high product
speeds are combined with low scan
frequencies.
Note:
During product width
calculations, the apparent width is
displayed greater than the actual
width.
Example 2
- When high product
speeds are combined with medium
scan frequencies, the skew angle is
reduced when compared to Example 1.
Example 3
- When high product
speeds are combined with high
scan frequencies, the skew angle
is negligible when compared to
Example 1.
The scan skew angle is given by:
e.g. At a scan frequency of 50Hz, a target distance (D) of 2m and product speed of 10m/s .........
θ
= 0.91°
Apparent (measured) product width = actual product width (ignoring edge correction errors)
Cos
θ
6.5 Skew Angle
When a linescanning thermometer is scanning across a moving product travelling along
a line, setting the scan frequency too low may cause the scan line to be excessively
tilted, or 'skewed'. When the product speed is high and the scan frequency is low, the
skew is more apparent, and results in an inaccurate indication of product width.
Product movement
Sc
an
lin
e
Skew angle
θ
θ
θ
−
−
speed
scan
speed
product
TAN
frequency
scan
2
speed
product
TAN
1
1
d
π
θ
Summary of Contents for 0 LAND LSP HD 61
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