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EN
3.3.2 Sample Calculations
Example 1: Light curtain with a safety field height of 764 mm, vertical installation, 14 mm resolution
Assuming:
light curtain response time SG4-14Ix075C1
t1 = 26 ms
machine over-travel time
t2 = 20 ms
light curtain resolution
d = 14 mm
approach speed
K = 2000 mm or 1600 mm/s
Safety clearance S =
K × (t1 + t2) + C, since light curtain resolution is < 40 mm is C = 8 × (d – 14 mm)
Safety clearance S =
K × (t1 + t2) + 8 × (d – 14 mm) = 2000 mm/s × (0,026 s + 0,02 s) + 8 × (14 mm – 14 mm)
= 92 mm
Safety clearance S =
K × (t1 + t2) + 8 × (d – 14 mm) = 1600 mm/s × (0,026 s + 0,02 s) + 8 × (14 mm – 14 mm)
= 73,6 mm
A safety clearance of 92 mm must be selected. Due to the fact that safety clearance is less than 500 mm,
K = 2000 mm/s must be used for calculation purposes.
However, since both calculated safety clearances S are less than 100 mm, a minimum clearance of
S = 100 mm applies
This example demonstrates that calculations must always be performed using both approach speeds!
Example 2: Light curtain with a safety field height of 764 mm, horizontal installation, 30 mm resolution
Assuming:
light curtain response time SG4-30Ix075C1 t1 = 12 ms
machine over-travel time
t2 = 20 ms
light curtain resolution
d = 30 mm (electronically reduced to 42 mm)
approach speed
K = 1600 mm/s
installation
height
500
mm
Safety clearance S =
K × (t1 + t2) + C, height is decisive regarding C in this case:
C = 1200 – 0,4 × H
Safety clearance S =
K × (t1 + t2) + (1200 – 0,4 × 500 mm)
= 1600 mm/s × (0,012 s + 0,02 s) + (1200 mm – 0,4 × 500 mm) = 1051,2 mm
The following points must be observed:
1. Calculated resulting resolution is independent of light curtain resolution:
max. resulting resolution: d = H/15 – 50 mm = 500 mm/15 + 50 mm = 83 mm
2. A resolution of less than 50 mm cannot be implemented with this setup: min. height = 15 × (d – 50 mm)
