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Rockwell Automation Publication 445L-IN005A-EN-P - May 2018
GuardShield Micro 400 Safety Light Curtains
The safety distance as defined in EN ISO 13855 and EN ISO 13857
depends on:
• Stopping/run-down time of the machine or system. (The
stopping/run-down time is shown in the machine
documentation or must be determined by taking a
measurement.)
• Response time of the protective device, for example,
GuardShield Micro 400 (see
Response Time on page 5
).
• Reach or approach speed.
• Resolution of the light curtain and/or beam separation.
Figure 4 - Safety Distance from the Point of Danger
How to Calculate the Safety Distance S
According to EN ISO 13855 and EN ISO 13857:
First, calculate S using the following formula:
S = 2000 × T + 8 × (d – 14) [mm]
Where…
T = stopping/run-down time of the machine
+ response time of the protective device [s]
d = resolution of the light curtain [mm]
S = safety distance [mm]
The reach/approach speed is already included in the formula.
If the result S is <= 500 mm (19.6 in.), then use the determined value as
the safety distance.
If the result S is > 500 mm (19.6 in.), then recalculate S as follows:
S = 1600 × T + 8 × (d – 14) [mm]
Example:
Stopping/run-down time of the machine = 290 ms
Response time = 30 ms
Resolution of the light curtain = 14 mm (0.55 in.)
T = 290 ms + 30 ms = 320 ms = 0.32 s
S = 2000 × 0.32 + 8 × (14 – 14) = 640 mm (25.1 in.)
S > 500 mm (19.6 in.) therefore:
S = 1600 × 0.32 + 8 × (14 – 14) = 512 mm (20.1 in.)
Minimum Distance from Reflecting Surfaces
The infrared light from the transmitter can be reflected off shiny
surfaces and received by the system receiver. If this condition occurs, it
can result in an object not being detected when it enters the
GuardShield Micro 400 sensing field.
All reflecting surfaces and objects (for example, material bins) must
therefore be at a minimum distance “a” from the protective field of the
system. The minimum distance “a” depends on the distance D between
transmitter and receiver.
Figure 5 - Minimum Distance from Reflecting Surfaces
How to Determine the Minimum Distance from the Reflecting
Surfaces:
-> Determine the distance D [m] transmitter-receiver
-> Read the minimum distance A [mm] from the graph:
Figure 6 - Minimum Distance from Reflecting Surfaces
The effective aperture angle for the GuardShield Micro 400 system is
± 2.5° at a mounting distance of > 3.0 m (9.8 ft). Calculate the
minimum distance to reflective surfaces depending on the distance
between the transmitter and the receiver. Use an aperture angle of
± 2.
5°
or take the appropriate value from the following table:
Formula: a = tan 2.5° x D [mm]
a = minimum distance to reflective surfaces
D = distance between transmitter and receiver
Safety Distance S (D
s
)
Distance to avoid standing behind the safety
curtain ≤ 75 mm (2.95 in.)
Point of
Danger
Protective Field Height
Distance between Transmitter and
Receiver (Range D) [m (ft)]
Minimum Distance
a [mm (in.)]
0…3.0 m (0…9.8 ft)
135 (5.31)
4.0 m (13.1 ft)
175 (6.88)
5.0 m (16.4 ft)
220 (8.66)
Distance D (meters)
D
A
A [mm]
D [m]
50
100
150
200
250
1
2
3
4
5