Rockwell Automation Allen-Bradley GuardShield 450L-B4FNxYD

Rockwell Automation Publication 450L-UM001D-EN-P - December 2019 101
Installation and Wiring Chapter 6
OSSD Restart Time (from OFF to ON)
The times that are necessary to switch on the OSSDs after clearance of an
interruption of the protective field if automatic reset is as follows.
• Both synchronization beams interrupted before clearance is <210 ms
• Zero or one synchronization beams interrupted before clearance is
<33ms.
Each GuardShield safety light curtain system has two synchronization beams:
one beam is at the bottom and one beam is at the top of the protective field.
Test Pulses
The safety outputs of a GuardShield safety light curtain system use test pulses to
check for OSSD output faults. This process is illustrated graphically in Figure 65
on page 101.
Figure 65 - OSSD Safety Output Test Pulse Characteristic
t
Te st
= 100...125 ms. Actual value depends on stick length. OSSD2 has same timing between pulses as OSSD1, with offset approximately
half of t
Test
.
Pulse is as short as possible, depends on load. 50 ms is typical for resistive load and longer if a capacitive load is used.
The test pulses can lead to the connected device being switched off sporadically if
the device does not filter the test pulses correctly.
OSSD 1
OSSD 2
24V
t
Te st
t
offset
24V