4.4.2
Safe series connection
Overview
Several safety switches can be connected in series in a safe series connection. The
type of safe series connection depends on the safety switch variant selected.
The following options are available:
•
Safe series connection with Flexi Loop (with diagnostics)
In a series connection with Flexi Loop, the safety switches are connected to
Flexi Loop nodes. Each Flexi Loop node evaluates a safety switch and sends the
information to the evaluation unit for safety sensors from SICK.
•
Safe series connection with T-connector (without diagnostics)
In a series connection with T-connectors, several safety switches are connected
via T-connectors and connected to the safe evaluation unit. The connected devices
act like a single device.
•
Safe series connection in control cabinet (with diagnostics)
In a series connection in the control cabinet, the safety switches are led to the
control cabinet individually. The OSSDs of the safety switches are connected in
series there and evaluated by the evaluation unit. The Aux outputs can be individu‐
ally connected to the programmable logic controller (PLC).
Safe series connection with T-connectors or in the control cabinet
1
1
1
1
1
2
OSSD1
OSSD2
OSSD1
OSSD2
OSSD1
OSSD2
OSSD1
OSSD2
OSSD1
OSSD2
Figure 9: Switching with 5 safety switches connected in series
1
Safety switch
2
Safe evaluation unit
The voltage drop in the series connection must be checked so that the defined mini‐
mum voltage is still applied to the last safety switch.
For connection cables with a length of 2 m and a cable cross-section of 0.25 mm², the
maximum number of safety switches in connected in series depends on the voltage as
follows:
Table 3: Maximum number of safety switches in a series connection depends on the voltage
Voltage
Connection cables, for ser‐
ies connection
Input voltage at the
last safety switch
Maximum number of
safety switches in ser‐
ies connection
24 V
Length: 2 m
Cable cross-section
•
General: 0.34 mm²
•
Between the safety
switch and series
connection nodes:
0.25 mm²
19.2 V
4
26 V
19.5 V
5
4
PROJECT PLANNING
18
O P E R A T I N G I N S T R U C T I O N S | flexLock
8020562/2022-07-07 | SICK
Subject to change without notice