7
Connection
Examples
EDBC250SIO | 2.0
231
7.6
Connecting Two Actuators with Internal GND Reference
The wiring example illustrates how two outputs of the safe I/O module are used to actuate a
safety function. Switch contacts K1 and K2
both affect the safety function together.
Using the SOX terminals of the outputs allows
the actuator to separate from the GND con-
nection and, thus, change to its safe state
when external power is supplied to an cross-
faults affect the actuator (contact SOX+).
Whereas you may set up this circuit without
the SOX- terminals, you must ensure that ex-
ternal power and cross-faults are excluded if
you do.
In order to monitor the relay states, you must
connect the positively drive n.c. contacts of
K1 and K2 to safe digital inputs. Set the safe
PLC to analyse the values returned and, thus,
the states of the switching devices.
Safety ratings of two-channel actuators
The safety ratings listed in the table below reflect the maximum values a two-channel safety
function may achieve when using two outputs of the safe I/O module. They solely apply to the
part of the safety function covered by the safe I/O module. All components involved in the
safety function must be taken into account in order to assess whether the desired safety rat-
ings are achieved. The quality of the safe actuator is of crucial importance with particular re-
gard to the safety function of analysing a two-channel actuator. Only use approved actuators
in due consideration of their B10d value. The safety assessment of the safety function must
also consider the safety ratings of the safe PLC used in the application.
Safety ratings of applications using two outputs for a safety function
Highest safety integrity level to EN 62061:2010
SIL3
Highest safety integrity level to IEC 61508:2010
SIL3
Category and highest performance level to EN ISO 13849-1:2015
Cat. 4/PL e
Hardware fault tolerance (HFT) in two-channel application
(IEC 61508:2010/EN)
1
(a fault of the application cannot cause the safe-
guard to fail)
