schmersal PSC1-C-10 Series Installation Manual page 46

Installation manual
On the usage of a single-channel sensor with test pulses, one connection is connected to the test pulse
output T0 or T1 of the PSC1. The pulse assignment must then also be carried out in SafePLC2.
The usage of a single-channel sensor with test pulses detects:
Short-circuit to the supply voltage DC 24 V
Short-circuit to DC 0 V
Cable break (interruption of power is safe state!)
Caution is required, on the other hand, if there is a cable short-circuit between the two connections
for the sensor, as this will not be detected! A short-circuit between T0 and I00 is also not detected.
Due to the single-channel character of the switching element / sensor, a fault exclusion is required for
its failure. This exclusion is allowed on the usage of positively opening switches with correct positive
actuation.
The series connection of 2 switching elements with corresponding fault exclusion for a double fault is
the same as this application (occurrence of two faults at the same time). This could represent, e.g. the
safety outputs on an electronic monitoring device (light curtain, safety mat) with internal dual-channel
shutdown.
On the usage of a suitable switching element and careful wiring of the sensor, PL d according to EN ISO
13849-1 can be achieved. In special cases, i.e. in conjunction with suitable switching elements and
permissible fault exclusions, PL e according to EN ISO 13849-1 can be achieved.
Safety instructions:
•
PL d or higher according to EN ISO 13849-1 is achieved if a short-circuit between the input and
related pulse output as well as a short-circuit between the sensor connections can be
excluded. Here it is to be noted that in the event of a fault, the switch must be positive
opening according to EN 60947-5-1. In addition, the sensor must be triggered at regular
intervals and the safety function demanded. Fault exclusions can be obtained as per EN ISO
13849-2 Table D8. On the single-channel usage of the inputs, the safety level that can be
achieved is limited to SIL 2 or PL d, if there is no demand for the safety function at regular
intervals.
•
The connection in series of 2 switch elements with fault exclusion for a double fault requires a
check for suitability according to the safety level required for this element. Reference is made
to the applicable stipulation in the EC Machinery directive 2006/42/EC.
•
With single-channel sensors, in principle the safety-related usage of the inputs is only
intended in conjunction with the pulse outputs.
PSC1-C-10 Installation manual V2.6
Version: 57E
Page 46 of 173