schmersal PSC1 Series Installation Manual page 48

Installation manual
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. 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 EG 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.
HB-37350-810-01-38F-DE PSC1-C-10 Installation manual V1.1.docx
Version: 38F
Page 48 of 177