Siemens SIMATIC ET 200SP Product Information page 19

Additional sensor requirements
General rule: To achieve SIL3/Cat.3/PLe, a single-channel sensor is all you need. However,
to achieve SIL3/Cat.3/PLe with a single-channel sensor, the sensor itself must be
SIL3/Cat.3/PLe-capable; otherwise the sensor must be connected by two channels to
achieve this safety level.
To achieve SIL3/Cat.4/PLe, sensors must be connected by two channels.
In the case of fail-safe input modules, a "0" value is output to the F-CPU after detection of
faults. You therefore need to make sure that the sensors are implemented in such a way as
to ensure the reliable reaction of the safety program when the sensor is in the "0" state.
Example: In its safety program, an EMERGENCY-STOP sensor must achieve the
shutdown of the respective actuator when it is in the "0" state (EMERGENCY-STOP button
pressed).
Duration requirements for sensor signals
Observe the following requirements for sensor signals:
• In order to ensure the correct detection of the sensor signals via fail-safe modules with
• In order for pulses to be detected with certainty, the time between two signal changes
Reliable detection by F-modules with inputs
The minimum duration of sensor signals for F-modules with inputs depends on the
configured input delay, the parameters of the short circuit test of the sensor supplies, and the
configured discrepancy behavior for 1oo2 evaluation. The signal must be greater than the
maximum response time of the configured application. Information on calculating the
maximum response time can be found in section "Response times" of the respective F-
module.
The maximum permitted switching frequency of the sensor signals results from the minimum
duration.
ET 200SP distributed I/O system
Product Information, 07/2013, A5E32288220-AA
4.1 Additional rules and provisions for operation of the ET 200SP with fail-safe modules
WARNING
WARNING
inputs, you need to make sure that the sensor signals are output for a minimum
duration.
(pulse duration) must be greater than the PROFIsafe monitoring time.
Connecting
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