Siemens PM-E F pm DC24V PROFIsafe Installation And Operating Manual page 38

Wiring and Fitting Modules
4.5 Requirements for Sensors and Actuators
Duration Requirements for Sensor Signals
Observe the following requirements for sensor signals:
• In order to guarantee accurate detection of sensor signals by the F-DI module, you must
• Reliable pulse detection requires an interval between two signal changes (pulse
Reliable detection by the F-DI module
The table below lists the minimum duration of sensor signals for the F-DI module. This
depends on the parameter settings made in
delay.
Table 4- 2
Short-Circuit Test Parameter
Reliable Detection by the Safety Program on the F-CPU
Information about the times required for the reliable detection of sensor signals in the safety
program is available in
description.
Additional Requirements for Actuators
The F-modules test the outputs at regular intervals. To do so, the F-module briefly switches
off the activated outputs. Duration of these test pulses:
● Dark period < 1 ms
Rapid response actuators may briefly drop out during the test. If your process does not
tolerate this, you must use actuators with a sufficient lag (> 1 ms).
If the actuators are operated at voltages greater than 24 VDC (for example, 230 VDC) or if
the actuators switch higher voltages, safe isolation must be ensured between the outputs of
a fail-safe output module and the components carrying a higher voltage (in accordance with
EN 50178).
This is generally the case for relays and contactors. Particular attention must be paid to this
issue for semiconductor switching devices.
38
WARNING
ensure that the sensor signals have a defined minimum duration.
duration) greater than the PROFIsafe monitoring time.
Minimum Duration of Sensor Signals to Allow Correct Detection by F-DI-Module
Deactivated
Activated
"Fail-Safe Modules"
WARNING
STEP 7
for the short-circuit test and the input
Programmed Input Delay
0.5 ms 3 ms
7 ms 9 ms
7 ms 12 ms
Safety Engineering in SIMATIC S7
of the
ET 200S Distributed I/O System - Fail-Safe Modules
Installation and Operating Manual, 08/2008, A5E00103686-07
15 ms
23 ms
37 ms
system