Siemens SIMATIC ET 200SP System Manual page 305

The discrepancy analysis compares the two input signals of the 1oo2 sensor evaluation in
the fail-safe input module.
Discrepancy time
Configurable time for the → discrepancy analysis. If the discrepancy time is set too high, the
fault detection time and → fault reaction time a re extended unnecessarily. If the discrepancy
time is set too low, availability is decreased unnecessarily since a discrepancy error is
detected when, in reality, no error exists.
Distributed I/O system
System with input and output modules that are configured on a distributed basis, far away
from the CPU controlling them.
DP
Distributed I/O system
→
Earth
Conductive earth whose electrical potential can be set equal to zero at any point.
Equipotential bonding
Electrical connection (potential equalization conductor) that brings the bodies of electrical
equipment and other conductive bodies to the same or almost the same potential, in order to
prevent disruptive or dangerous voltages between these bodies.
Fail-safe modules
ET 200SP modules with integrated safety functions that can be used for safety-related
operation (safety mode).
Fail-safe systems
Fail-safe systems (F-systems) remain in a safe state or immediately assume another safe
state as soon as particular failures occur.
Fault reaction time
The maximum fault reaction time of an F-system defines the interval between the occurrence
of any fault and a safe reaction at all affected fail-safe outputs.
For → F-system overall: The maximum fault reaction time defines the interval between the
occurrence of any fault in any → F-I/O and a safe response at the relevant fail-safe output.
For digital inputs: The maximum fault reaction time defines the interval between the
occurrence of the fault and the safe reaction on the backplane bus.
Distributed I/O system
System Manual, 09/2019, A5E03576849-AJ
Glossary
305