Siemens Simantic ET200SP System Manual page 296

Glossary
Discrepancy analysis
The discrepancy analysis for equivalence/non-equivalence is used for fail-safe applications
to prevent errors from time differences between two signals for the same function. The
discrepancy analysis is initiated when different levels are detected in two associated input
signals (when testing for non-equivalence: the same levels). A check is performed to
determine whether the difference (for nonequivalence testing: the same levels) has
disappeared after an assignable time period, the so-called discrepancy time. If not, this
means that a discrepancy error exists.
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.
Explosion protection
Prerequisite for using electrical equipment in hazardous areas conforming to DIN EN 50014
(VDE 0170/0171). For explosion protection, you must ensure that equipment which may
generate explosive arcs (plasma) during operation is enclosed in a flameproof casing. This
means that, although the potentially explosive mixture could penetrate the enclosure, if an
explosion were to occur inside it then no explosive flame could escape.
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Distributed I/O system
System Manual, 12/2016, A5E03576849-AG