MTBF Mean Time Between Failures
MTTF Mean Time To Failure
Muting Muting is the intended suppression of the safety function. This is required, e.g. when
transporting the material into the danger zone.
NC Break contact. Normally-Closed contacts disconnect the circuit when the relay is acti-
vated; the circuit is connected when the relay is inactive.
NO Make contact. Normally-Open contacts connect the circuit when the relay is activated; the
circuit is disconnected when the relay is inactive.
OEM Original Equipment Manufacturer
Passivation The passivation is the special state of Safety I/O modules which leads to the delivery of
safe substitute values, which are ‘0’ values in AC500-S, to the Safety CPU.
PELV Protective Extra Low Voltage
PES Programmable Electronic System (see IEC 61508 ed. 2)
PFD Probability of Failure on Demand
PFH Probability of Failure per Hour
PL Performance Level according to ISO 13849
PLC Programmable Logic Controller
POU Program Organization Unit
PROFIsafe Safety-related bus profile of PROFIBUS DP/PA and PROFINET IO for communication
between the safety program and the Safety I/O in the Safety system
Proof Test
Interval
The proof test is a periodic test performed to detect failures in a safety-related system so
that, if necessary, the system can be restored as close as possible to its previous new
state. The time period between these tests is the proof test interval.
PS Programming System
RAM Random Access Memory
Reintegration It is the process of switching from substitute values “0” to the process data.
Safety variable It is a variable used to implement a safety function in a safety-related system
SCA Safety Code Analysis – ABB software tool to automatically check CoDeSys safety pro-
gramming rules
SD card Secure Digital Memory Card
SELV Safety Extra Low Voltage
SFRT Safety Function Response Time
SIL Safety Integrity Level (IEC 61508 ed. 2)
ST Structured Text (IEC 61131 Programming Language)
TÜV Technischer Überwachungs-Verein (Technical Inspection Association)
Introduction
Definitions, expressions, abbreviations
30.03.2017AC500-S12
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