Siemens SITRANS P DS III - Key Glossary Terms

SITRANS P DS III with PROFIBUS PA
Operating Instructions, 06/2013, A5E00053276-07
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Glossary
Coupler
connects the DP and PA segments in PROFIBUS. It has a fixed transmission speed. The
transmission speed is 45.45 kbps (DP) to 31.25 kbps (PA).
Dangerous failure
Failure with the potential to switch a safety-instrumented system to a hazardous or non-
functioning safety status.
Diameter nominal
The diameter nominal is specified according to DIN EN ISO 6708 by the term DN followed by
a dimensionless number approximating the inner diameter in millimeters. According to DIN
2440 (medium-weight threaded pipe), a DN 50 pipe, for example, identifies a pipe with an
outer diameter of 60.3 mm and a wall thickness of 3.65 mm (inner diameter therefore 53
mm).
EEPROM
EEPROM (Electrically Erasable Programmable Read-Only Memory) is a non-volatile,
electronic memory chip.
EEPROM are often used when individual data bytes change over long intervals and need to
be stored and retained if there is a network failure, for example configuration data or
operating hours counters.
Failure/Fault
Failure:
A resource is no longer capable of executing a required function.
Fault:
Undesired state of a resource indicated by the incapability of executing a required function.
Fault
→ Failure/Fault
Fault tolerance
Fault tolerance N means that a device can execute the intended task even when N faults
exist. The device fails to execute the intended function in the case of N+1 faults.