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Safety function
Safe state
Fault signals in case of
malfunction
Instructions and restric-
tions
3
Planning
3.1
Safety function
To monitor a limit level, the sensor detects via the conditions "Vibrat-
ing element uncovered" or "Vibrating element covered" a limiting
value defined by the mounting location.
The detected status is signalled on the output with "Relay contact
open" or "Relay contact closed".
3.2
Safe state
The safe state of the output signal is independent of the mode ad-
justed on the sensor.
For the safety function, only the NO contact may be used (idle current
principle)!
Both NO contact must be connected in series!
Mode
Vibrating element
Relay
Relay outputs:
•
NO contacts open
3.3
Prerequisites for operation
•
The measuring system should be used appropriately taking pres-
sure, temperature, density and chemical properties of the medium
into account. The application-specific limits must be observed.
•
The specifications according to the operating instructions manual,
particularly the current load on the output circuits, must be kept
within the specified limits
•
To avoid a fusing of the relay contacts, these must be protected by
an external fuse that triggers at 60 % of the max. contact current
load.
•
When used as dry run protection, buildup on the vibrating system
should be avoided (probably shorter proof test intervals will be
necessary)
•
The instructions in chapter "Safety-related characteristics", para-
graph "Supplementary information" must be noted
•
All parts of the measuring chain must correspond to the planned
"Safety Integrity Level (SIL)"
SITRANS LVL200H - Safety Manual
Overflow protection
Mode max.
covered
NO contact open
(currentless)
Dry run protection
Mode min.
uncovered
NO contact open
(currentless)
5
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