54733-10BA2L
1 – 98 02.2017
7 Functional Safety Volume 1
• Detector code "1" has to be used for the following types of
detectors: when count rates of less than 1000 cps may occur
within the measuring range. In the other case detector code "0"
can be used.
– LB 480-11 (CrystalSENS 50/50)
– LB 480-12 (CrystalSENS 50/50 with water cooling)
• The error current (Loop Alarm Type) has following setup
options:
– High: >21mA
–Low: <3.6mA
7.5.3 Assumptions
The evaluation of the measuring device according to functional
safety aspects is based on the following assumptions:
• The failure rates are constant over the lifetime.
• The environmental conditions correspond to an average indus-
trial environment.
• The repair time (replacement of the measuring system) after
an interference immune error is 72 hours. (MTTR
1
= 72h).
• The maximum operating time is limited by the average count
rate and the scintillator used:
• A temperature compensation can be used for a density mea-
surement.
The following error cases are not considered:
• Closing or removing the source
• Failure rates of external power supplies
• Multiple errors
1. MTTR = Mean Time To Repair
maximum operating time
average count
rate
CrystalSENS
(Point detectors
with NaI crystal)
UniSENS (rod detectors)
SuperSENS
TowerSENS
40000 cps 10 years 10 years
80000 cps 5 years 10 years
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