KROHNE OPTISWITCH 3x00C Transistor SIL EN - Manual (Page 10)

The chronological sequence of PFD
avg
is nearly linear to the
operating time over a period up to 10 years. The above values
apply only to the T
Proof
interval after which a recurring function
test must be carried out.
1 5 10
T
Proof
PFD
avg
1
2
3
4
Fig. 1: Chronological sequence of PFD
avg
(figures see above charts)
1 PFD
avg = 0
2 PFD
avg
after 1 year
3 PFD
avg
after 5 years
4 PFD
avg
after 10 years
Multiple channel architecture
If the measuring system is used in a multiple channel
architecture, the safety-relevant characteristics of the selected
structure of the meas. chain must be calculated specifically for
the selected application according to the above failure rates.
A suitable Common Cause Factor must be taken into account.
Time-dependent proc-
ess of PFD
avg
Specific characteristics
10 OPTISWITCH series 3000 • - transistor (NPN/PNP)
Functional safety
32744
-EN
-080414