Functional Safety Manual
for the Memosens transmitter Liquiline M CM42 SIL
Version:
Page:
2.0
64
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72
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To store the settings (all parameters) of the used transmitter, you can use a
CopyDAT CY42-C1 (see operating instructions).
10
Overview of modes and current output
Mode of CM42
Current output 1
Current output 2
Classic mode
as configured,
see operating
instructions
as configured,
see operating
instructions
SIL-Mode,
active safe state mode
21.5 mA
21.5 mA
SIL-Mode,
passive safe state mode
>21.5 mA
>21.5 mA
SIL-Mode,
calibration running
Measured pH value
(computed by transmitter)
Measured pH value
(computed by sensor)
SIL-Mode,
SIL measurement mode
Measured pH value
(computed by transmitter)
Measured pH value
(computed by sensor)
System startup,
until classic mode
reached
21.5 mA
21.5 mA
11
PFDavg computation examples
In this chapter we provide some examples to compute the PFD
avg
values of a measuring
chain and the PFD
avg
value after doing proof tests.
Remark
: PFD
avg
(T) = 1/T
0
T
(
DU
t) dt = ½
DU
t (for a1oo1D system, assuming
constant and small failure rate
DU
). Usually PFD
avg
is given without a parameter T,
which means this is the value of PFD
avg
at time T of the mandatory proof test.
11.1
Example to calculate PFD
avg
after a proof test
The aim of a proof test is to show, that the system does not have any dangerous
undetected failures. The proof test coverage denotes the effectiveness of the proof test.
