II - DCE FEL ČVUT v Praze

SIMATIC S7 Ex Analog Modules
Diagnostics of
analog input
modules
Faults and
corrective
measures
3-46
Table 3-24 provides an overview of the paramterizable diagnostic messages
of the analog input modules. The enable is set in the “diagnostics” parameter
block (see Section 3.6.3). Diagnostic information is assigned to the
individual channels or the entire module.
Table 3-24 Diagnostic messages of analog input modules SM 331;
AI 8 x TC/4 x RTD, AI 4 x 0 / 4...20 mA and AI 2 x 0/4...20 mA HART
Diagnostic message Effective range
of diagnostics
configurable
Wire break 1) yes
Underrange
Overrange Channel
Reference channel fault 2)
yes,
jointly j y
for all 3 faults
Incorrect parameters in module no
Incorrect parameters in module
Module not parameterized
No external auxiliary voltage 3)
No internal auxiliary voltage 3)
Fuse blown 3)
Watchdog triggered Module no
EPROM error 4)
RAM error 4)
CPU error 4)
ADU error 4)
Hardware interrupt lost
1) If wire break diagnostics is enabled, the modules AI 4 x 0 / 4...20 mA and
AI 2 x 0/4...20 mA output the wire break message for the connected 2-wire transducer
(4...20 mA) if the input current drops below a value of I3.6 mA (wire break limits
in accordance with NAMUR). For the digital measured value, see Figure 3-4.
In the case of the module AI 8 x TC/4 x RTD the line is checked by connecting a test
current if wire break diagnostics is enabled. The wire break message is only
deactivated (hysteresis), when the input current rises above 3.8 mA again.
2) Only for thermocouples with external compensation and compensation fault.
3) Only for AI 4 x 0 / 4...20 mA and AI 2 x 0/4...20 mA HART with 24 volt supply from
L+.
4) The tests are conducted during start-up and on-line.
Table 3-25 provides a list of possible causes and corresponding corrective
measures for individual diagnostic messages.
Bear in mind that, in order to detect faults which are indicated by means of
configurable diagnostic messages, the module must also be parameterized
accordingly.
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04