II - DCE FEL ČVUT v Praze

Table 3-25 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 their possible causes and corrective measures
Diagnostic message Possible fault cause Corrective measures
Wire break Break in line between module and sensor Connect line
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04
Channel not connected (open) Deactivate channel group (”Measurement
mode parameter)
Measuring range underflow Input value below underflow range, fault
possibly caused by:
on AI 8 x TC/4 x RTD – Incorrect type of thermocouple
– Sensor connected with reversed
polarity
– incorrect measuring range selected
on AI 4 x 0 / 4...20 mA – Module does not signal
measuring range underflow
– Sensor connected with reversed
polarity;
(a digitized value is output for
0 mA)
– Check type of thermocouple
– Check connection terminals
– Parameterize different measuring range
Measuring range overflow Input value exceeds overflow range Parameterize different measuring range
Reference channel fault Measuring channel has different type of
sensor parameterized as reference
channel
Incorrect parameters in
module
Parameterize different type of sensor
Fault in reference channel (e.g. wire Eliminate fault in reference channel
break) values of all measuring channels
set to 7FFFH
Module supplied with invalid parameters Check parameterization of module and
re-load valid parameters
Module not parameterized Module not supplied with parameters Include module in parameterization
No external auxiliary voltage No module supply voltage L+ Provide L+ supply
No internal auxiliar y voltage No module supply voltage L+ Provide L+ supply
Module-internal fuse defective Replace module
Fuse blown Module-internal fuse defective Replace module
Time watchdog tripped In part, high electromagnetic interference Eliminate interference sources
Module defective Replace module
EPROM error
In part, high electromagnetic interference Eliminate interference sources and switch
RAM error
CPU supply voltage OFF/ON
CPU error
ADU error Module defective Replace module
Hardware interrupt lost Successive hardware interrupts (limits
exceeded, end of cycle interrupt) occur
faster than the CPU can process them
SIMATIC S7 Ex Analog Modules
Change interrupt processing in CPU and
reparameterize module if necessary
3-47