II - DCE FEL ČVUT v Praze

3.6.6 Characteristics of Analog Modules
Introduction
Influence of
supply voltage and
operating status
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04
Described in this section:
Dependency of the analog input and output values on the supply voltage
of the analog module and the operating status of the CPU.
Characteristics of the analog modules depending on the position of the
analog values in the relevant value range.
Influence of faults on the analog modules.
The input and output values of the analog modules are dependent on the
supply voltage of the analog module and on the operating status of the CPU.
Table 3-28 provides an overview of these dependencies.
Table 3-28 Dependencies of analog input/output values on the CPU operating status and the supply voltage L +
CPU operating
status
POWER
ON
POWER
ON
POWER
OFF
Supply voltage
L+ at analog
module
Input value of
analog input modules
RUN L + applied Process value CPU value
7FFFH up to first conversion after
switching on or after module
parameterization has been
completed
No L + Overflow value 1) 0 mA
STOP L + applied Process value Default/last value
7FFFH up to first conversion after
switching on or after module
parameterization has been
completed
No L + Overflow value 1) 0 mA
– L + applied – 0 mA
No L + – 0 mA
1) only applies to SM 331; AI 8xTC/4xRTD as no L+ supply voltage is required.
SIMATIC S7 Ex Analog Modules
Output value of
analog output module
Up to first conversion ...
after switch-on has been
completed if signal of 0 mA is
output.
after parameterization has
been completed, previous value
is output.
at 0...20 mA: 0 mA default
at 4...20 mA: 4 mA default
Failure of the L+ supply voltage for the analog modules is always indicated
by the group fault LED on the module and additionally entered in diagnostics.
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