II - DCE FEL ČVUT v Praze

Parameterization
Default settings
Channel groups
Selectable
measurement
mode
Measuring ranges
for 2-wire and
4-wire transducers
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04
The functions of the analog input module SM 331; AI 4 x 0/4...20 mA are set
with STEP 7 (refer to /231/)
in the user program with SFCs (refer to /235/).
The analog input module features default settings for integration time,
diagnostic interrupts etc. (see Table 3-21). These default settings are valid if
re-parameterization has not been carried out via STEP 7.
The channel group is allocated to each input channel for parameterization of
the analog input module SM 331; AI 4 x 0/4...20 mA. Advantage: You can
specific separate parameters for each channel. Table 3-35 shows the allocation
of channels to channel groups of the analog input module SM 331;
AI 4 x 0/4...20 mA:
Table 3-35 Allocation of analog input channels of the SM 331;
AI 4 x 0/4...20 mA to channel groups
Channel Allocated channel group
Channel 0 Channel group 0
Channel 1 Channel group 1
Channel 2 Channel group 2
Channel 3 Channel group 3
The measurement mode is set with STEP 7 (see Section 3.6.3). The
following types of measurement can be set:
Current measurement
Channel deactivated
Table 3-36 contains all measuring ranges for current measurement with
2-wire and 4-wire transducers. You can set the required measuring ranges
with STEP 7 (see Section 3.6.3).
Table 3-36 Measuring ranges for 2-wire and 4-wire transducers
Selected measurement
mode
Explanation Measuring range
2-wire transducer The digitized analog values are specified in Section 3.1.2 in
Table 3-4 Current measuring range.
4-wire transducer The digitized analog values are specified in Section 3.1.2 in
Table 3-4 Current measuring range.
Wire break check
SIMATIC S7 Ex Analog Modules
from 4 to 20 mA
from 0 to 20 mA
from 4 to 20 mA
Wire break recognition is not possible for the current range 0 to 20 mA.
For the current range from 4 to 20 mA, the input current dropping below
I3.6 mA is interpreted as an wire break and, if enabled, an appropriate
diagnostic interrupt is triggered.
3-65