Analog modules
6.3 Analog input module SM 331; AI 8 x 16 Bit; (6ES7331-7NF00-0AB0)
S7-300 Automation System Module data
Manual, 08/2006, A5E00105505-04
6-15
6.3.3 Additional information on SM 331; AI 8 x 16 bit
Unused channels
For unused channels, set the "disabled" instruction at the "measuring method" parameter.
This reduces the module's cycle time.
Certain inputs of the channel group configuration may remain unused. To be able to use
diagnostic functions at the used channels, note the special features of those inputs outlined
below:
● Measuring range 1 V to 5 V: wire the used and unused inputs of the same channel group
in parallel.
● Current measurement, 4 to 20 mA: wire the unused inputs of the same channel group in
series. Connect a shunt resistor to each programmed and unused channel.
● Other measuring ranges:Short-circuit the plus and minus inputs of the channel.
Wirebreak monitoring
The wire-break check is available for the 1 V to 5 V range, and for the 4 mA to 20 mA range.
Applicable to both measuring ranges:
When the wire-break check is enabled, the module logs the wire-break in its diagnostics
buffer when the current drops below 3.6 mA (0.9 V.)
The module also triggers a diagnostic interrupt if you enabled diagnostics interrupts in the
program.
The lit SF LED is otherwise the only indication of the wire-break, and you must evaluate the
diagnostic bytes in the user program.
When wire-break check is disabled, and diagnostic interrupts are enabled, the module
triggers a diagnostic interrupt when the underflow value is reached.
Special features in programming high and low limits
The programmable limits (hardware interrupt triggers) of SM 331; AI 8 x 16 Bit differ from the
range of value shown in the
Overview of parameters of SM 331; AI 8 x 16 Bit.
table.
Reason: in certain situations, the calculation methods of the module software used to
evaluate the process tags do not return values up to 32511. The process value triggering a
hardware interrupt at underflow or overflow limits is based on the calibration factors of the
relevant channel, and may vary between the low limits shown in the Table below and 32511
(7EFF
H
).
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