Additional Information On Sm 331; Ai 8 X 12 Bit; This Optimizes - Siemens SIMATIC Manual

Analog modules
6.7 Analog input module SM 331; AI 8 x 12 bit;(6ES7331-7KF02-0AB0)
6.7.4

Additional information on SM 331; AI 8 x 12 Bit

Unused channels
As certain programmed inputs may remain unused due to the channel group configuration,
make allowances for the special features of these inputs outlined below in order to be able to
use the diagnostics functions at these used channels:
● Voltage measurement (except 1 V to 5V) and for thermocouples: Short-circuit unused
channels and connect these with M
analog input module. Set the "disabled" value at the "measurement type" parameter for
unused channels. This setting reduces module cycle times. Also short-circuit the COMP
input if this is not used.
● Measuring range 1 V to 5 V: wire the used and unused inputs of the same channel group
in parallel.
● Current measurement, 2-wire transducer: There are two options of wiring the channel
circuit.
a) Open unused input; channel group diagnostics disabled. If you were to enable
diagnostics, the analog module would trigger a single diagnostic interrupt, and light up its
SF LED.
b) Loading the unused input using a 1.5 kΩ to 3.3 kΩ resistor. This allows you to enable
diagnostics for this channel group.
● Current measurement 4 mA to 20 mA, 4-wire transducer: wire the unused inputs of the
same channel group in series.
All channels deactivated
If you disable all input channels of the module and enable diagnostics at the parameters of
SM 331; AI 8 x 12 Bit, the module does not report "external auxiliary voltage missing."
Line continuity check for the 4 mA to 20 mA measuring range
If you configured a measuring range of 4 mA to 20 mA, and enabled the line continuity
check, the analog input module logs a wire-break event to diagnostics data when the current
drops below 3.6 mA.
The module also triggers a diagnostics interrupt if this function is enabled in the program.
A wire break can only be signaled by means of the lit SF LED and the diagnostic bytes must
be evaluated in the user program if diagnostics interrupts are disabled.
If you configured a measuring range of 4 mA to 20 mA, disabled the line continuity check,
and enabled diagnostic interrupts, the module triggers a diagnostic interrupt when the
underflow value is reached.
Line continuity check
The line continuity check is designed only for temperature measurements (thermocouples
and thermoresistors.)
See also
Representation of the values for analog input channels (Page 262)
366
. This optimizes interference immunity of the
ANA
S7-300 Module data
Manual, 06/2017, A5E00105505-AJ