Rockwell Automation T3404 ICS Regent AC Digital Input Module 110 VAC - Manual (Page 13)

(T3404) AC Digital Input Module
P D - 6 0 1 3 M a r - 0 6
13
In this illustration, VOTE_A_NAME, VOTE_B_NAME, and
VOTE_C_NAME represent the three digital inputs to be two-
out-of-three voted. ERROR_A_NAME, ERROR_B_NAME
and ERROR_C_NAME are the error bits for the digital
inputs. RESULT_NAME is the result of the voter instruction.
The field Msec is the time, in milliseconds, an input can be
incorrect before signaling an error. RESET_NAME is the
reset bit used to reset the latched error bits.
The voter instruction can be used to vote digital input points
or entire digital input modules. When voting digital input
modules, the tag names VOTE_A_NAME, VOTE_B_NAME,
and VOTE_C_NAME would be the names of the digital input
modules and RESULT_NAME would be a shared variable
register. After voting the modules, a block move instruction
should be used to move the contents of the register
RESULT_NAME into individual shared variable control
relays. Refer to the W
INTERPRET Help files for more
information about the block move instruction and shared
variable definitions.
Maintenance
No periodic maintenance or calibration is required for the AC
digital input module. There are no user replaceable parts
inside the module. In safety critical input applications, the
inputs should be dynamically transitioned at a period not
greater than six months.
Safety Considerations
The AC voltage digital input module is TÜV certified as non-
interfering and when properly configured is also certified for
Risk Class 5 safety critical inputs. Safety critical
configurations include 2oo3 and 1oo2 voting methods.
In safety critical input applications using a single sensor, it is
important that the sensor failure modes be predictable and
well understood, so there is little probability of a failed sensor
not responding to a critical process condition. In such a
configuration, it is important that the sensor be tested