Allen-Bradley GuardPLC 1753, Справочник по безопасности

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112 Publication 1753-RM002C-EN-P - September 2008
Appendix B Use in Central Fire Alarm Systems
For the application, the resistance of R
EOL
, R
L
and R
shunt
should be
calculated based on the sensors used and the number of sensors per
alarm loop. The required data is contained in the relevant
specifications from the sensor manufacturer.
The alarm outputs, used for activating lamps, sirens, and horns, are
operated using the open-circuit principle. These outputs must be
monitored for line breaks and short-circuits. This can be accomplished
by feeding back the output signals directly from the actuator to the
inputs.
The current in the actuator should be monitored via an analog input
with an appropriate shunt. A series connection of a zener diode
protects the input over-voltage in case of a short-circuit.
For explicit line break monitoring (at de-energized outputs DO), a
transmitter supply to the analog inputs is necessary, as shown below.
For more information on line monitoring, refer to the GuardPLC
Controller Systems User Manual, publication number 1753-UM001.
Example for line break and short-circuit monitoring of digital outputs
Visual display systems, indicator light panels, LED displays,
alphanumeric displays, and audible alarms, can all be controlled by
the user program.
The routing of fault signals via input and output modules or to routing
equipment must be accomplished by using the closed-circuit current
principle.
Digital
Output
L-
R
shunt
Actuator
R
series
R
diode
area for monitoring of line break and short-circuit
protective circuit, in case of short-circuit
Field Terminal
Field Terminal
26.4V
12V
L-
Ix