Rockwell Automation T7419 User Manual
ICS Regent+Plus
®
PD-7032
Fire Detector Input Modules
(T7419)
Issue 1,
Fire detector input modules provide interfaces for 16 fire
detector inputs such as smoke detectors, flame detectors,
temperature detectors, and manual alarm call points. Eac
module performs line monitoring on the field wiring
connections and automatic testing of the module’s input
electronics. Input and line status are reported back to the
controller for use in application program logic.
March, 06
h
Features
·
Sixteen input points.
·
Individual channel Reset control output to reset latched fire
detectors.
·
Fault tolerant operation when redundant modules and sensors
are configured.
·
Hot-replaceable.
•
Complete, automatic testing of all input circuits.
•
Automatic line monitoring detects open and short field wiring
faults.
·
Individual front panel indicators on each module show the
module’s fault/active and power status, as well as input status
indicators for each point.
·
2500 volt minimum electrical isolation between field and logic
circuits.
·
TÜV certified, Risk Class 5.
The input module circuits are thoroughly tested, providing a
fail-safe interface for safety critical inputs. For fault tolerant
configurations, two fire detector input modules are used to
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Fire Detector Input Modules
connect to redundant field sensors. In this dual module
configuration, a failed module can be removed and replaced
without affecting system operation.
The module requires connection to a field power supply
voltage, ranging from 15 to 40 VDC. This supply voltage is
internally regulated to power the fire detector field input
circuits.
(T7419)
Module Operation
A block diagram of a typical fire detector input module is
shown in Figure 1.
2
Figure 1. Block Diagram of Fire Detector Input Module.
A field power supply is connected to the fire detector input
module. The field power is internally regulated to 23.5 Vdc to
power the fire detector field inputs. Each input is b
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iased to
Fire Detector Input Modules
(T7419)
this regulated voltage with an internal resistor. Externally
each input connects to an associated field sensor and a line
terminator. The module monitors the input voltage to detect
a variety of input states. The module can discriminate and
report sensor tripped, sensor healthy, line open and line
shorted conditions. Additional circuits allow the module to
reset a latched fire detector by removing power from the
associated input circuit.
Internally the module generates a reference voltage that
is
compared to the field inputs. The comparator generates an on
or off state depending on which voltage is greater. The field
side FPGA controls and monitors the reference voltage signal
and reads the status of all 16 input comparators. This
information is stored and sent through optical isolation to the
logic-side FPGA. This FPGA interfaces the input date to the
I/O safetybus and drives the module’s front panel indicators.
Testing and Diagnostics
Standard I/O Module Testing
The processor modules send triplicated read data requests to
the input module over the I/O Safetybus. The processors’
addressing data and data read requests are voted by the
module (preventing I/O Safetybus failures upstream from the
module from affecting its ability to be read). The voted result
is then passed to the I/O bus interface logic.
After receiving the voted data read request, the I/O bus
interface logic sends its input data to the module’s three bus
drivers. Each of the three bus drivers is independently
controlled —
propagated into the rest of the system.
pre
venting failures in a single driver from being
PD-7032
Mar-06
The bus drivers then move the data onto the I/O Safetybus
which, in turn, passes it to the processors.
Each module’s voter circuits are periodically tested by the
processor modules. Discrepant data are sent through one of
three legs of the I/O Safetybus to determine whether the
module’s voter is able to outvote the incorrect data. A failure
to return the correct majority-voted result to the processors
produces an I/O mo
modules and a module fault indication at the I/O module.
3
dule error indication at the processor
Fire Detector Input Modules
Each type of module has a unique identification code that is
read by the controller. This code lets the controller know
which type of module is installed in each I/O chassis slot and
address that module and its points specifically. The processor
modules periodically check each module’s identification code
to determine whether the type of module installed matches
type of module indicated in the I/O configuration
loaded when the system was started. If a module is removed,
or is replaced with a module of a different type, the processor
modules will indicate I/O module errors.
Loopback logic tests periodically write data to the module and
then read it back to determine whether the module’s I/O bus
interface logic is functioning correctly.
(T7419)
that was
Input Circuit Testing
The field interface circuits of the fire detector input module
are completely tested to detect stuck-on or stuck-off input
circuit faults and identify input wiring open and short circuits.
The automatic execution and evaluation of the input testing
is controlled by the triplicated Regent processor modules.
During normal operations, the internal reference voltage is
set to three levels and the comparator output is read. These
three reference voltage levels represent thresholds that
determine whether the input signal is in alarm or healthy and
if the field wiring is open circuit or short circuit. The logic-side
FPGA determines input status and line fau
lt status based on
the comparator data for the three voltage levels. The FPGA
data is provided to the I/O processors for application
processing.
On a background basis, the I/O processors test the input
circuit comparators and logic circuits for stuck-on and stuck
off failure modes. During testing the D/A converter generates
two reference voltages outside the normal operating range of
the field input voltages to test that the comparator output can
turn-off and turn-on. The I/O processors read the resultin
g
input status, line fault status, and reference voltage readings
for the test cycle to determine if there are faults in the input
circuits or the common data paths.
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Fire Detector Input Modules
Note:
(T7419)
If the I/O processors detect a faulted input circuit, an I/O
module fault is indicated at the processor modules and the
Fault LED on the face of the input module is turned on.
Input Circuit Test Interval
The Regent processor modules schedule testing of the input
circuits on a background basis. The test interval for these
circuits may range fro
m a few seconds to several minutes,
depending on the application program scan time and the size
of the I/O configuration. The equation below can be used to
estimate the test interval for monitored digital inputs.
TI = 172 * IOU
where:
TI
IOU
TSCAN
=
=
QTY
=
* TSCAN + 2
QTY
Test interval, seconds
Quantity of I/O Units in the system (1 to 16)
The application program scan time, seconds
For example, for a system with 8 I/O units and an application
scan time of 60 milliseconds, the test interval would be:
TI = 17
2 * IOU
TI = 84.6 seconds
* TSCAN + 2 = 172 * 8 * 0.060 + 2
QTY
In this system, all of the fire detector input modules would be
tested for stuck-on and stuck-off faults approximately every 85
seconds. This test interval can be used in reliability and
availability calculations to select the fault tolerant input
configuration that meet the application’s safety requirements.
PD-7032
Mar-06
Due to I/O processor fault filtering algorithms, it may take up
to four test intervals to report a failed input module as
permanent fault
Front Panel Indicators
a
Figure 2 shows the physical features of the fire detector input
modules. The front panel of each module contains fault/active
and power indicators for the module as well as input status
indicators for each channel.
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Fire Detector Input Modules
(T7419)
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Figure 2. Fire Detector Input Module.
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