GE 8021-CE-LH Carrier extender, left hand
Line fault monitoring
In addition to the comprehensive internal
diagnostics the SafetyNet IO Modules can
monitor field wiring for line faults.
Event logging
Data from SafetyNet IO Modules can be
time stamped and stored by the SafetyNet
Controller before being downloaded to the
MOST SOE Data Retrieval Client or a 3rd
party historian package. SafetyNet IO
Module data is time stamped with a
resolution of better than 200ms.
Failsafe Mode
IO Modules will enter Failsafe Mode from
the Running State either due to loss of
communications with the Controller or
because the module has received an
instruction from the Controller to enter the
Failsafe State. In this state:
♦ The Red Fault LED is lit
♦ The IO Module is flagged as unhealthy
to the Controller
♦ All Railbus Write requests are rejected,
except instructions to Reset or to exit the
Failsafe State
♦ Inputs and HART data are read
♦ Outputs are de-energised
♦ Background diagnostics continue and if
a failure is detected, the module will
enter Controlled Shutdown
Controlled Shutdown
A Controlled Shutdown is carried out if a fault
is detected in the Module. In this state it can
communicate the reason for shutdown.
LED’s
A number of LED’s are provided on each IO
Module to provide visual indication of the status
of the Module, its channels and its power supply.
Module ‘Fault’ LED (red)
On - Failsafe
Off - Normal operation
Flashing (equal:mark space ratio) - Cold
start in process, will flash until
communication is established with SafetyNet
Controller.
Blinking (On for a short period, then On
for a longer period – morse code ‘a’) - Fault
state after controlled shutdown
Module ‘Power’ LED (green)
On - Power OK
Off - BFP or Railbus Power Failure
Module ‘Channel’ LED’s
(yellow)
See Individual Module Specifications

Diagnostics
The SafetyNet Analogue Input Module carries
out a number of diagnostic checks to confirm
the accuracy of the measurement reported
and the correct operation of the module.
In addition to the primary measurement, a
second diagnostic measurement is made
using different internal circuitry. The two
values are then compared. The primary
measurement is reported as faulty if it differs
from the diagnostic measurement value by
more than 2%.
Further tests are carried out on internal
supply and references voltages.
If a particular channel fails a test, then that
channel is made inactive. If the failed test
indicates that the Module is not working
correctly, it will enter Controlled Shutdown.
Live maintenance
The field wiring connections to the SafetyNet
Analogue Input Module are classified as
non-incendive and can therefore be live
worked in a Class 1, Division 2 or Zone 2
hazardous area.
(Note the Bussed Field Power connection
must be isolated before the module is
removed or replaced).
Input sampling and filtering
Each input channel is sampled once every
25ms and is filtered by 1st order hardware
and software filters. The software filter can
be disabled or set to a number of different
values according to the filtering
requirements of each channel.
General
The SafetyNet Analog Input Module with
HART provides the interface to 8
channels of 4-20 mA input signals.
The SafetyNet Analogue Input Module is
certified for use in safety-related
applications up to SIL 2. In such
applications the module is used with the
8851-LC-MT SafetyNet Controller and
8811-IO-DC SafetyNet Discrete
Input/Output Module.