Specifications

Engineering Standard –NSW
Signalling SMS 02
Cerberus Level Crossing Monitor Equipment
March 2005 Version 1.2 © Australian Rail Track Corporation Page 31 of 118
This document is uncontrolled when printed.
3.2.4.4 Troubleshooting
The Version 1.0 ADC board will fail if reverse polarity is applied to the
level crossing monitor input terminals. The failure will be indicated by
the level crossing monitor giving a system fault and battery low
indication. The application of reverse polarity will cause one of the PC
tracks to burn open circuit. If a jumper wire is soldered in place of the
burnt out track it is most likely that the board will be useable. This
problem was rectified for the ADC boards V2.0 or later which are
supplied with the Version 3.0 level crossing monitors.
By looking at the analogue inputs it is possible to see if the ADC board
is supplying valid readings. If the all of the inputs read zero then maybe
the ribbon cable is not connected or the board has failed. The board is
susceptible to lightning damage and should be checked carefully if the
level crossing monitor has failed after a lightning strike or surge. If the
inputs read full voltage with no current sensors connected then the
ADC board is faulty and should be replaced.
Failure of the ADC board is indicated by the battery voltage to
analogue input 1 reading zero. This will result in a system fault being
displayed. Individual failures of the other inputs 2-8 is rare but each
input can be checked by monitoring the analogue inputs (by viewing I/O
inputs) and connecting 5 volts to each input and confirming that the
A/D reading is close to 255.
The ADC board will also fail if the internal +12V rail fails or goes low
voltage. The ADC board uses this +12VDC rail to generate a voltage
reference. If the +12V rail fails than the ADC will read zero on all of it’s
inputs. (Note: it is possible for a failed current sensor or faulty wiring to
the sensor supply terminals 1-11 to fail the internal +12V rail and
therefore fail the ADC board.
3.2.4.5 Replacement Procedure
Open lid of the Level Crossing Monitor. Turn off the power. Unplug the
cable. Remove the screw and unplug the ADC module from the
SCADA 2000 A I/O board.
Plug in the new module. Re-install the screw and plug in the cable
ensuring that the cable captive clips are engaged.
3.2.5 Backplane
3.2.5.1 Function
The backplane provides the interconnections for the power, digital, and
other wiring.
3.2.5.2 Operation
The backplane is a passive device which provides various connectors and
interconnections between them via Printed Circuit Board (PCB) tracks. The
backplane does have a 5.1 V DC Transorb and a diode which is designed to
suppress voltage spikes from the +5V DC supply and protect against reverse
polarity.