Specifications

Engineering Standard –NSW
Signalling SMS 02
Cerberus Level Crossing Monitor Equipment
March 2005 Version 1.2 © Australian Rail Track Corporation Page 30 of 118
This document is uncontrolled when printed.
output voltages. They should be (+5, +12, -12 VDC). The pin-
outs for the PSU are either on the top or the sides of the PSU.
(e)To test remove the power supply connector from the rear of the
backplane and test the power supply using a voltmeter between
0V and +5V, +12V and -12V. If the +5V rail is less than 4.7V the
system will not work.
(f) The +5V may be tested in circuit using the test points on the
Input or Output Optoisolator Boards.
3.2.3.5 Replacement Procedure
For the main box, if the PSU has failed, remove and replace the
whole main box. The PSU can be replaced in the workshop.
The power supply is a PD65-31 LC from PowerBox for a V1.0/V2.0
monitor or a NFC25-12T05-12 from Computer Products - Power
Conversion for a V3.0 monitor.
3.2.4 Analogue to Digital Converter
(ADC) 3.2.4.1 Function
The analogue to digital converter provides 8 analogue inputs the
level crossing monitor can monitor and log. They are used to
measure the Battery voltage, Lamp currents and Battery Test
currents. It is mounted on a connector on top of the I/O board.
3.2.4.2 Operation
This board is connected to the rear panel 8-way connector via a
ribbon cable.
Pin 1 of the 8-way connector is internally wired to the incoming +'ve
supply. This connects the Level crossing battery to analogue
channel number 1 on the ADC. Analogue inputs 2-8 are available
on the rear panel for connection to the lamp and battery current
sensors.
Due to the voltage drop of approximately 0.16V DC between the level
crossing battery bus and analogue input number 1 of the ADC
board the measured voltage will be 0.16V DC less than the bus
voltage. To compensate for this the level crossing monitor software
through the expression file automatically adds 0.16V DC to the
displayed voltage so that the bus voltage and the voltage detected
by the monitor are within 0.1 V DC of each other.
The ADC is a 8 bit Analogue to Digital converter. The board has an
onboard voltage reference to provide greater accuracy. The ADC
converts the incoming voltage to a 8-bit digital signal which is then
used by the SCADA I/O microprocessor to detect the battery
voltage and the number of operating lamps.
3.2.4.3 Configuration and Set-up
There is no configuration or set-up required for the ADC.