Specifications

Engineering Standard –NSW
Signalling SMS 02
Cerberus Level Crossing Monitor Equipment
March 2005 Version 1.2 © Australian Rail Track Corporation Page 18 of 118
This document is uncontrolled when printed.
Current Sensor units. The Current Sensor that has a linear output
voltage of 0 to 5 volts in response to a lamp current of 0 to 20 amps.
For a standard level crossing two sets of lamps are connected to each
flasher unit (PTF3B or Safeflash). An electronic flasher (PTF3B or
Safeflash) flashes between the two sets of lamps at about 43 times per
minute. The Current Sensors are connected to the common leg of the
two sets of lamps. The two sets of lamps are identified as Flasher Up
and Flasher Down. While the lamps are flashing the Current Sensor is
measuring the current both sets of lamps. To allow the level crossing
monitor to know which set of lamps relates to the current being
measured a digital input (via a VIO) is used to monitor the state of the
flasher (Flasher Up or Flasher Down or in the case of Safeflash - Bank 1
or Bank 2). This digital input tells the level crossing monitor which set
of lamps is currently lit and the monitor than knows the current reading
for each set of lamps.
A change is considered to have occurred on a lamp analogue channel
when a different number of lamps is determined to be operating.
Analogue inputs 6 to 7 are electrically conditioned for a 0 to 5 volts DC
input voltage. They are normally spare and may be used with other
sensors to monitor additional flashing lamps OR log voltage, current or
temperature. A possible use for the spare inputs is to use a Vital
Analogue Interface module (supplied by Signal Engineering) to directly
monitor DC track relay voltages. Another useful application is the
monitoring of the location hut temperature and even monitoring of the
rail temperature.
Analogue input 8 is electrically conditioned for a 0 to 5 volts DC input
voltage. It is normally used to monitor the Level Crossing battery test
current in the range of 0 to 20 amps DC. To monitor the battery test
current it uses a Current Sensor (same unit as used for the lamps) that
has a linear output voltage of 0 to 5 volts in response to a lamp current
of 0 to 20 amps. A change is considered to have occurred when the
current is more than 1.6 ampere different than the last logged value.
2.8 Battery Testing
The level crossing monitor has a facility for testing the capacity and
terminal voltage of the level crossing battery and reporting the results to
a remote location or Control Centre via a dial-up modem.
The level crossing monitor uses outputs 1 and 8 (that is Battery Test,
and Timer Test) to control the battery test circuitry. These outputs
control the 120 V AC supply to the level crossing battery charger, and a
test load for the level crossing battery.
The process of testing the level crossing battery after a request is
received from a Control Centre or maintainer takes approximately 8
minutes to complete