Specifications

RailCorp Engineering Manual — Signals — Equipment Manual

Cerberus Level Crossing Monitor Field Equipment Manual TMG E1261

Issued August 2012 UNCONTROLLED WHEN PRINTED Version 2.1

2.2.5.5 Replacement Procedure

Remove the I/O board, ADC board and the DC/DC converter power supply to allow

access to the backplane PCB. Removal is done by removing all of the mounting screws

disconnecting the 10-way ribbon cable, disconnecting the 4 power supply wires and lifting

the board out.

On replacement of the backplane PCB ensure that the power supply wires are connected

to their proper terminals. Incorrect wire placement will cause extensive damage to most

components. See Specification 1072 if you are unsure of the proper connections for the

power supply to backplane connections.

2.3 Current sensor

2.3.1 Description

The current sensor is a Klippon rail mounted device. The module has an identification

label of "LXMON/2.0 CSN". Refer to drawing M08-854 for details of its physical aspects.

Refer to drawing M08-855 in Appendix D for circuit drawing.

2.3.2 Function

The current sensor uses a Hall Effect device to monitor the current in the wire that is

threaded through its aperture. It does not affect the circuit in which the current is being

measured. The Hall Effect device measures the magnetic field created by current flowing

in the wire. Tong and clamp meters also use Hall Effect devices for measuring DC

currents.

2.3.3 Operation

Power is connected to the current on terminals 1 and 2. Terminal 1 is 0 volts and terminal

2 is +12 VDC.

The output is a voltage between terminals 1 and 4. Terminal 4 being positive in respect to

terminal 1. The output voltage is linear in respect to the current in the circuit being

measured.

Output Voltage = Current (A) / 4.

Level Crossing lamps draw approximately 2.5 amps each (10V 25 watt globes).

Therefore the output voltage of the current sensor for a 2 lamp a side level crossing

(crossing without gates) while lamps are flashing is about 5 amps / 4 which is 1.25 volts.

The current sensor can measure currents in the range of 0.28 amps to 20 amps. Note

that because of characteristics of the Hall Effect device the current sensor typically has

an output voltage of about 70 millivolts when their is no current following in the circuit

being measured.

2.3.4 Configuration and Set-up

Normally the link on the current sensor PCB is in the DC position (LK1 on some units). It

may be necessary to move the link to the AC position (LK2 on some units) if there are 12

Volt DC Signal lamps fed from the location. When the Signal changes aspect there may

be considerable induction into other circuits which the current sensor is sensitive enough

to pick up. The monitor will then alarm because it detected lamp current when the

crossing lamps should have no current. The current sensors are susceptible to electrical