When placing the electrical multimeter on the rail ensure the meter is placed in the same direction as the rail and NOT placed across the rail. This will mean that the top of the meter is always facing a block joint.
Place the digital multimeter on top of the rail ensuring the top of the meter is 15mm from the ''T' Piece.
Use the following table to decide if your block joint is functioning correctly.
0 - 2 Bars IBJ: Good
3 - 5 Bars IBJ: Partial Short
6+ Bars IBJ: Defective
Be aware of section rail jumpers running past the block joints and giving false readings. If a jumper cable runs past the block joint and a high reading is observed, try moving the cable away from the block joint and see if the reading decreases.
If the jumper cable cannot be moved and the reading is:
1. 1-3 bars: ignore the reading and consider the lBJ as good.
2. Above 3 bars: Consider the IBJ as defective or partially shorting.
If you find this condition. arrange for the cable to be re-run away from the block joint.
Looking for earths or short circuits
1. Take a measurement both at the start and end of the failing track circuit 200mm from the track connections, this
measurement should be made towards the middle of the failing track circuit and not towards the block joint.
2. If the readings vary from the "T" end of the track to the ''TR" end of the track
by more than 2 bars, then it indicates an earth or short circuit.
3. Keep monitoring the bars on the current analyser along the track until you find the position that the reading changes.
This identifies the position of the earth or short circuit.
4. Probable causes are: a) trainstops shorting to the section rail. b) trainstop earth bonds touching the section rail, c) point insulation shorting,
or d) the section rail shorting to the tunnel segment via metal objects, rail keys or defective rail chairs.
5. lf you find that the meter gradually decreases as you move along the track and there is not one specific point where the meter reading
changes, likely causes could be wet beds or flooding of the track.
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