NR/SMS/APPENDIX ISSUE 6
Signal Maintenance Specifications (SMS): Appendices
| Organization: | NR |
| Publication Date: | 3 March 2018 |
| Status: | inactive |
| Page Count: | 395 |
scope:
General
These systems have one type (DEK43) of rail mounted wheel detectors (heads). Wheel detection is provided by two different types of systems: ZP 43V Analogue (the original type) and ZPD 43 Digital.
The differences are limited to the components and method of operation of the equipment within the trackside connection box.
The voltages and frequencies transmitted between an axle counter evaluator and the ZP 43V and the ZPD 43 wheel detection systems are essentially the same
Currently two different AzS axle counter evaluator systems are in use on Network Rail infrastructure; these are the AzSM (E) and the AzS 350U.
The Wheel Detection Equipment consists of a rail mounted double wheel sensor and equipment within the trackside connection box that provides an output to the axle counter evaluator.
The DEK 43 consists of two detectors mounted in one unit on one rail that detects the passing wheels of the vehicles. As they pass, the wheels influence the electromagnetic field between the transmitter and the receiver of each detector; this alters the voltage induced in the receiving coil of the detector.
This voltage is converted by the trackside connection box to frequency/amplitude-
The Evaluation Computer used can be either a AzSM (E) or a AzS 350U system. The ZAN card (in the AzSM (E)) or the VESBA card (in the AzS 350U) converts the signals from wheel detection equipment into a series of logic pulses so that the microprocessor in the evaluation computer can determine the train's direction of travel & the number of axles.
The Evaluation Computer interprets the signals transmitted by the counting heads. It then compares the numbers of axles, which have entered and left a track vacancy detection section to determine whether that track vacancy detection section is clear or occupied.
In the case of the AzS 350U evaluator the clear/occupied state of each track vacancy detection section determines whether the corresponding TR (track relay) is energised or de-energised, while the AzSM (E)) transmits the states of the track sections directly to the interlocking via the IL bus.
Up to 16 counting heads (ZP 43 V units) can be connected per evaluation computer in the AzSM (E) system. The AzS350U can have up to 5 counting heads (ZP 43 V units) connected per evaluation computer
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