Diagram of the non-contact overhead line measurement

Distance measurement by phase shift measurement

Measuring system for non-contact catenary wire measurement at high measuring speeds. It consists of the climatised sensor head, the high performance data processing unit and the control unit.

For the distance measurement, a semi-conductor laser in the sensor head is modulated with high frequency at a sine-wave form and guided vertically upward by means of an oscillating mirror. When the laser beam hits the contact wires to be measured and/or other objects, it is reflected and the phase shift is measured by a detector. The distance can then be calculated from the phase shift of the emitted and reflected laser light.

To measure the horizontal position, the laser beam is deflected laterally by ±35° by means of a mirror oscillating at 50 Hz. The specific distance is then measured in relation to the associated angle. The vertical and horizontal position can be calculated from the determined distance and angle.

The Plasser Clearance/Ballast Measuring System utilises a Laser Mirror Scanner, type LMS-Q250. The Laser Mirror Scanner is a high speed profile measuring device based upon accurate distance measurement using an electro-optical range detection method and a beam scanning mechanism.

The Laser Mirror Scanner scans a 360° range, delivering profile data at almost 360° (5°-355°) per scan.

The Laser Mirror Scanner is connected to the Plasser Server via an Ethernet Network connection.

The Plasser Server receives one data packet (1001 points, containing measured distance and quality indication of measurement) from the Laser Mirror Scanner for every foot (or 25 cm) traveled. The index of the points indicates the current angle of the laser beam.

• High-speed profile measuring system
• Used for clearance measurement as well as ballast cross section measurement
• Scan range 360°
• Up to 40 scans/sec
• Sealed weatherproof housing (IP64)
• Reliable time of flight measurement principle
• Easy and flexible Ethernet interface
• External distance synchronisation input
• 1001 measurement points per revolution
• Laser class 2 in scanning mode (eye save)
• Additional point mode (non-scanning) with co-aligned visible beam pointer
• Laser class 1 in point mode (eye save)

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