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Laser Velocimeter
Velas DL4000-N

  • High Accuracy
  • Measurement on target up to 1200 °C / 2190 °F
  • Non-Contact, no slippage
  • Designed for steel industry conditions

Features and benefits

The Velas DL4000-N directly replaces traditional, high-maintenance, problematic contact wheel and rollers type devices, with accurate “state-of-the-art” laser Doppler technology. Extremely easy to install, integrate and use.

Accurate speed and length measurement reduces scrap, increases uptime and improves material yield.

  • High accuracy: better than 0.05%.
  • Repeatability: better than 0.02%.
  • Non-Contact: no slippage.
  • Can measure on very high temperature products.
  • No Moving Parts: no wear.
  • Autonomous sensor: ready to use, no calibration required.
  • Designed for easy installation including support with 3 axis plus height adjustment.
  • Water cooling and air purging for the steel industry.
  • Easy Integration: built in Ethernet port.
  • Sensor configuration with PC software through RS485 or Ethernet.
  • Communication protocols: Modbus TCP over Ethernet TCP/IP, Profinet, Profibus-DP, Modbus RTU.

Typical applications

  • Speed measurement for product tracking at crop shear
  • Length measurement: Plate, Tube, Bar…
  • Cut to length applications
  • Control of already cut length
  • Speed synchronisation
  • Differential speed control



The Velas DL4000-N is an autonomous sensor mounted in cast aluminium housing. A hood for protecting the window glass is fitted with air purging to create an air curtain in front of this glass. The case includes a cooling stainless steel pipe and is fixed to a mounting stand, adjustable with three axes. The electrical connections are made with heavy duty connectors.

The Velas DL4000-N has 3 possible standoff distances: 600 mm (red laser), 1200 and 2000 mm (infrared laser).

It is proposed in two models: standard and bi-directional.

The bi-directional velocimeters are used in applications where the target can move in forward and reverse direction, also for low speed application, or if the product can stop, such as position control for cut to length.

Operating principle


The principle is to measure the speed of a moving object using the Doppler effect.

Two laser beams, slightly separated in angle and shifted in frequency, are used to create an interference pattern which will be scattered by the surface of the moving object.

The optical detector (along the optical axis) records a modulated signal including the Doppler frequency. The speed is then calculated analyzing the Doppler shift of the signal.

Finally, the length measurement is computed using a very accurate integration of the speed.


Heat shield kit, to protect from direct radiation

Junction box, including terminal block for connection of power supply and I/Os, and all mandatory laser safety functions for laser class 3B: ON/OFF key switch, emission indicator, remote interlock connector.
Configuration port RS485 (a USB to RS485 adapter is provided).

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