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LDV Laser und Lichtsysteme GmbH

An der Wethmarheide 36, 44536 Lünen
Telephone +49 2306 94080-0
Fax +49 2306 94080-33

Hall map

METEC 2019 hall map (Hall 4): stand F29-02

Fairground map

METEC 2019 fairground map: Hall 4

Our range of products

Product categories

  • 11  Measurement and test technology
  • 11.01  Measurement of physical properties and quantities

Measurement of physical properties and quantities

  • 11  Measurement and test technology
  • 11.02  Quality control

Quality control

Our products

Product category: Measurement of physical properties and quantities

Doppler principle

Laser Doppler velocimetry is the method which is most frequently used to measure the speed of solid surfaces without contact. A laser beam is split into two beams of equal intensity using a beam splitter. These two laser beams are processed using optical components, and at a measurement distance, they are placed at the intersection via an adjustable mirror. When two laser beams intersect at an angle, a striped pattern of light and dark strips arises in the measurement volume. The photo receiver sees this pattern of strips and recognises the Doppler frequency in the light which is scattered back, i.e. the frequency caused by the movement of material.

The way a LDV system works is easy to understand if we first consider a single particle, which runs through the striped pattern. In this case, it always transmits a bright pulse of a light when it passes through a light coloured field. The photo receiver records this flash frequency and converts into an electrical frequency in the evaluation unit. This original Doppler frequency is made available to our pulse output from the evaluation unit. Although solid surfaces do not have individual particles, the surface structure behaves exactly the same.

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Product category: Measurement of physical properties and quantities

Velemeter® Series 500

Additionally to the well established Velemeter 500 series a new compact sensor is available. This model is called Velemeter C - it is designed for use in or attached to C-frames of thickness gauges. It has already an integrated angle optic.

Nowadays, it is possible to control the mill gauge in a way that variations in the thickness of the material at the entry side are eliminated in the mill by using the material speed and the measured thickness for mass flow control. However, the new drive technology and the possibilities of gauge control are also responsible for the need of new techniques for speed measurement. The old existing mechanical detectors are no longer state-of-the-art.

The main applications for mass flow control are in the aluminium and stainless steel industry. For the speed measuring device itself, it makes no difference. In all applications VELEMETER® 500 is used.

The gauge head is typically integrated in the extractor hood at the entry and exit side where also the thickness gauges are installed. In some applications, the gauge head is equipped with an angle optic, so that it is possible to mount the gauge head at the same c-frame as the thickness gauge.

Since nearly all new rolling mills nowadays have built-in lasers, the users of old mills know that it is absolutely essential to re-equip their old mills with new measuring and control technology.

For cooling purposes the gauge head is equipped with a liquid-cooled housing which can be supplied from existing cooling facilities or with an own temperature control device or chiller. The VELEMETER® 500 is also able to use the emulsion which is used at the mill for cooling. It is also essential that the laser is able to see the material under all rolling conditions. Therefore, an air purging device which is directly mounted at the laser gauge is used.

As the mass flow control itself is typically supplied by the contractors for the electri-cal part of the mill, it is necessary to con-nect the VELEMETER Model 500 to a host computer. For this reason, the system has a standard pulse output with a resolution of 10 µm.

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Product category: Measurement of physical properties and quantities

Velemeter C

The Velemeter® C provides highly accurate speed and length measurements and all the advantages of non-contact laser based measuring equipment. The sensors are used in mass flow application as well as for elongation measurement.
As a supplementary sensor to the well established Velemeter® 500 series, the Velemeter® C is the more compact version but also makes use of the advantage of a He/Ne Laser tube.

The Velemeter® C is designed for use in or attached to C-frames of thickness gauges and has an integrated angle optic. The sensor head is mounted to the direction of movement of the material, usually at a standard stand-off distance of 450 mm. We can also provide every stand-off distance between 300 and 1500 mm to allow easy mounting at the mill construction.

The digital signal converter box (DAB) has to be mounted in a cubicle by the user. As basic information we supply a pulse output. The pulse frequency is equal the Doppler frequency and can be supplied with 2 or 4 channels according to the RS422 standard. This output is compatible to mechanical encoders.
Based on this, it is possible to do an upgrade from mechanical encoders to non-contact sensors and still use the same mill control system.

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About us

Company portrait

LDV Laser- und Lichtsysteme GmbH took over the business from LDV-Systeme GmbH effectiv Mai 2012. LDV-Systeme was founded in 1999 and is a specialist in the manufacturing of non-contact measurement systems for length and speed measurement.
The main applications for the company’s products can be found in the steel and aluminium industries. Existing systems are produced and further developed in the company’s own development and manufacturing division. Through a global distribution network, years of experience and qualified staff, LDV has achieved a leading position in the global market.

With the acquisition of VH Lichttechnische Spezialgeräte GmbH’s products and associated patents, LDV strategically expanded its product portfolio again in August 2008.

Through the effective use of the light as a working medium, the patented lighting systems enable a faster and clearer identification of surface defects. As a separate division in LDV Laser- und Lichtsysteme GmbH, the products for visual surface examination are incorporated under the name iLux-Lichtsysteme (iLux light systems).