Non-contact optical speed meters and encoders for the precise measurement of speed and length in continuous industrial processes.
Optical encoder speed meters measure the speed and length of moving materials with no mechanical contact at all, eliminating the slip and wear typical of measuring wheels. RODER distributes the ASTech range of optical speed meters, available in two complementary families — VLM60 and VLM500 — covering the whole spectrum of speed and accuracy required by industry.
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What is an optical encoder speed meter
An optical encoder speed meter is an instrument that determines the speed and, by integration, the length of a moving object by analyzing its surface optically. A white-light LED source illuminates the material; the reflected light, modulated by the surface structure, is picked up by an optoelectronic sensor. Since there is no physical contact, the measurement is not subject to slip, wear or maintenance of mechanical parts.
Compared with wheel encoders, optical measurement stays accurate even on delicate, hot, wet or high-speed materials, and leaves no marks on the surface. The absence of harmful LASER light makes these instruments suitable for in-line use without special optical safety requirements.
Two measuring technologies: spatial filter and correlation
ASTech optical speed meters use two measuring principles, chosen according to the speed range and the accuracy required:
- Spatial filter — the light reflected from the surface is modulated by a grating structure implemented on a CCD sensor. The frequency of the resulting signal is proportional to the speed. This is the principle of the VLM500, suitable for high speeds (up to 50 m/s) and very high accuracy (uncertainty < 0.025 %).
- Correlation — successive images of the surface are compared to determine the displacement of the material in the x and y directions. This is the principle of the VLM60, which measures bidirectionally and with no minimum speed, down to 0 m/s.
Advantages over measuring wheels
- No slip: optical measurement does not depend on mechanical grip, the main source of error in measuring wheels.
- No wear or maintenance: no rotating parts in contact with the material.
- No marks on the surface: ideal for delicate, painted or hot materials.
- Almost independent of the material: measures on metal, paper, wood, ceramics, textiles, plastic and rubber.
- Easy integration: pulse encoder outputs compatible with existing systems and standard industrial interfaces.
The two families: VLM60 and VLM500
| Feature | VLM60 | VLM500 |
|---|---|---|
| Measuring principle | Correlation | Spatial filter (CCD) |
| Measuring range | 0 … 300 m/min (0 … 5 m/s) | up to 50 m/s (3000 m/min) |
| Minimum speed | 0 m/s | depending on the version |
| Measurement uncertainty | < 1 % | < 0.025 % |
| Working distance | 100 mm | 185 / 240 / 330 mm |
| Fieldbus | Ethernet (optional) | Profibus DP, Profinet IO, EtherNet/IP |
| Typical use | Replacement for measuring wheels, low speeds | High speed and high accuracy |
VLM60 series
Compact correlation-based optical encoder, bidirectional measurement down to 0 m/s, a direct replacement for measuring wheels. Range 0…5 m/s, working distance 100 mm.
VLM500 series
Spatial-filter speed meter for high speeds (up to 50 m/s) and very high accuracy (< 0.025 %). Four versions and a wide choice of industrial interfaces.
Applications and industries
Optical speed meters are used wherever the speed and length of continuously moving materials have to be measured precisely, without contact:
- Steel and metals: strip, sheet, wire rod, bars, tubes and drawn products, including red-hot material
- Paper and converting: speed measurement on stock, wire and sheet, winders and slitting lines
- Extrusion and plastics: speed control and cut-to-length
- Cables, wires and ropes: length measurement and process control
- Coating and inspection lines: positioning, adjustment and quality control
Frequently asked questions
The optical speed meter measures speed and length without contact, by analyzing the surface of the material optically. Unlike a measuring wheel it is not subject to slip, wear or maintenance, it leaves no marks on the surface and it keeps its accuracy even on delicate, hot or high-speed materials.
The VLM60 is the choice for low speeds (up to 5 m/s), measurement down to 0 m/s and direct replacement of measuring wheels, in a compact format. The VLM500 is suited to high speeds (up to 50 m/s) and very high accuracy (< 0.025 %), with a wide choice of industrial interfaces.
They work on almost any surface: metal, paper, wood, ceramics, textiles, plastic and rubber. Automatic adjustment of the illumination allows them to adapt quickly to different surface conditions.
No. Both the VLM60 and the VLM500 use white-light LED illumination, with no harmful LASER light, which simplifies in-line use from a safety point of view.
Contacts & Information
Contact for general information : info@roder.it
Machine Vision Division of RODER : www.rodervision.com
RODER Instruments Division : www.innovacheck.com
More about RODER : about us
The information contained in this website is provided for information purposes only. Although it has been prepared with the greatest care, it does not constitute a contractual offer or a binding commitment to supply. It may contain transcription, translation or typographical errors. For precise and up-to-date information, please contact our company directly.
Note: Some images on this website have been intentionally generated using artificial intelligence (AI). This is because, for many applications and projects, photographs of the actual installation or system cannot be disclosed owing to confidentiality agreements, contractual clauses and non-disclosure agreements (NDAs).
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