| New Technology for Incremental Encoders – The DFS Family of Encoders by SICK|STEGMANN |
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While rotary encoders are used in most applications without incident, there are inherent limitations in current encoder designs. The new DFS encoder by SICK|STEGMANN addresses these limitations with all new technology. See the summary below (or download in PDF format) regarding the typical limitations and how they are overcome with the new DFS technology. Or to go directly to the information about the encoders, choose one of the links above:
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Limitations of Conventional Encoders &
the SICK|STEGMANN
DFS Solution
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Conventional Encoder
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DFS Solution
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Limited Pulses Per Revolution
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| Many industrial applications require a higher line count than has been available with traditional incremental encoders. In the past, there were several ways to increase resolution: quadrature, interpolation, or using a larger encoder. |
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| The DFS by SICK|STEGMANN has a completely new ASIC design, which provides 1 to 65,536 pulses before quadrature, and up to 262,144 counts after quadrature; significantly increasing resolution available in incremental encoders, with housings as small as 2 inch in diameter (the 2 inch and 2.5 inch encoders will become available in 2009). |
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Shock, Vibration & Temperature Limitations
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| The rotating discs used in encoders are typically glass or plastic. Glass discs can shatter when exposed to excessive vibration or shock. Plastic discs, while they won’t shatter, cannot achieve the same level of accuracy as glass discs. Additionally, they are limited to a lower working temperature, rendering them unsuitable for the temperature tolerances often required in harsh environments. |
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The DFS encoder features a nickel code disc designed both for increased robustness and a higher temperature tolerance (-20…+100 ºC). |
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Bearing Lifetime and Run Out
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| The life of an encoder bearing can be shortened by several factors: high shaft loads, high speeds of rotation, and shaft misalignment. Once a bearing fails, the encoder needs to be replaced. |
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| The loads on the bearings have been greatly reduced on the DFS due to the 30 mm distance between the bearings. This greater bearing distance also decreases vibration of the encoder, which helps extend the life of the bearings. |
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Programmability
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| Typical encoders are shipped by the manufacturer with the customers’ desired line count, pulse and electrical interface preset and unchangeable. This means that if customers need several encoders with various line counts and/or electrical interfaces, they will need to have several encoders for backup in inventory. |
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| The basic and advanced versions of the DFS allow the user to program the encoder to the line count desired and reprogram it, as needed. |
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Additionally, zero set and electrical interface (to either TTL or HTL) can be programmed,
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 Programming Tool
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| A simple programming tool connected to a PC with a USB cable is used for all programming functions. |
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Axial and Radial Cable Outlets
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| Currently, when users require cable outlets for their encoders, they have the choice of a radial or axial outlet. It is possible they will need encoders with both in the same environment requiring additional inventory. Also, if the cable is somehow damaged, the encoder has to be returned to the manufacturer who will repair the encoder by replacing the cable. |
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| The DFS encoders are available with a pluggable outlet that can be used in either a radial or axial direction which requires less installation depth. Since it is detachable, if the cable is damaged, no repair is necessary by the manufacturer - the customer can simply order a new cable and plug it into the encoder. Various cable lengths and connectors at the end of the cable are also available. |
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Other Features of the DFS
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- ROHS compliant
- High frequency response
- IP 65 Protection Class
- Excellent concentricity
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- High shaft loading
- High operating speed
- Programmable versions come with diagnostic function that reads shaft position
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