Rotary Encoder provides high accuracy positioning.

Press Release Summary:

Offering better than ±1 arc second total installed accuracy, Dual SiGNUM interface Rotary Encoder combines two IP64-sealed SiGNUM SR readheads on RESM ring. It provides customer-selectable propoZ(TM) reference output, which is completely unaffected by bearing wander or power cycling. Encoder is capable of operating at speeds up to 4,500 rpm and temperatures to 85°C. SiGNUM(TM) software enables set-up and real-time diagnostics via PC's USB port.

Original Press Release:

Dual Readhead Encoding Made Easy with DSi Dual SiGNUM(TM) Interface

DSI rotary encoder offers better than ±1 arc second total installed accuracy

September 2006 - Renishaw's new DSi (Dual SiGNUM interface) rotary encoder makes it easy to bring high accuracy positioning to rotary tables and other rotating devices. Offering better than ±1 arc second total installed accuracy, the DSI combines two SiGNUM SR readheads on an RESM ring and provides a customer-selectable propoZ(TM) reference (index) position completely unaffected by bearing wander or power cycling.

Precision rotary axes often demand very high accuracy without calibration or error-map compensation. As a modular solution, DSi adds a second readhead at 180° opposition, which eliminates odd error harmonics including eccentricity and compensates for the effect of bearing wander. By combining the incremental signals from the two readheads and using patented reference mark processing, the DSi appears to the controller as a single very high accuracy encoder.

The result is total installed error of typically ±2.5 arc second (200 mm diameter RESM). For ultimate precision, DSi can be combined with the new ultra-high accuracy REXM ring to offer better than ±1 arc second total installed accuracy.

DSi provides the angularly repeatable and customer located propoZ(TM) reference (index) output, which is completely unaffected by bearing wander or power cycling. The customer selects the desired propoZ(TM) reference position by driving the axis to the chosen angle and simply pressing a button. This feature makes alignment of the encoder's reference position to the T-slots on a machine tool rotary table, for example, faster and more precise. The selected angle is then stored in the DSi's memory so the patented propoZ(TM) reference (index) is locked to that angle, ensuring perfect angular repeatability, even if the center of rotation of the axis moves while the DSi is switched off.

An integrated mounting ring and scale make adding a second SR readhead very easy. Furthermore, DSi maintains the dynamic advantages of SiGNUM(TM) encoders. As a non-contact system, SiGNUM(TM) RESM rings are taper-locked to the rotor shaft, ensuring a compact axis design and the elimination of coupling losses, oscillation, shaft torsion and other hysteresis errors that plague enclosed encoders.

Like the rest of the Renishaw SiGNUM(TM) encoder range, DSi is capable of operating at speeds up to 4,500 rev/min and temperatures up to 85°C. SiGNUM(TM) also benefits from rugged IP64 sealed readheads, dynamic signal processing for excellent reliability, and ultra-low cyclic error (<±40 nm). In addition, comprehensive SiGNUM(TM) software enables optimum set-up and real-time diagnostics via a PC's USB port.

As with all Renishaw products, the SiGNUM(TM) range is backed up by a worldwide team offering truly responsive global support.

For more information on Renishaw's encoders, contact Howard Salt, Business Manager, Encoder systems, Renishaw Inc., 5277 Trillium Boulevard, Hoffman Estates, IL 60192. Phone 847-286-9953; fax 847-286-9974. Email:
For a detailed look at other productivity enhancements for metrology, linear and rotary position feedback, and machine tool calibration, visit Renishaw's web site at:

Inquiries should be directed to:
Susan Wilm,
Marketing Assistant
Renishaw Inc.
5277 Trillium Blvd.
Hoffman Estates IL 60192.

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