Dual readhead encoding made easy with DSi Dual SiGNUM Interface


Renishaw's new DSi rotary encoder makes it easy to bring high accuracy positioning to medical, scientific, and industrial rotating devices. Capable of total installed accuracy of better than 1 arc second, the DSI combines two error-correcting SiGNUM SR readheads on an RESM ring and provides a customer-selectable propoZ reference (index) position completely unaffected by bearing wander or power cycling. Located in 180° opposition, the two readheads eliminate odd error harmonics, including eccentricity, and compensate 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.

DSi maintains the dynamic advantages of SiGNUM encoders. As a non-contact system, SiGNUM 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 encoder range, DSi is capable of operating at speeds up to 4,500 rev/min and temperatures up to 85°C.

The result is total installed error of typically ±2.5 arc second (with 200 mm diameter RESM ring). For ultimate precision, DSi can be combined with a 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 reference (index) output, which is completely unaffected by bearing wander or power cycling. The customer selects the desired propoZ 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 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.
SiGNUM encoder design features rugged IP64 sealed readheads, dynamic signal processing for excellent reliability, and ultra-low cyclic error (<±40 nm). In addition, comprehensive SiGNUM software enables optimum set-up and real-time diagnostics via a PC's USB port.
As with all Renishaw products, the SiGNUM range is backed up by a worldwide team offering truly responsive global support.
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