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Encoder is `first` to offer 27-bit resolution at 36,000 rpm

18 April, 2009

Renishaw has announced what it claims is the world’s first absolute encoder capable of 27-bit resolution at 36,000 rpm. The Resolute encoder offers a 1nm resolution at speeds of up to 100 m/s for both linear and angular applications.

The encoder avoids the conventional arrangement of side-by-side incremental and absolute tracks, which Renishaw says can result in de-phasing problems when angular misalignment is introduced. Instead, it uses a single-track scale that combines the absolute position and embedded phase information in one code. This design is said to provide much wider set-up tolerances.

The enhanced detection method is said to provide a sub-divisional error of ±40 nm, resulting in better surface finish for machined parts, better scanning and velocity control, and solid servo stiffness on linear motors or rotary direct-drives when holding position.

The new system acquires absolute position immediately on switch-on, without needing a battery back-up or reference returns. Its optics can read a 30µm scale with a jitter of less than 10nm rms.

The linear encoder version is available with “zero expansion” invar spars that offer ±1µm accuracy over lengths of up to 1m, or with robust stainless steel spars offering an accuracy of ±4µm over 5m. For quick installation, there is also a tape scale with a ±5 µm/m accuracy.

For angle encoder applications, there is a range of rings with diameters from 52–550mm, with larger sizes to order.

The IP64-protected read head is unaffected by dirt on the scale, and incorporates a sensor that signals an alarm if the temperature rises above 80°C. Signal monitoring, position-checking and speed monitoring are carried out constantly inside the head.

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