Renishaw: REXT ultra-high accuracy rings

With zero coupling losses and exceptional repeatability, the REXT ultra-high accuracy angle encoder achieves better than ±1 arc second total installed accuracy. Like the RESM encoder, the REXT is a stainless steel ring with the scale graduations marked axially onto the periphery, but with a number of differences to improve upon RESM’s already impressive accuracy.REXT has a thicker cross-section, to ensure that the only signifi cant installation error is eccentricity. Eccentricity is easily removed using 2 readheads, either with Renishaw’s DSi (Dual Signal interface), or by combining the signals inside the host controller. The only errors remaining are graduation errors and readhead SDE, both of which are so small they are often negligible. As a non-contact encoder,REXT offers dynamic performance advantages eliminating coupling losses, oscillation, shaft torsion and other hysteresis errors that plague enclosed encoders. Combining two readheads is easy with the DSi, which also offers an angularly repeatable reference position (propoZ ™) which is unaffected by bearing wander or power cycling. The REXT system operates at temperatures up to +85 °C ( ) and speeds to 4500 rev/min.

Designed for axes that are limited to partial rotation, REXT rings have two reference marks, oriented diametrically opposed, for use with partial arc versions of DSi. DSi processes these reference marks to give a single, angularly-repeatable propoZ reference output.

RENISHAW: REXM/REXT ultra-high accuracy angle encoderSupporting Links