Renishaw’s new REXM high accuracy angle encoder offers the ultimate angular metrology…

June 2007

For applications that require the highest angular accuracy, the REXM angle encoder offers new levels of angular metrology - better than ±1 arc second total installed accuracy, zero coupling losses and exceptional repeatability.

Like the RESM, the REXM stainless steel ring has graduations marked directly onto the periphery. However, it features a thicker cross-section designed to minimise all installation errors except eccentricity.

The remaining eccentricity is easily corrected using the combined output of two readheads. Renishaw's new DSi (Dual SiGNUM™ Interface) blends the output of two readheads whilst providing a repeatable and customer programmable reference mark propoZ™ position. Once the DSi has eliminated eccentricity, the only other errors remaining are graduation and cyclic error (sub-divisional error - SDE) both of which are exceedingly small.

When REXM is used with the DSi, it is possible to achieve a total installed accuracy of better than ±1 arc second. Tests on a 183mm REXM ring have achieved an impressive total installed accuracy of ±0.22 arc seconds.

Furthermore, REXM maintains the dynamic performance advantages of SIGNUM™ encoders. As a non-contact system, REXM rings are directly locked to the rotor, eliminating coupling losses, oscillation, shaft torsion and other hysteresis errors that plague enclosed encoders.

The total installed accuracy of a typical REXM system is ±0.22 arc second, determined by analysis of sequentially rotated installations.