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.
REXM20 has a thicker cross-section, to ensure that the only
significant installation error is eccentricity. Eccentricity is easily removed
using two 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, REXM20 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.
REXM20 total installed accuracy grades:
![](/v/vspfiles/assets/images/REXM04.png)
Designed for axes that are limited to partial rotation, REXT20
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.
Features
With zero coupling losses and exceptional repeatability, the
REXM/REXT ultra-high accuracy angle encoder achieves better than ±1 arc second
total installed accuracy.
•
Use with two VIONiC™, TONiC™ or SiGNUM™
encoders, combined with DSi to give ultra-high accuracy
•
Installed accuracy to ±1 arc second with dual readheads
•
Wide range of standard sizes from 52 mm
to 417 mm
•
Large internal diameter for ease of
integration
•
Flange mounted with easy 4-point
adjustment method
•
Angularly repeatable propoZ reference
position is unaffected by bearing wander or power cycling
REXM ultra-high accuracy rings
|
For ring diameters >417 mm please contact EPD
|
Series
|
Scale
pitch
|
Form
|
Diameter
|
Part
number
|
Price US$
|
REXM
|
20U (20 µm)
|
A (standard section)
|
052
|
REXM20USA052
|
2,066
|
057
|
REXM20USA057
|
2,066
|
075
|
REXM20USA075
|
2,239
|
100
|
REXM20USA100
|
3,702
|
103
|
REXM20USA103
|
3,702
|
104
|
REXM20USA104
|
3,702
|
115
|
REXM20USA115
|
3,746
|
150
|
REXM20USA150
|
3,789
|
183
|
REXM20USA183
|
3,875
|
200
|
REXM20USA200
|
3,961
|
206
|
REXM20USA206
|
3,961
|
209
|
REXM20USA209
|
3,961
|
229
|
REXM20USA229
|
4,133
|
255
|
REXM20USA255
|
4,362
|
300
|
REXM20USA300
|
5,769
|
350
|
REXM20USA350
|
6,888
|
417
|
REXM20USA417
|
8,955
|
Supporting Links
RENISHAW: REXM/REXT ultra-high accuracy angle encoder