RESOLUTE™ UHV absolute encoder system with RELA linear scale
- Protocols available: BiSS®, Panasonic
- Readhead size: 36 x 16.5 x 17.2 mm
- Resolutions to 1 nm at 100 m/s
- ±1 µm accuracy at 20 °C
- Scale thermal coefficient of expansion at 20 °C: 0.75 ±0.35 µm/m/°C
- Very high accuracy combined with near zero thermal expansion
- Excellent motion control performance
- Wide set-up tolerances
- Low outgasing for vacuum environments
- Less than 10 nm RMS jitter for improved positional stability
- ±40 nm Sub-Divisional Error for smooth velocity control
What is RESOLUTE UHV?
RESOLUTE UHV brings absolute encoder technology to Ultra-High Vacuum applications, allowing customers to achieve higher throughput, reduce risks of damage and increase dependability.
RESOLUTE outperforms all other absolute encoders that are designed for UHV environments. Capable of 1 nm resolution and up to 100 m/s, RESOLUTE provides a specification that breaks new ground in encoder technology.
Winner of a Queen's Award for Enterprise 2015 in the Innovation category
What is RELA scale?
RELA is a spar scale manufactured from ZeroMet, a low expansion nickel/iron alloy, featuring our 30 µm pitch absolute scale code.
It is comparable to fine pitch glass scales and offers a total accuracy (including slope and linearity) better than ±1 µm up to 1 m length. ZeroMet has a thermal expansion coefficient of 0.75 ±0.35 µm/m/°C at 20 °C.
System designers can choose between specially formulated UHV compatible adhesive tape or mechanical clips to suit mounting requirements. Both mounting methods allow for independent thermal expansion to that of the substrate.
Why choose this encoder system?
UHV (Ultra-High Vacuum)
RESOLUTE UHV takes Renishaw's revolutionary absolute encoder technology and delivers it in a readhead that is suitable for use in Ultra-High Vacuum conditions up to 10 -9 Torr. The new range of RESOLUTE UHV encoders are constructed from clean residual gas analysis materials (RGA) making them suitable for high performance, semiconductor and scientific applications.
Excellent motion control performance
RESOLUTE UHV's industry-leading performance is the result of a sophisticated, reliable and innovative method of operation. Crucially, the system uses a single track non-repeating “bar code” scale format with a nominal pitch of 30 µm. With its sophisticated optical design the RESOLUTE readhead captures a near-instantaneous image of this scale which, when analysed, allows a unique position to be identified at speeds of up to 100 m/s. The system allows position to be determined with resolution as small as 1 nanometre (1 billionth of a metre) and with low noise (jitter below 10 nm RMS) and SDE (Sub-Divisional Error, the error within a scale period) of just ±40 nm. This provides encoder feedback of superior fidelity, to ensure smoother velocity control and rock-solid positional stability.
Wide set-up tolerances
RESOLUTE UHV does not follow the conventional technique of using dual tracks side-by-side (one incremental, one absolute) which inherently suffers de-phasing problems when small amounts of angular misalignment are introduced. Instead, this absolute encoder features a single track, optical absolute scale, combining both the absolute position and embedded phase information into one single code. This technology provides RESOLUTE UHV with far wider set-up tolerances (yaw tolerance ±0.5°) for quick and easy installation and superior long-term reliability, even if the motion axes settle or move over time. To further aid installation and diagnostics, there is an integral set-up LED on the readhead.
|Protocol||Description||Data sheet||Compatible products|
Renishaw supports BiSS C (unidirectional) open protocol for absolute encoders. BiSS is a high-speed serial protocol, perfect for dynamic axes that require high acceleration, smooth velocity control, excellent bi-directional repeatability and rock-solid positional stability.
RESOLUTE with Panasonic serial communications interface is available in linear and rotary forms. Compatible with the A5 and A6 series of drivers, it provides high resolution repeatable feedback for better servo and speed control.
RELA: absolute coded high accuracy ZeroMet spar scale
Readhead size (LxWxH)
36 mm x 16.5 mm x 17.2 mm
Nominal 30 μm
Thermal expansion coefficient at 20 °C
0.75 ±0.35 μm/m/°C
Accuracy grade at 20 °C
Certified to ±1 μm, calibration traceable to International Standards
Some BiSS C protocol variants have limited maximum length
(See data sheet for details)
80 mm to 1.5 m
(See data sheet for details)
Up to 100 m/s
BiSS C Panasonic
BiSS C: 50 nm, 5 nm and 1 nm resolutions
Panasonic: 100 nm, 50 nm and 1 nm resolutions
Sub-Divisional Error (SDE)
Up to 10 m cable lengths with flying lead
5 V ±10%, max 250 mA @ 5 V (terminated)
100 m/s2 max @ 55 Hz to 2 000
1 000 m/s2, 6 ms, ½ sine
0 °C to +75 °C
Bake-out temperature (non-operating)
Silver-coated copper braided single screen. FEP core insulation, over tin-plated copper wire.
Refer to data sheets for full details.
*Other protocols are continually being added.
How it works
RESOLUTE communicates bi-directionally in purely serial format, using a variety of industry-standard protocols, of both proprietary and open standard.
The process begins...
The controller initiates operation by sending a demand message to the readhead, instructing it to capture the absolute position on the linear or rotary scale at that instant. The head responds by flashing a high-power LED source to illuminate the scale. The flash duration is as brief as 100 ns to minimise image blur on moving axes. Crucially its timing is controlled within a few nanoseconds to preserve the relationship between demanded and reported position, one of the essential features that makes RESOLUTE ideally suited to very high specification motion systems.
Single track scale
The scale is essentially a single track of full-width contrasting lines, based on a nominal period of 30 µm. The absence of multiple parallel tracks gives important immunity from yaw errors and much more lateral tolerance in head position.
The scale is imaged, via an aspheric lens which minimises distortion, onto a custom detector array designed specifically for RESOLUTE. The optical arrangement, with a folded illumination path but direct imaging, is highly compact yet stable thus assuring the fidelity essential for excellent metrology.
Data decoding and analysis
Once captured by the detector, the image is transferred via an analogue-to-digital converter (ADC) to a powerful Digital Signal Processor (DSP). Specially developed algorithms then obtain a true absolute, but relatively coarse position from the code embedded in the scale. This process is checked, and corrections are made by further algorithms in the DSP which exploit redundancy and intentional restrictions in the scale code. Meanwhile other routines calculate a very high resolution fine position, which is then combined with the coarse position to provide a truly absolute and very high resolution location.
Final checks and data output
After final error checking procedures this information is uploaded in the appropriate protocol to the controller as a pure serial word representing position to within 1 nm. Protection against electrical noise disturbance is provided by addition of a Cyclic Redundancy Check (CRC). The entire process can take as little as a few microseconds and be repeated up to 25 000 times per second. By a variety of techniques, including adjusting the light flash duration to the axis speed, this performance is achieved at up to 100 m/s while, crucially, preserving exceptionally low positional jitter at lower operating speeds.
And the result is...
An encoder with generous installation tolerances: RESOLUTE allows ±0.5° in yaw, pitch and roll and an impressive ±150 µm in rideheight. Meanwhile the generous optical footprint and advanced error correcting procedures confer excellent immunity to optical contamination, both particulate and greasy smears. All this while maintaining 1 nm resolution at 100 m/s: RESOLUTE is the answer to the toughest absolute challenge.