TONiC™ incremental encoder system with RELM20 linear scale
- Readhead size: 35 x 13.5 x 10 mm
- Resolutions to 1 nm
- Speed up to 10 m/s
- Analogue or digital outputs
- Ultra-low Sub-Divisional Error (SDE): typically <±30 nm
- Vacuum compatible version available
- Optical IN-TRAC™ reference mark
- Very high accuracy combined with near zero thermal expansion
- Super-compact encoder with dynamic signal conditioning for improved motion control
- High dirt immunity
- Diagnostic kit to assist challenging installations and aid system optimisation
What is TONiC?
TONiC is Renishaw's super-compact, non-contact encoder system that offers speeds up to 10 m/s and, when combined with the Ti interface, resolutions down to 1 nm for both linear and rotary applications. TONiC systems are quick and simple to install with wide set-up tolerances and calibration at the push of a button. TONiC's dynamic signal processing gives improved signal stability with ultra-low Sub-Divisional Error of typically <±30 nm to help realise superior motion control performance.
What is RELM20 scale?
RELM20 is a spar scale manufactured from ZeroMet™, a low expansion nickel/iron alloy, featuring a 20 µm pitch.
It is comparable to fine pitch glass scales and offers a total accuracy (including slope and linearity) better than ±1 µm over a 1.5 m length. ZeroMet has a coefficient of thermal expansion of 0.75 ±0.35 μm/m/°C at 20 °C.
System designers can choose between specially formulated 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?
Ease of handling
The RELM20 ZeroMet low thermal expansion scale has a much smaller cross section than typical glass scales and allows easier handling and installation without risk of breakage, making it ideal for the most demanding precision applications.
Ultimate reliability and performance in a compact size
For ultimate reliability, consistent performance and high dirt immunity, TONiC readheads incorporate third-generation filtering optics, tuned for even lower noise (jitter) and now further enhanced by dynamic signal processing including Auto Gain Control and Auto Offset Control. This combination – all incorporated inside the readhead - provides signals of unrivalled purity and ultra-low Sub-Divisional Error of typically <±30 nm. The result is smoother velocity control for improved scanning performance and increased positional stability; essential parameters for so many applications, all in a compact readhead.
Quicker and easier installation
A set-up LED on the readhead gives a visual indication of signal size and an optional diagnostic kit allows remote checking of the system performance when the readhead is concealed within the machine. Calibration of the reference mark and incremental signals is done at the push of a button with no mechanical adjustment or additional diagnostic tools. The IN-TRAC customer-selectable optical reference mark is embedded in the incremental scale for compact dimensions and simplified alignment. This yields a reference mark output that is bi-directionally repeatable to unit of resolution over the full operating temperature and speed range.
TD (dual resolution) interface
- Selectable dual-resolutions quadrature output.
- Ideal for applications that require high speed movement combined with finer precision motion.
DOP (dual output) interface
- Provides simultaneous digital quadrature and 1 Vpp signals.
- Designed for applications requiring one or more operations to be synchronised with a motion axis.
Optional diagnostic kit
TONiC diagnostic software can be used to optimise the installation of TONiC encoders and provide a quick and comprehensive system calibration. The software must be used in conjunction with the TONiC diagnostic hardware which can be purchased from Renishaw using part number A-9411-0011. The hardware is connected to the PC via the USB cable (provided in the kit) or in-line with the customers' electronics.
Find out all about the TONiC diagnostic kit.
RELM20: high accuracy ZeroMet spar scale with mid reference mark
Also available with end reference mark as RELE20
Readhead size (LxWxH)
35 mm x 13.5 mm x 10 mm
Coefficient of thermal expansion at 20 °C
0.75 ±0.35 μm/m/°C
Accuracy grade at 20 °C
Certified to ±1 μm, calibration traceable to International Standards
IN-TRAC reference mark
Various reference mark position options, see data sheet for details
Dual or single limits (select at time of order)
20 mm to 1.5 m
(See data sheet for details)
Up to 10 m/s at -3 dB
Up to 10 m/s
Sub-Divisional Error (SDE)
Typically <±30 nm
Dynamic signal control
Real time signal conditioning including Auto Gain Control (AGC) and Auto Offset Control (AOC) for optimised performance during operation
1 Vpp (20 μm period)
Resolutions from 5 μm to 1 nm
0.5 m, 1 m, 1.5 m, 3 m, 5 m and 10 m cable lengths with mini connector (connects direct to TONiC interface)
5 V ±10%, <100 mA (analogue system), <200 mA (digital systems) (unterminated)
100 m/s2 max @ 55 Hz to 2 000 Hz
1 000 m/s2, 6 ms, ½ sine
Operating temperature (system)
0 °C to +70 °C
Refer to data sheets for full details.
How it works
TONiC features the third generation of Renishaw's unique filtering optics that average the contributions from many scale periods and effectively filter out non-periodic features such as dirt. The nominally square-wave scale pattern is also filtered to leave a pure sinusoidal fringe field at the detector. Here, a multiple finger structure is employed, fine enough to produce photocurrents in the form of four symmetrically phased signals. These are combined to remove DC components and produce sine and cosine signal outputs with high spectral purity and low offset while maintaining bandwidth to beyond 500 kHz.
Fully integrated advanced dynamic signal conditioning, Auto Gain , Auto Balance and Auto Offset Controls combine to ensure ultra-low Sub- Divisional Error (SDE) of typically <±30 nm.
This evolution of filtering optics, combined with carefully-selected electronics, provide incremental signals with wide bandwidth achieving a maximum speed of 10 m/s with the lowest positional jitter (noise) of any encoder in its class. Interpolation is by CORDIC algorithm within the TONiC Ti interface, with fine resolution versions being further augmented by additional noise-reducing electronics to achieve jitter of just 0.5 nm RMS.
The IN-TRAC reference mark is fully-integrated in the incremental scale and is detected by a split photodetector within the readhead. As the diagram shows, the reference mark split detector is embedded directly into the centre of the incremental channel linear photodiode array ensuring greater immunity from yaw-dephasing. Yielding a reference mark output that is bi-directionally repeatable to unit of resolution at all speeds. This unique arrangement also benefits from an automatic calibration routine that electronically phases the reference mark and optimises the dynamic signal conditioning