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RGH24 incremental encoder system with RGS20 linear scale


  • Readhead size: 36 x 13.5 x 14.8 mm
  • Resolutions to 10 nm
  • Speed up to 8 m/s*
  • Analogue or digital outputs
  • Low Sub-Divisional Error (SDE): typically ±0.15 µm


  • Proven reliability
  • Compact readhead
  • Digital RS422 output direct from the readhead
  • Scale lengths available up to 50 m (>50 m special order only)
  • ‘Cut-to-length' scale flexibility
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What is RGH24?

The RGH24 is a compact readhead with integral interpolation which offers industry standard digital and analogue outputs. Its non-contact design offers high speed, reliable operation with zero friction and zero wear.

What is new?

Higher clock frequencies are available for faster linear speeds. The new RGH24 variants are now capable of achieving 3 m/s at 0.1 and 0.2 µm resolution.

What is RGS20 scale?

RGS20 is a tape scale manufactured from a thin flexible steel strip, featuring a 20 µm pitch, which is gold plated to give high reflectivity and corrosion resistance. It may be mounted using adhesive backing tape, to most engineering materials, including metals, ceramics and composites. Secured to the substrate with scale end-clamps, RGS20 is mastered to the substrate and will match the substrate's thermal expansion. The scale is supplied on a reel and can be cut to suit any axis length up to 50 m. 

Why choose this encoder system?


The RGH24 readhead with RGS20 scale is a robust and reliable encoder system with a proven pedigree to ensure low cost of ownership.


The compact size of the RGH24 readhead allows for easy integration into many applications with limited space.

Direct output

The RGH24 outputs RS422 digital resolutions from 5 µm to 10 nm direct from the readhead without the need for an additional interface.

Long lengths

The RGS20 tape scale is available in lengths up to 50 m (contact Renishaw to discuss longer lengths).

Interface option

REE interface

  • Can be used with RGH24B variants only.
  • The REE accepts industry standard 1 Vpp analogue signals which can be interpolated and output as digital RS422 resolution. REE interface
  • Incorporating automatic gain control (AGC) and unique self-tuning adaptive electronics, the REE, combined with the filtering optics of the readhead, ensures excellent signal integrity, and gives improved cyclic error over the all-in-one digital readheads.
  • Please refer to the REE datasheet for further information.

Technical specifications

Measuring standard

Gold plated steel tape with protective lacquer or polyester coating

Readhead size (LxWxH)

36 mm x 13.5 mm x 14.8 mm

Scale pitch

20 μm

Coefficient of thermal expansion

Matched to substrate material when scale ends are fixed with end clamps

Accuracy grade

±15 μm/m (±3 μm/m when 2-point compensation is applied)

Reference mark

Uni-directionally repeatable to 1 unit of resolution with magnetic actuator

Limit switch

Optional single limit (select at time of order)

Scale length

Up to 50 000 mm

Maximum speed



(See data sheet for details)

Up to 4 m/s at -3 dB

Up to 8 m/s

Sub-Divisional Error (SDE)

Typically < ±0.15 μm

Dynamic signal control


Incremental signals



1 Vpp, 12 μA (20 μm period)

Resolutions from 5 μm to 10 nm

Electrical connection

1.5 m, 3 m and 5 m cable lengths with D-type connectors (9 and 15 pin), circular plug (9 pin), flying lead or JST connector.

Power supply

5 V ± 5%, 120 mA (unterminated)

Vibration (operating)

100 m/s2 max @ 55 Hz to 2 000 Hz

Shock (non-operating)

1 000 m/s2, 6 ms , ½ sine

Operating temperature

0 °C to +55 °C


Readhead: IP40

Interface: IP20

Refer to data sheets for full details.



Data sheets

How it works

Within the readhead, an infra-red LED emits light onto the angled scale graduations where it is directed back through a transparent phase grating.

This produces sinusoidal interference fringes at the detection plane within the readhead. The optical scheme averages the contributions from many scale graduations and effectively filters out signals not matching the scale period. This ensures signal stability even when the scale is contaminated or slightly damaged.

Low short-term errors are assured by the unique optical design, typically giving less than ±0.15 μm Sub-Divisional Error (SDE). For even lower SDE and even higher signal stability, the analogue version of the RGH24 can be connected to the REE interface, which include Auto Gain Control (AGC) and Auto Offset Control (AOC) that operates at all speeds.

The RGH24 readhead features a set-up LED, which lights green when optimum installation has been achieved.

A reference mark or a single limit are available with this readhead. The reference mark provides a repeatable home or zero position, whilst the limit is used as an end of travel indicator.

RG2 optical scheme with annotations