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RGH41 incremental encoder system with RGS40 linear scale


  • Readhead size: 44 x 27 x 17 mm
  • Resolutions to 50 nm
  • Speed up to 15 m/s
  • Analogue or digital outputs


  • Easy to install
  • Digital RS422 output direct from the readhead
  • Dual end of travel limit switches
  • Scale lengths available up to 50 m  (>50 m special order only)
  • ‘Cut-to-length' scale flexibility
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What is RGH41?

The RGH41 readhead offers all the benefits of the market proven RG4 linear encoder system - generous installation tolerances and high-speed, non-contact performance with filtering optics to guarantee reliable performance over light oils, dust and scratches.

What is RGS40 scale?

RGS40 is a tape scale manufactured from a thin flexible steel strip, featuring a 40 µm pitch, which is gold plated to give high reflectivity and corrosion resistance. It may be mounted using UHV compatible adhesive backing tape, to most engineering materials, including metals, ceramics and composites. Secured to the substrate with scale end-clamps, RGS40 is mastered to the substrate and will match the substrates 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?

Ease of setup

With generous setup tolerances and an integral setup LED offering real-time signal feedback, the RGH41 readhead can be installed quickly and easily.

Dual limit sensing

The RGH41 readhead comes with single or dual limit sensing as standard. The limits enable dedicated signals for each end-of-axis indication. A repeatable reference or datum mark also comes as standard.

Direct output

The RGH41 outputs RS422 digital resolutions from 10 µm to 50 nm direct from the readhead without the need for an additional interface.

Long lengths

The RGS40 tape scale is available in lengths up to 50 m (contact Renishaw to discuss longer lengths).

Interface option

REE interface

  • Can be used with RGH41A and B 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)

44 mm x 27 mm x 17 mm

Scale pitch

40 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 switches

Single or dual limits depending on readhead option

Scale length

Up to 50 000 mm

Maximum speed



(See data sheet for details)

Up to 8 m/s at -3 dB

Up to 15 m/s

Sub-Divisional Error (SDE)

Typically < ±0.3 μm

Dynamic signal control

DC light servo provides simple Auto Gain Control (AGC) function to optimise signal level

Incremental signals




1 Vpp (40 μm period)

Resolutions from 10 μm to 50 nm

Electrical connection

0.5 m, 1 m, 1.5 m, 3 m and 5 m cable lengths with D-type connector (15 pin), circular plug (12 pin), in-line connector (16 pin) or flying lead

Power supply

5 V ± 5%, 120 mA (typical), 175 mA (0.4 μm, 0.2 μm, 0.1 μm and 50 nm resolutions) (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



Refer to data sheets for full details.



Data sheets

Technical drawings

How it works

Within the readhead, an infra-red LED emits light laterally onto the flat top graduations of the scale, creating a ‘side lit' arrangement as shown in the optical diagram

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 ±0.30 μm Sub-Divisional Error (SDE). For even lower SDE and even higher signal stability, the analogue version of the RGH41 can be connected to the REE interface, which include Auto Gain Control (AGC) and Auto Offset Control (AOC) that operates at all speeds.

The RGH41 readhead features a set-up LED, which lights green when optimum installation has been achieved.

Reference mark and dual limits are available with this readhead. The reference mark provides a repeatable home or zero position, whilst the limits are used as end of travel indicators.

RGH41 optical scheme with annotations