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RGH34 incremental encoder system with RGS40 linear scale


  • Readhead size: 15 x 15 x 10.5 mm
  • Resolutions to 50 nm
  • Speed up to 8 m/s
  • Analogue or digital outputs


  • Miniature readhead
  • ‘Cut-to-length' scale flexibility
  • Insensitive to dust, light oil and scratches
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What is RGH34?

The RGH34 is a non-contact readhead that offers the performance and reliability of the established RG4 linear encoder system with the versatility of a miniaturised component system. Generous installation tolerances and high-speed, non-contact performance combine with filtering optics to guarantee reliable performance over light oils, dust and scratches. In combination with the RGI interface, the RGH34 system is available with high resolution digital outputs up to 50 nm or with industry standard 1 Vpp analogue output.

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?

Scale flexibility

The RGS40 tape scale is supplied on a reel and can be cut to suit ensuring minimum waste and efficient inventory management.


Designed for OEM applications where a conventional enclosed readhead cannot be fitted, the miniature RGH34 readhead brings reliable performance to size sensitive precision linear and rotary motion applications such as ultra small linear actuators, microscopes and microstages.

Dirt immunity

The RGH34's filtering optics guarantee excellent signal stability in conditions unsuitable for most open, optical encoders.

Technical specifications

Measuring standard

Gold plated steel tape with protective lacquer or polyester coating

Readhead size (LxWxH)

15 mm x 15 mm x10.5 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 limit or reference mark only

Scale length

Up to 50 000 mm

Maximum speed



(See data sheet for details)

Up to 6 m/s at -3 dB

Up to 8 m/s

Sub-Divisional Error (SDE)

Typically <±0.3 µm

Dynamic signal control


Incremental signals




1 Vpp (40 μm period)

Resolutions from 10 μm to 50 nm

Electrical connection

0.05 m, 0.1 m and 0.15 m FPC (Flexible Printed Circuit) cable lengths with low profile zero insertion force micro-connector (10-way)

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


IP00 (System)

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.

The RGH34's companion interface, the RGI34, 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.

RG4 optical scheme with annotations