Apex Metrology - cmm and metrology equipment uk

Apex Metrology - cmm and metrology equipment uk

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Encoders

Encoders

The RG2 is an open, non-contact optical linear encoder system, eliminating friction and wear whilst permitting reliable high speed, high resolution operation. The unique 20 µm pitch optics ensure excellent signal stability in conditions considered unsuitable for most open optical linear encoders.

Available with 20 µm analogue signal period or digital resolutions from 5 µm to 10 nm. All RG2 linear encoder systems incorporate a unique, integral set-up LED, which lights green when optimum installation has been achieved. Reference mark and/or limit switch outputs are available on all models of readhead. The reference mark provides a repeatable home or zero position, whilst the limit is used as an end of travel indicator. The RGH22 has a dual-limit option, which gives a unique output for each end of travel.

An infra-red LED emits light onto the angled scale facets where it is directed back into the readhead 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 facets and effectively filters out signals not matching the scale period. This ensures signal stability even when the scale is contaminated or slightly damaged.

Thermal characteristics often play a significant role in determining overall measurement accuracy. The RGS20-S tape scale is rigidly restrained at its ends and is therefore forced to match the thermal behaviour of the substrate, removing the need to compensate for yet another coefficient of expansion.

Low short-term errors are assured by the unique optical design, typically giving less than ±0.15 µm cyclic error (or sub-divisional error). This is included within the linearity specification of ±0.75 µm in 60 mm or ±3 µm in any metre length.

RG2 readheads offer a durable scale with excellent metrology that can be cut to any length. RGS20-S gold plated tape scale is lacquer coated and requires none of the careful handling and cleaning most traditional scales need. A self-adhesive backing enables quick and easy installation with a range of applicators to suit the readhead type. To complete the installation, reference mark, limit switch actuators, and end clamps are simply glued into place.

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