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High-spec optical encoders have built-in signal processing

15 July, 2016

The UK metrology specialist, Renishaw, has announced a family of compact, accurate digital incremental encoders with interpolation and digital signal processing built into their readheads, thus eliminating the need for external interfaces. The company says that the Vionic optical encoders deliver the highest performance that it has ever offered in an incremental encoder system.

The encoders combine filtering optics with a new custom interpolation and monitoring Asic (application-specific integrated circuit) that enhances dynamic signal processing and improves signal stability.

The encoders have been designed to minimise size, while delivering class-leading performance in terms of cyclic error, jitter and accuracy. There are two variants. The standard Vionic readhead offers a sub-divisional error (SDE) of <±30nm, resolutions from 5µm to 20nm, and speeds beyond 12 m/s. For the most demanding applications, the Vionicplus version offers an SDE of <±10nm, jitter of 1.6nm rms and resolutions from 2.5–100nm. Low-SDE encoders are essential to minimise velocity ripple, which is important in constant-velocity applications, such as laser scanning.

The new encoders are available with the same linear and rotary (angle) scale ranges as Renishaw’s Tonic series, allowing users to install them as drop-in replacements. Available scale types include metal tape, spar, and rotary rings. The scales come with user-selectable In-Trac reference marks embedded in the incremental channel, and dual-limit switches in the case of linear scales.

Renishaw's tiny digital encoders incorporate signal processing in their readheads

Installation is said to be easy using a diagnostic tool that includes software for controlling and monitoring the set-up and calibration routines. The software offers enhanced graphics, automatically generated plots of signal strength vs position, Lissajous plots, DRO output, and readhead pitch indication. It can be installed on production lines to allow remote calibration.

The Vionic encoders will be available to order from August 2016. 

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