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27 February, 2021

High-vacuum encoders are the `world’s first`

18 July, 2012

Renishaw claims to have developed the world’s first true-absolute encoder readheads that can be used in ultra-high vacuum (UHV) conditions. The linear and rotary encoders, based on the company’s Resolute range, are constructed from vacuum-compatible materials and adhesives that give low out-gassing rates, and have proven clean residual gas analysis (RGA), making them suitable for semiconductor and scientific applications requiring vacuum compatibility to 10-10 Torr.

The encoders offer true-absolute position feedback, with sub-micron accuracy and resolutions to 1nm for both linear and rotary applications. Like standard Resolute encoders, the UHV versions determine position as soon as they are turned on, without needing any movement or battery back-up.

This instant commutation means that, following a power loss, the axes are immediately under complete control, thus eliminating the risk of unchecked movements or collisions. This capability is essential in applications such as wafer handling, where safe extraction of high-value wafers is critical.

Safety is assured by a position-checking algorithm which checks every reading, ensuring that any potential problems are flagged long before they reach the controller. The UHV encoders use pure serial communications with CRC (cyclic redundancy check), eliminating the need for auxiliary 1Vpp signals. They offer high noise immunity, and can detect data corruption.

The encoders are compatible with standard controllers and are available with a wide range of serial protocols, including BiSS, Fanuc, Mitsubishi and Panasonic types.

Because the encoders use a single-track scale code, installations are compact with wide set-up tolerances. The scales are coating-free and can be cleaned and degreased, if required.

Linear scales are available in stainless steel or the ZeroMet low thermal expansion alloy with an accuracy of better than ±1µm on lengths up to 1.13m. Mountings can be self-adhesive, mechanical or on tracks.

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