Engineering Resources for Motion Control Systems

Insider's Guide: What You Should Know about Rotary Encoders Join the BEI IED mailing list  Email: Ever wondered what features really matter when choosing a rotary optical encoder? This Insider’s Guide shows you the ins and outs of encoder design and what design and specification areas are most important.   Shafts   Covers / Connectors Insider's Guide  2 pgs, 85k   Shaft Seals   Bearings   Optics / Electronics   Environmental & Operational Specifications Shafts Shafts transmit the rotational movement of the device to be monitored into the encoder either directly (hollow-shaft style encoders) or through a flexible coupling (Shafted style of encoders) Inside tip: Look for corrosion resistant shafts and a low TIR (Total Indicated Runout), generally 0.001" or less. hollow-shaft style encoders flexible coupling rotational movement corrosion resistant shaft return to top Shaft Seals Without a shaft seal, the bearings and optical path would be subject to contamination due to dust, dirt and moisture in the environment. Inside tip: A lubricated rotating lip seal provides the best overall environmental protection over the life of the encoder. shaft seal bearings optical path lubricated rotation lip seal environmental shaft seal return to top Optics / Electronics The optics assembly, in conjunction with the electronics, generates a variable amplitude analog signal from the rotation of the code disc and translates it into a digital pulse stream for use by a controller or counter. Inside tip: Electronically centered discs are accurate to better than ±1/40th of a cycle. optics assembly variable amplitude analog signal rotation code disc digital pulse stream return to top Covers / Connectors Covers provide mechanical protection for the internal components of the encoder and seal it against dust and moisture intrusion. Connectors carry the signal through the cover of the encoder body while maintaining environmental protection. Inside tip: All points of entry, including cover screw holes, should be O-ring sealed for the best environmental protection. encoders mechanical internal components environmental protection connectors signal return to top Bearings Bearings, along with the shaft (or shaft tube in the case of a hollow-shaft style of encoder) combine to provide a stable rotational platform which carries the code disc. Inside tip: The most accurate encoders use dual preloaded bearing assemblies. encoders mechanical bearings assemblies shaft hollow-shaft encoder rotational code disc return to top Environmental & Operational Specifications The environmental and operational specifications establish the environment under which the manufacturer feels it is prudent to operate the encoder. Inside tip: Check bearing and temperature ratings carefully. There is no specification standard in the encoder community for these items and if they are critical to your application, you will want to be sure of what you are getting. encoders mechanical bearings environmental temperature ratings operational specification return to top Shafts    |    Shaft Seals    |    Optics    |    Covers    |    Bearings    |    Environmental Specs BEI Motion Control Information   •   Position Sensors   •   1-800-ENCODER (362-6337)   •   Industrial Encoder Automation   •   Signal Conditioners for Encoders M-C-I Home   |   Insider's Guide   |   Glossary   |   Encoder Design Guide   |   Design Calculator  Special Applications  |   Installation Instructions   |  Interpolation Options   |   Notes & Tables   |   News   |   Free Specifying Guide Linear Encoders   |   Tech Support   |   Regulatory Info   |  Resource Links  |   Legal Notice   | Sitemap BEI Sensors   •   7230 Hollister Avenue   •   Goleta, California 93117 Tel: 1-800-ENCODER (362-6337)  •   Fax: 805-968-3154 or 800-960-2726 Trademark     © 2010 BEI Sensors.   All rights reserved. contact webdesigner