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Encoder Basics #1

Encoder Basics #1. Encoder Basics. We will be covering: Common names & definitions Types Technology Mechanical designs Output Applications. Different Names for Encoders. Rotopulser Pulse Generator Digital Tachometer Tach Pulse Tach Shaft Encoder A lot of names…. Definitions.

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Encoder Basics #1

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  1. Encoder Basics #1

  2. Encoder Basics We will be covering: • Common names & definitions • Types • Technology • Mechanical designs • Output • Applications Confidential

  3. Different Names for Encoders • Rotopulser • Pulse Generator • Digital Tachometer • Tach • Pulse Tach • Shaft Encoder A lot of names….. Confidential

  4. Definitions • Tachometer– Analog device that produces a voltage proportional to speed. • Encoder– Digital device that produces pulses based on rotational position Confidential

  5. Encoder Basics Encoder Types: • Incremental • Provides identical electronic pulses at each division of shaft rotation. • Used for speed or velocity control of motors • Absolute • Provides a unique electronic piece of information at each division of shaft position. • Used for positioning systems • Resolver • Provides sine wave and cosine wave to provide both velocity and position feedback. Confidential

  6. Encoder Basics Sensing Technologies: • Magnetic (Magneto-resistive) • Tough and simple • Heavy Duty enough for Mills • No Optics (no glass breakage) • Limited to 2048 PPR • Optical • Higher Resolution (up to 10,000 PPR) • Better signal quality • Shafted and Hollow shaft designs NORTHSTAR DYNAPAR & NORTHSTAR HD OPTICAL Confidential

  7. Magneto-Resistive Technology • Features a magnetic pulse wheel that is imprinted with numerous, small magnetic poles. • Rotation of the magnetic pulse wheel creates an alternating pattern of north-south magnetic fields for the pick-up head. • The electrical circuit in the sensor produces digital pulses proportional to motor speed. Confidential

  8. Optical Technology • Utilizes a glass, plastic or metal rotating disc that operates in an light path between a photoelectric transmitter (LED) and receiver. Confidential

  9. Encoder Mounting Styles

  10. Encoder Basics Mechanical Designs: • Hollow Shaft • Encoder mounting on shaft extension with bearings and torque arm. • Coupled • Machined face, bracket, stub shaft and a flexible coupling. • Bearingless • Frame of encoder bolts to motor, pulse wheel mounts on shaft extension or stub shaft. NorthStar: HSD35, HSD37, Slim Tach HS56 Dynapar: HS20 & HS35 NorthStar: RIM 6200, HSD44 Dynapar: H56 Rotopulser NorthStar: SLIM Tach: SL56, SL85, RL67 RIM Tach: RIM8500, RIM1250 Confidential

  11. Hollow Shaft Encoders • The lowest cost encoder to install • No couplings to align or isolate • No adapter (flower pot) • No machined fan cover required on TEFC motors • Flexible torque arm • Allow encoder to ride freely on shaft extension • If too rigid, provide stress on encoder bearings • Arm must be isolated from motor to avoid motor shaft currents from damaging encoder bearings • Ideal for Reliance TEFC V*S Master motors • Good for all motor enclosures Confidential

  12. Coupled Encoders • Highest installation cost. • Requires a expensive, flexible coupling • Requires adapter (flower pot) between encoder and motor • On larger motors, an expensive insulated coupling may be required to protect Coupled Encoder bearings • V*S Master TEFC motors requires a special cast iron machined fan cover Machined Adapter Bracket Flexible Coupling Confidential

  13. Bearingless Encoders • Less space required • No couplings to align or isolate • Can have a thru shaft • Can be mounted between brake and motor • Can be mounted on drive or non-drive end • No bearings to fail! • Pulse wheel mounted directly on shaft extension • Encoder housing bolted to motor bracket • No concerns with motor currents damaging bearings • Ideal for Reliance RPM-AC and DC motors • Good to mount between brake and motor bracket on TENV, DPFV and TEBC-PB enclosures • Not recommended for V*S Master motors Confidential

  14. Incremental Outputs Magnetic & Optical

  15. Encoder Outputs • Incremental encoders are usually supplied with two channels (A & B) that are offset by 90 degrees. • If complements are included (A, B ), the signal is “quadrature”, providing speed of rotation AND direction of rotation. Confidential

  16. Single Output, Quadrature Signal with Complements • Signal A leads B in one direction, B leads A in the reverse direction • Complement pulses, A and B are used to provide electrical noise immunity for the signal as it travels through the cable. Confidential

  17. Marker Pulse A marker pulse (reference, index or Z pulse) is a once per revolution pulse that occurs at precisely the same mechanical point in a 360º revolution of the encoder shaft. Although a “Marker” pulse is standard on some encoders, it is additional feature (charge) on many encoders. Ask for one, if you need one. Confidential

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