Basics of encoders DynAPAR..........................
- 1. 08/07/24 p 1 Encoder Basics #1
- 2. Confidential p 2 Encoder Basics We will be covering: • Common names & definitions • Types • Technology • Mechanical designs • Output • Applications
- 3. Confidential p 3 Different Names for Encoders • Rotopulser • Pulse Generator • Digital Tachometer • Tach • Pulse Tach • Shaft Encoder A lot of names…..
- 4. Confidential p 4 Definitions • Tachometer – Analog device that produces a voltage proportional to speed. • Encoder – Digital device that produces pulses based on rotational position
- 5. Confidential p 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.
- 6. Confidential p 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
- 7. Confidential p 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.
- 8. Confidential p 8 Optical Technology • Utilizes a glass, plastic or metal rotating disc that operates in an light path between a photoelectric transmitter (LED) and receiver.
- 9. 08/07/24 p 9 Encoder Mounting Styles
- 10. Confidential p 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
- 11. Confidential p 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
- 12. Confidential p 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 Flexible Coupling Machined Adapter Bracket
- 13. Confidential p 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
- 14. 08/07/24 p 14 Incremental Outputs Magnetic & Optical
- 15. Confidential p 15 • 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. Encoder Outputs A A Encoder B B
- 16. Confidential p 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. A A Encoder B B
- 17. Confidential p 17 Marker Pulse B A Z Marker Although a “Marker” pulse is standard on some encoders, it is additional feature (charge) on many encoders. Ask for one, if you need one. 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.