Encoder Basics 1 12122021 p 1 Encoder Basics

Encoder Basics #1 12/12/2021 p 1

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

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

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

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 5

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 Confidential NORTHSTAR DYNAPAR & NORTHSTAR HD OPTICAL 6

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 7

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

Encoder Mounting Styles 12/12/2021 p 9

Encoder Basics Mechanical Designs: North. Star: HSD 35, HSD 37, Slim Tach HS 56 • Hollow Shaft – Encoder mounting on shaft extension with bearings and torque arm. • Coupled – Machined face, bracket, stub shaft and a flexible coupling. Dynapar: HS 20 & HS 35 North. Star: RIM 6200, HSD 44 Dynapar: H 56 Rotopulser North. Star: • Bearingless – Frame of encoder bolts to motor, pulse wheel mounts on shaft extension or stub shaft. SLIM Tach: SL 56, SL 85, RL 67 RIM Tach: RIM 8500, RIM 1250 Confidential 10

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 11

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 12

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 13

Incremental Outputs Magnetic & Optical 12/12/2021 p 14

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 15

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 16

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 17