Encoder-Basics how encoder works types mechanism

Encoder

1. 5/29/2024 p 1
Encoder Basics #1

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

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

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

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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.

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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

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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.

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

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Encoder Mounting Styles

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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

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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

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Coupled Encoders
•Highest installationcost.
–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

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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

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Incremental Outputs
Magnetic & Optical

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•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 OutputsA
A
Encoder
B
B

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Single Output, Quadrature Signal with Complements
•Signal A leads B in one direction, B leads Ain 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

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Marker PulseB
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.