1. Encoder Basics #1
11/8/2018

2. Encoder Basics We will be covering: Common names & definitions Types
Technology
Mechanical designs
Output
Applications
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3. Different Names for Encoders
Rotopulser
Pulse Generator
Digital Tachometer
Tach
Pulse Tach
Shaft Encoder
A lot of names…..
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4. 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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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.
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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
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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.
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8. 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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9. Encoder Mounting Styles
11/8/2018

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
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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
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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
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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
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14. Incremental Outputs
Magnetic & Optical
11/8/2018

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.
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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.
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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.
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