What is an Encoder?
An
encoder
is a sensor of mechanical motion that generates digital signals in
response to motion. As an electro-mechanical device, an encoder is able
to provide motion control system users with information concerning
position, velocity and direction. There are two different types of
encoders: linear and
rotary.
A linear encoder responds to motion along a path, while a rotary
encoder responds to rotational motion. An encoder is generally
categorized by the means of its output. An incremental encoder
generates a train of pulses which can be used to determine position and
speed. An absolute encoder generates unique bit configurations to track
positions directly.
Block Diagram for Encoders
Basic Types of Encoders
Linear and rotary encoders are broken
down into two main types: the absolute encoder and the incremental
encoder. The construction of these two types of encoders is quite
similar; however they differ in physical properties and the
interpretation of movement.
Incremental Encoder
Single-Ended Encoder
An Incremental rotary encoder is also referred to as a quadrature encoder. This type of encoder utilizes sensors that use
optical, mechanical or
magnetic index counting for angular measurement.
How do Incremental Encoders Work?
Incremental rotary encoders
utilize a transparent disk which contains opaque sections that are
equally spaced to determine movement. A light emitting diode is used to
pass through the glass disk and is detected by a photo detector. This
causes the encoder to generate a train of equally spaced pulses as it
rotates. The output of incremental rotary encoders is measured in
pulses per revolution which is used to keep track of position or
determine speed.
A single-channel
output is commonly implemented in applications in which direction of
movement is not significant. Instances in which direction sensing is
important, a 2-channel, quadrature, output is used. The two channels, A
and B, are commonly 90 electrical degrees out of phase and the
electronic components determine the direction based off the phase
relationship between the two channels. The position of an incremental
encoder is done by adding up all the pulses by a counter.
A setback of the incremental encoder is count loss which occurs
during power loss. When restarting, the equipment must be referenced to
a home position to reinitialize the counter. However, there are some
incremental encoders, like those sold at Anaheim Automation, which come
equipped with a third channel called the index channel. The index
channel produces a single signal pulse per revolution of the encoder
shaft and is often used as a reference marker. The reference marker is
then denoted as a starting position which can resume counting or
position tracking.
NOTE: Incremental rotary encoders are not as accurate as
absolute rotary encoders due to the possibility of interference or a
misread.
Absolute Encoder
An absolute encoder
contains components also found in incremental encoders. They implement
a photodetector and LED light source but instead of a disk with evenly
spaced lines on a disc, an absolute encoder uses a disk with concentric
circle patterns.
How do Absolute Encoders Work?
Absolute encoders utilize stationary mask in between the
photodetector and the encoder disk as shown below. The output signal
generated from an absolute encoder is in digital bits which correspond
to a unique position. The bit configuration is produced by the light
which is received by the photodetector when the disk rotates. The light
configuration received is translated into gray code. As a result, each
position has its own unique bit configuration.
Linear Encoder
A linear encoder is
a sensor, transducer or reading-head linked to a scale that encodes
position. The sensor reads the scale and converts position into an
analog or digital signal that is transformed into a digital readout.
Movement is determined from changes in position with time. Both optical
and magnetic linear encoder types function using this type of method.
However, it is their physical properties which make them different.
How do Optical Linear Encoders Work?
The light source and lens produce a parallel beam of light which
pass through four windows of the scanning reticle. The four scanning
windows are shifted 90 degrees apart. The light then passes through the
glass scale and is detected by photosensors. The scale then transforms
the detected light beam when the scanning unit moves. The detection of
the light by the photosensor produces sinusoidal wave outputs. The
linear encoder system then combines the shifted signals to create two
sinusoidal outputs which are symmetrical but 90 degrees out of phase
from each other. A reference signal is created when a fifth pattern on
the scanning reticle becomes aligned with an identical pattern on the
scale.
How does a Linear Encoder Work?
A Linear Encoder system uses a magnetic sensor readhead and a
magnetic scale to produce TTL or analog output for Channel A and B. As
the magnetic sensor passes along the magnetic scale, the sensor detects
the change in magnetic field and outputs a signal. This output signal
frequency is proportional to the measuring speed and the displacement of
the sensor. Since a linear encoder detects change in the magnetic
field, the interference of light, oil, dust, and debris have no effect
on this type of system; therefore they offer high reliability in harsh
environments.
A magnetic encoder
consists of two parts: a rotor and a sensor. The rotor turns with the
shaft and contains alternating evenly spaced north and south poles
around its circumference. The sensor detects these small shifts in the
position N>>S and S>>N. There many methods of detecting
magnetic field changes, but the two primary types used in encoders are:
Hall Effect and Magneto resistive. Hall Effect sensors work by detecting
a change in voltage by magnetic deflection of electrons. Magneto
resistive sensors detect a change in resistance caused by a magnetic
field.
Hall-Effect sensing
The Sensor produces and processes Hall-Effect signals producing a
quadrature signal as is common with optical encoders. The output is
generated by measuring magnetic flux distributions across the surface of
the chip. The output accuracy is dependent on the radial placement of
the IC with respect to the target magnet. The chip face should be
parallel to the magnet so the magnet to sensor air gap is consistent
across the sensor face.
Magnetic encoders avoid the three vulnerabilities that optical encoders face:
• Seal failures which permit the entry of contaminents
• The optical disk may shatter during vibration or impact
• Bearing failures
Magnetic devices designed effectively eliminate the first two
failure modes and offer an opportunity to reduce bearing failures as
well. Magnetic encoders do not make errors due to contamination because
their sensors detect variations in magnetic fields imbedded in the rotor
and oil, dirt and water do not affect these magnetic fields.
Hall-Effect sensors
generally have lower cost and are less precise than magnetic resistive
sensors. This means that Hall-Effect sensors, when used in an encoder
produce more "jitter", or error in the signal caused by sensor
variations.
Commutation Encoders
A commutation encoder
contains the same fundamental components as incremental encoders but
with the addition of commutation tracks alongside the outer edge of the
disk for U/V/W output.
How do Commutation Encoders Work?
Commutation encoders
utilize a transparent disk which includes opaque sections that are
equally spaced to determine movement. A light emitting diode is used to
pass through the glass disk and is detected by a photo detector. This
causes the encoder to generate a train of equally spaced pulses as it
rotates. The output of incremental rotary encoders is measured in
pulses per revolution which is used to keep track of position or
determine speed.
The outer part of the encoder disk includes commutation tracks which
provide a controller with information on the exact position of the motor
poles, so that the proper controller input can be supplied to the
motor. The commutation tracks of the encoder read the motor position
and instruct the controller as to how to provide efficient and proper
current to the motor to cause rotation. Commutation output for U/V/W
can be in the form of differential output or open-collector
(manufacturer dependent).
How are Encoders Controlled?
Encoders are controlled through the rotation
the shaft it is mounted to. The shaft comes into contact with a hub
which is in internal to the encoder. As the shaft rotates, it causes
the disc, with both transparent and solid lines, to rotate across the
circuitry of the encoder. The circuitry of the encoder contains an LED
which is captured by a photoelectric diode and outputs pulses to the
user. The speed at which the disc rotates will be dependent on the speed
of the shaft the encoder is connected to. Anaheim Automation's
optical and
magnetic encoder lines are powered from a single +5VDC power source, and is able to sing and source 8mA each.
Physical Properties
Linear Encoders
The key components
of a linear encoder are a scanning unit, sensor, transducer or readhead,
paired with a transmissive or reflective scale, which encodes position.
The scale of a linear encoder is generally made of glass and mounted
to a support and the scanning unit contains a light source, photocells,
and a second glass piece called the scanning reticle. Collectively, the
linear encoder is able to convert motion into digital or analog signals
to determine the change in position over time.
The key components of a
rotary encoder
are the disk, light sources and detectors, and electronics. The disk
contains a unique pattern of concentric etched circles and alternates
between opaque and transparent segments. This pattern provides unique
bit configurations and is used to assign specific positions. For every
concentric ring in a rotary encoder, there is a light source and light
detector which identify lines etched on the disk. The electronics
consist of an output device which takes the signal obtained from the
sensor (light/detector source) to provide feedback of position and/or
velocity. All of these components are enclosed in a single housing
unit.
Differential-Type Encoder
The key components of an
incremental encoder
are a glass disk, LED (light emitting diode), and a photo detector.
The transparent disk contains opaque sections which are equally spaced
to deflect light while the transparent sections allow light to be passed
through shown in Figure 2 below. An optical encoder utilizes a light
emitting diode which shines light through the transparent portions of
the disk. The light that shines through is received by the photo
detector which produces an electrical signal output.
Where are Encoders Used?
Encoders have become a vital source for
many applications requiring feedback information. Whether an
application is concerned with speed, direction or distance, an encoders
vast capability allow users to utilize this information for precise
control. With the emergence of higher resolutions, ruggedness, and
lower costs, encoders have become the preferred technology in more and
more areas. Today, encoder applications are all around us. They are
utilized in printers, automation, medical scanners, and scientific
equipment.
Anaheim Automation’s cost-effective
encoder
product line is a wise choice for applications requiring feedback
control. Anaheim Automation’s customers for the encoder product line is
diverse: industrial companies operating or designing automated
machinery involving food processing, labeling, cut-to-length
applications, conveyor, material handling, robotics, medical
diagnostics, and CNC machinery.
Encoders are used in Many Industries
Encoders have become an essential component to applications in
many different industries. The following is a partial list of
industries making use of encoders:
• Automotive – The automotive industry utilize encoders as sensors of mechanical motion may be applied to controlling speed.
• Consumer Electronics and Office Equipment – In the consumer
electronics industry, encoders are widely used office equipment such as
PC-based scanning equipment, printers, and scanners.
• Industrial – In the industrial industry, encoders are used in
labeling machines, packaging and machine tooling with single and
multi-axis motor controllers. Encoders can also be found in CNC machine
control.
• Medical – In the medical industry, encoders are utilized in
medical scanners, microscopic or nanoscopic motion control of automated
devices and dispensing pumps.
• Military - The military also utilizes encoders in their application of positioning antennas.
• Scientific Instruments – Scientific equipment implement encoders in the positioning of an observatory telescope.
Applications for Encoders
An encoder can be used in applications
requiring feedback of position, velocity, distance, etc. The examples
listed below illustrate the vast capabilities and implementations of an
encoder:
• Robotics
• Labeling Machines
• Medical Equipment
• Textiles
• Drilling Machines
• Motor Feedback
• Assembly Machines
• Packaging
• X and Y Indication Systems
• Printers
• Testing Machines
• CNC Machines
How to Select an Encoder
There are several important criteria involved in selecting the proper encoder:
1. Output
2. Desired Resolution (CPR)
3. Noise and Cable Length
4. Index Channel
5. Cover/Base
Output
The output is dependent on what is required by the application.
There are two output forms which are incremental and absolute.
Incremental output forms take form of squarewave outputs. For an
application requiring an incremental encoder, the output signal is
either zero or the supply voltage. The output of an incremental encoder
is always a squarewave due to the switching of high (input voltage
value) and low (zero) signal value. Absolute encoders operate in the
same manner as incremental encoders, but have different output methods.
The resolution of an absolute encoder is described in bits. The output
of absolute encoders is relative to its position in a form of a digital
word. Instead of a continuous flow of pulses as seen by incremental
encoders, absolute encoders output a unique word for each position in
form of bits. Equivalent to 1,024 pulses per revolution, an absolute
encoder is described to have 10 bits (210 = 1024).
Desired Resolution (CPR)
The resolution of incremental encoders is frequently described
in terms of cycles per revolution (CPR). Cycles per revolution are the
number of output pulses per complete revolution of the encoder disk.
For example, an encoder with a resolution of 1,000 means that there are
1,000 pulses generated per complete revolution of the encoder.
Noise and Cable Length
When selecting the proper encoder for any application, the user
must also take into account noise and cable length. Longer cable
lengths are more susceptible to noise. It is crucial to use proper
cable lengths to ensure the system functions correctly. It is
recommended to use shielded, twisted-pair cables with preferably low
capacitance value. The rating for capacitance value is normally in
capacitance per foot. The importance of this rating is for well defined
squarewave pulse outputs from the encoder rather than “jagged” or
“saw-toothed” like pulses due to the interference of noise.
Index Channel
The index channel is an optional output channel which provides a
once per revolution output pulse. This pulse allows for the user to
keep track of position and establishes a reference point. This output
channel is extremely valuable for incremental encoders when an
interruption of power occurs. In instances with a power failure, the
last sustained index channel can be used as a reference marker for a
restarting point. Therefore, when such an occurrence takes place, an
index channel can prove to be quite valuable in applications utilizing
incremental encoders. Absolute encoders do not have an issue with losing
track of position in power loss situations, because every position is
assigned a unique bit configuration.
Cover/Base
Cover and base options are considerations for specific
application requirements. Enclosed cover options help protect the
encoder from dust particles. Base options play a significant role in
large vibration environments. Such mounting options are transfer
adhesives which stick directly on the back of the encoder to the
mounting surface, molded ears for direct mounting. Anaheim Automation
also offers various base options for mounting purposes.
Anaheim Automation offers a selection of cover and base options to meet your application needs.
Cover Options:
E-Option: Enclosed Cover H-Option: Hole Diameter
Base Options:
3-Option: All five Hole diameters become .125 A-Option: Adds Alignment Shoulder
G-Option: Molded Ears R-Option: 3-slot Adapter Plate T-Option: Transfer Adhesive
How to Install an Encoder
After selecting the
appropriate motor, it is important to know how to properly install it.
The installation of each encoder is dependent upon its mounting or base
option. If an encoder is to be mounted to a motor shaft, then a
centering tool can be used to align the hole of the encoder to the
shaft. The different mounting options have varying functionalities. An
R-option allows for a +/- 15 degree play of motion in which the encoder
can rotate back and forth. A T-Option however, uses adhesive to stick
to the back of a motor.
For step by step instructions on installing an Anaheim Automation encoder, watch our video tutorials
here. Anaheim Automation also provides the option of an
encoder adder, where we mount the encoder for you, hassle free!
Advantages of an Encoder
- Highly reliable and accurate
- Low-cost feedback
- High resolution
- Integrated electronics
- Fuses optical and digital technology
- Can be incorporated into existing applications
- Compact size
Disadvantages of an Encoder
- Subject to magnetic or radio interference (Magnetic Encoders)
- Direct light source interference (Optical Encoders)
- Susceptible to dirt, oil and dust contaminates
PLEASE NOTE: Technical assistance
regarding its Encoder line, as well as all the products manufactured or
distributed by Anaheim Automation, is available at no charge. This
assistance is offered to help the customer in choosing Anaheim
Automation products for a specific application. However, any selection,
quotation, or application suggestion for an Encoder, or any other
product, offered from Anaheim Automation’s staff, its' representatives
or distributors, are only to assist the customer. In all cases,
determination of fitness of the custom Encoder in a specific system
design is solely the customers' responsibility. While every effort is
made to offer solid advice regarding the Encoder product line, as well
as other motion control products, and to produce technical data and
illustrations accurately, such advice and documents are for reference
only, and subject to change without notice.
Problem: No output
Solution: No output may be a result of various factors. Steps
can be taken to ensure the proper functionality of the encoder. No
mechanical movement results in any signal being output from the encoder.
To correct this issue, observe if the encoder is rotating. Verify all
wring between the encoder and the driver/controller is correct and the
appropriate voltage supply is used. Having loose connections or
improper voltage supply may not allow the encoder to function properly.
Finally, ensure the correct signal type (e.g. open collector, pull-up,
line driver or push-pull) is being used for your application. If the
problem persists, swap encoders, if possible, to determine if the
encoder is the issue.
Problem: Unable to find index pulse
Solution: The index pulse, or reference marker, is a once per
revolution output of an encoder and is best found using an oscilloscope.
Verify all the wiring between the encoder and the driver/controller is
correct and the appropriate voltage supply is used. If that does not
solve the issue, try lowering the RPM of the motor, as the
driver/controller may not be able to identify the index pulse at very
high RPM values.
Problem: Count output indicates incorrect direction
Solution: If the count output indicates an incorrect direction
then check for the wire configuration. See if any wires are reversed.
If they are reversed, simply swap wires.
NOTE: If your application is using index, reversing the wire
configuration causes the reference alignment to also change. If so,
please make the appropriate changes to your application.
Problem: Encoder is not rotating
Solution: When encoders are exposed in open environments, dust
and debris particles may accumulate around the shaft. Simply clean the
exposed area and ensure that there are not objects obstructing the
encoder from rotating.
Problem: Noise Interference
Solution: To improve the noise immunity of encoders it is
strongly advised that no other electrical equipment be nearby or be kept
at a fair distance. Encoder cables should also be shielded and proper
wires should be grounded to minimize electrical noise.
Problem: Distorted or incorrect output
Solution: Distorted or incorrect output can be any combination of
loose wiring connections, encoder output not compatible with
driver/controller, electrical noise or improper alignment. Check for
wire connections, compatibility issues with the encoder and the
driver/controller, alignment of the encoder and the shaft to solve this
issue.
The relationship between the encoder CPR frequency and the speed of the motor (RPM) is given by the following equation:
f = (cycles/rev)*(rev/sec)/1000 = kHz
RPM = Revolution per Minute
CPR = Cycles per Revolution
Distance Conversion:
(PPR) / (2*pi*radius of shaft) = pulses per inch
(Pulses per inch)^-1 = inch per pulse
Absolute Encoder - provides the
shaft position in a bit configuration and is able to maintain or provide
absolute position even after instances of power loss/failure.
Accuracy – difference in distance between the theoretical and the actual position.
Cycles Per Revolution (CPR) - Cycles per revolution are the number of output pulses per complete revolution of the encoder disk
Encoder - is a sensor of mechanical motion that generates digital signals in response to motion.
Incremental Encoder
- device that provides a train of pulses due in response to mechanical
motion. The output of this encoder is in form of a squarewave.
Index - a separate output channel which provides a single pulse per shaft revolution. It can be used to
establish a reference or marker for a starting position.
Interpolation - is the method of increasing the resolution of
an encoder. This method allows for the encoder to produce a higher
resolution output without increasing the overall size of the disk and
encoder.
Line Driver - is a sourcing output. This means that when in
‘ON’ state the line driver will supply Vcc and in the ‘OFF’ state the
driver will float. A sinking input is required for line driver
applications.
Open Collector - is a sinking output. In the ‘OFF’ state, an
open collector will be grounded and in the ‘ON’ state, the open
collector will float. A sourcing input is required for open collector
applications.
Pulses Per Revolution (PPR) - the total number of pulses produced per full revolution of the encoder shaft.
Push-pull - is a combination between a line driver and an open
collector. In the ‘OFF’ state it will be grounded and in the on ‘ON’
state it will supply Vcc.
Quadrature Encoder - two output channels which are out of phase
by 90 electrical degrees. From the phase difference, the direction of
rotation can also be determined.
Resolution – number of line increments on a disk. Resolution
for incremental encoders is often referred to as cycles per resolution
and for absolute encoders it is in terms of bits.
Single Channel Encoder – has only one output channel and is used in speed applications.
Squarewave - a repetitive waveform corresponding to high and low signals.
1. What are single output channel incremental encoders used for?
A. Sense Direction
B. Sense Speed (Tachometers)
C. Position Feedback
2. Which of the following is a NOT difference between absolute and an incremental encoder?
A. Absolute encoders provide a unique position.
B. Absolute utilize concentric circles on a transparent disc while
incremental encoders utilize evenly spaced opaque sections to determine
movement.
C. Both absolute encoders and incremental encoders lose position due to power loss/failure.
3. Which of the following applies to an Index Channel?
A. Position Tracker
B. Reference/ Homing Point
C. Determining Distance
D. All of the Above
4. What does an Encoder do?
A. Senses mechanical motion.
B. Provides information concerning position, velocity and direction.
C. Converts analog into digital information.
D. None of the above.
E. All of the above.
5. What does CPR stand for?
A. Cycles per Revolution
B. Counts per Revolution
C. Both A and B
D. None of the above.
6. Describe the different types of encoder outputs below.
TTL - are logic gate
circuits designed to input and output two types of signal states: high
(1) and low (0). The transition between high and low signals generates
TTL squarewave outputs.
Open Collector - is a sinking output. In the ‘OFF’ state, an open
collector will be grounded and in the ‘ON’ state, the open collector
will float. A sourcing input is required for open collector
applications.
Line Driver - is a sourcing output. This means that when in ‘ON’
state the line driver will supply Vcc and in the ‘OFF’ state the driver
will float. A sinking input is required for line driver applications.
Push-Pull - is a combination between a line driver and an open
collector. In the ‘OFF’ state it will be grounded and in the on ‘ON’
state it will supply Vcc.
7. Which of the following are encoder advantages?
A. Low cost
B. High resolution
C. High reliability and accuracy
D. Compact size
E. Integration between optical and digital technology
F. All of the Above
8. Quadrature channels are out of phase by how many electrical degrees?
A. 45
B. 120
C. 60
D. 90
9. List the criteria for selecting an encoder:
1. Output
2. Desired Resolution (CPR)
3. Noise and Cable Length
4. Index Channel
5. Cover/Base
10. Calculation: If an encoder has a
resolution of 1024 and is mounted to a shaft of diameter 1”, what will
be the pulses per inch and inch per pulse with this combination?
(1024*4)/(2*pi*.5) = 1303.79 pulses per inch
(1303)^-1 = .000767 inch per pulse
Q: What is an encoder?
A: An encoder is a sensor of mechanical motion that generates digital signals in response to motion.
Q: How do you install an Encoder?
A: For step by step tutorials on how to install Anaheim Automation’s encoders,
click here.
Q: What is the difference between absolute and incremental encoders?
A: Absolute and incremental encoders are different in two ways:
- Every position of an absolute encoder is unique
- An absolute encoder never loses its position due to power loss
or failure. Incremental encoders lose track of position upon power loss
or failure
Q: What is a channel?
A: A channel is an electrical output signal from an encoder.
Q: What is a quadrature?
A: A quadrature has two output channels, with repeating
squarewaves, which are out of phase by 90 electrical degrees. From the
phase difference, the direction of rotation can also be determined.
Q: What is an index pulse?
A: The index pulse, also referred to as a reference or marker pulse, is a single output pulse produced once per revolution.
Q: What other types of encoder technologies are there?
A: There are two types of encoder technologies.
- Optical: This type of technology uses a light shining into a photodiode through slits in a metal/glass disk.
- Magnetic: Strips of magnetized material are placed on rotating
discs and are sensed by Hall-Effect Sensors or magneto-resistive
sensors.
Q: What types of applications are encoders implemented in?
A: They are frequently utilized in
stepper motors, automation, robotics, medical devices, motion control and many other applications requiring position feedback.
Q: Does any encoder disk (codewheel) work with any encoder module?
A: No, each resolution and each disk diameter works with a different encoder module.
Q: What is PPR?
A: PPR stands for pulse per revolution in rotational motion for
rotational motion and pulse per inch or millimeter for linear motion.
Q: When can a single output channel be used in an incremental encoder?
A: A single output channel for an incremental encoder can be
used when it is not important to sense direction. Such applications
make use of tachometers.
Q: Will Anaheim Automation mount an encoder to motors?
A: Yes, a special part number would be created for including the encoder attached to a motor.
Required Maintenance
Encoders require very little maintenance due
to their ruggedness and reliability. However, it is recommended to
minimize an encoders exposure to dust particles or debris and also,
unless designed for exposure to water or moisture. Also, under duress
of shock and vibrations, encoder discs may become scratched resulting in
encoder failure. If such an event occurs, the disc may need to be
replaced to provide accurate readings.
Environmental Considerations for an Encoder
The following environmental and safety
considerations must be observed during all phases of operation, service
and repair of an encoder. Failure to comply with these precautions
violates safety standards of design, manufacture and intended use of an
encoder. Please note that even with a well‐built encoder, products
operated and installed improperly can be hazardous. Precaution must be
observed by the user with respect to the load and operating environment.
The customer is ultimately responsible for the proper selection,
installation, and operation of the encoder.
The atmosphere in which an encoder is used must be conducive to good
general practices of electrical/electronic equipment. Do not operate
the encoder in the presence of flammable gases, dust, oil, vapor or
moisture. For outdoor use, the encoder must be protected from the
elements by an adequate cover, while still providing adequate air flow
and cooling. Moisture may cause an electrical shock hazard and/or
induce system breakdown. Due consideration should be given to the
avoidance of liquids and vapors of any kind. Contact the factory should
your application require specific IP ratings. It is wise to install
the encoder in an environment which is free from condensation, dust,
electrical noise, vibration and shock.
Additionally, it is preferable to work with encoders in a non‐static,
protective environment. Exposed circuitry should always be properly
guarded and/or enclosed to prevent unauthorized human contact with live
circuitry. No work should be performed while power is applied. Don’t
plug in or unplug the connectors when power is ON. Wait for at least 5
minutes before doing inspection work on the encoder after turning power
OFF, because even after the power is turned off, there will still be
some electrical energy remaining in the internal circuit of the encoder
circuitry.
Plan the installation of the encoder in a system design that is free
from debris, such as metal debris from cutting, drilling, tapping, and
welding, or any other foreign material that could come in contact with
the circuitry. Failure to prevent debris from entering the encoder can
result in damage and/or shock.
Lifetime of an Encoder
The lifetime of an encoder is dependent on
various factors such as environmental exposure and application use. By
limiting the exposure of the encoder to electrical equipment,
temperatures above recommended values, condensation, and vibration and
shock, and using the encoder as directed by the manufacturer can extend
the lifetime of an encoder.
Along with the encoder line, Anaheim Automation carries a comprehensive line of single-ended and differential
encoder cables
with four, six, and eight leads, cable lengths up to 16 feet, and
encoder centering tools. Additionally, Anaheim Automation offers an
extended line of
stepper,
brushless, and
servo motors which can implement encoders for your application needs.
A
digital optical encoder is a device that converts motion into a
sequence of digital pulses. By counting a single bit or by decoding a
set of bits, the pulses can be converted to relative or absolute
position measurements. Encoders have both linear and rotary
configurations, but the most common type is rotary. Rotary encoders
are manufactured in two basic forms: the absolute encoder where a
unique digital word corresponds to each rotational position of the
shaft, and the incremental encoder, which produces digital pulses as
the shaft rotates, allowing measurement of relative position of
shaft. Most rotary encoders are composed of a glass or plastic code
disk with a photographically deposited radial pattern organized in
tracks. As radial lines in each track interrupt the beam between a
photoemitter-detector pair, digital pulses are produced.
