What is the Difference between Absolute and Incremental Encoders?
Summary
TLDRThis video explores various types of encoders, focusing on linear and rotary encoders with absolute and incremental measurement capabilities. It explains how encoders like optical, magnetic, inductive, capacitive, and laser work to provide feedback on position, speed, and direction. The script delves into practical applications, such as CNC machines and robotics, and clarifies the differences between absolute and incremental encoders, highlighting their respective advantages in safety-critical and setup-intensive environments. Aimed at helping viewers make informed choices for their specific needs, the video also encourages learning PLC programming for career advancement.
Takeaways
- đ Encoders are essential components in various applications, and this video script provides an in-depth look at different types and their uses.
- đ There are two main sensing techniques for encoders: Linear and Rotary, with each category further divided into Absolute and Incremental measurement types.
- đ ïž Linear Encoders use a transducer to measure distance between two points, and can be used in applications like CNC milling machines for precise movement.
- đŻ Rotary Encoders, also known as Shaft Encoders, collect data based on the rotation of an object and can be used in applications ranging from computer input devices to robotics.
- đ Position Encoders are used to determine the mechanical position of an object, which can be either Absolute or Incremental, and are widely used in industrial applications for tooling and multi-axis positioning.
- đ Optical Encoders interpret data in pulses of light, determining position, direction, and velocity, and can be used in applications like printers, CNC milling machines, and robotics, with Absolute or Incremental capabilities.
- đ Absolute vs. Incremental: Absolute encoders, like Rotary Absolute, have a unique code pattern that allows for precise position detection, ideal for safety-critical applications. Incremental encoders, on the other hand, start at zero and count each revolution, useful for applications where the exact position is not crucial.
- đ ïž For Rotary Absolute encoders, the slotted disc on a shaft, in conjunction with a stationary pickup device, produces a unique code pattern for each position, ensuring accurate positioning.
- đ Incremental encoders begin their count at zero and record each revolution, making them suitable for applications where the exact position is not needed, but the relative change is.
- đ The script provides a practical example of using an incremental encoder to determine the travel count of an object on a conveyor, highlighting the difference between Absolute and Incremental measurements.
Q & A
What are the two main sensing techniques of encoders mentioned in the script?
-The two main sensing techniques of encoders mentioned are Linear and Rotary.
What is the purpose of a Linear Encoder in an application?
-A Linear Encoder uses a transducer to measure the distance between two points and can be used to determine the position of an object, such as in a CNC milling machine for precise movement measurements.
How does a Rotary Encoder differ from a Linear Encoder?
-A Rotary Encoder collects data and provides feedback based on the rotation of an object, converting an object's angular position or motion, whereas a Linear Encoder measures the distance between two points.
What are the two types of encoder measurement types discussed in the script?
-The two types of encoder measurement types discussed are Absolute and Incremental.
What is the difference between Absolute and Incremental Rotary Encoders?
-Absolute Rotary Encoders can measure angular positions, while Incremental Rotary Encoders can measure distance, speed, and position based on the number of signals per revolution.
In which applications are Rotary Encoders commonly used?
-Rotary Encoders are used in various applications such as computer input devices like mice and trackballs, as well as in robotics.
What is a Position Encoder and how is it used?
-A Position Encoder is used to determine the mechanical position of an object, providing an absolute position or detecting a change in position relative to the encoder, and is widely used in industrial applications for tooling and multi-axis positioning.
How do Optical Encoders interpret data to determine position, direction, and velocity?
-Optical Encoders interpret data in pulses of light, using a rotating disc with opaque segments that represent a particular pattern to determine the movement of an object for rotary or shaft applications, and exact position in linear functions.
What are the two types of Absolute Measurement Encoders mentioned in the script?
-The two types of Absolute Measurement Encoders mentioned are Single-turn and Multi-turn, with Single-turn used for short distances and Multi-turn for longer distances and more complex positioning.
How does an Incremental Encoder determine the position of an object?
-An Incremental Encoder creates an output signal each time the shaft rotates a measured amount, and the position is determined based on the count of signals from zero, without a definitive position unless a reference point is established.
What is the advantage of using an Absolute Encoder over an Incremental Encoder in safety-critical applications?
-Absolute Encoders are preferred in safety-critical applications because they provide a high degree of certainty regarding the exact position at all times, based on the unique pattern produced, without the need for a reference point after power disruptions.
Outlines
đ„ Introduction to Encoder Types and Techniques
This video starts by revisiting the concept of encoders and their implementation. It outlines the various types of encoders, such as linear and rotary, and highlights their primary sensing techniques. The script emphasizes the importance of understanding different encoder technologies like magnetic, optical, inductive, capacitive, and laser. It briefly touches on the fundamental configurations, such as linear and rotary encoders, explaining their operational principles and applications, such as CNC milling machines for linear encoders and computer input devices for rotary encoders.
đ Absolute vs Incremental Measurements Explained
The video delves into the differences between absolute and incremental measurements using rotary encoders as examples. Absolute encoders use a unique code pattern to determine the exact position, which is critical for safety and precision. In contrast, incremental encoders generate output signals based on the shaft's rotation, starting the count at zero upon power-up. The script provides an example with a conveyor system to illustrate how incremental encoders work and the necessity of a reference point for accurate positioning. The segment concludes by emphasizing the practical applications and the importance of choosing the right type of encoder based on specific requirements.
Mindmap
Keywords
đĄEncoder
đĄLinear Encoder
đĄRotary Encoder
đĄAbsolute Encoder
đĄIncremental Encoder
đĄPosition Encoder
đĄOptical Encoder
đĄMagnetic Encoder
đĄInductive Encoder
đĄCapacitive Encoder
đĄLaser Encoder
Highlights
Introduction to various types of encoders and their applications.
Explanation of the two main sensing techniques: Linear and Rotary encoders.
Differentiating between absolute and incremental encoder measurement types.
Overview of electromechanical technologies used in encoders, such as magnetic, optical, inductive, capacitive, and laser.
Linear Encoders use a transducer to measure distance between two points.
Linear Encoders can be used in CNC milling machines for precise movement measurements.
Rotary Encoders provide feedback based on the rotation of an object.
Applications of Rotary Encoders in computer input devices and robotics.
Position Encoders determine the mechanical position of an object, either absolute or incremental.
Optical Encoders interpret data in pulses of light to determine position, direction, and velocity.
Optical Encoders' use in printers, CNC milling machines, and robotics.
All encoders produce an electrical signal that can be translated to various measurements.
Explanation of Rotary Absolute Encoders using a slotted disc and stationary pickup device.
Absolute Encoders' preference in applications requiring a high degree of certainty and safety.
Incremental Encoders create an output signal each time the shaft rotates a measured amount.
Incremental Encoders require a reference point for positioning due to the lack of position safeguards.
Example of using an Incremental Encoder for counting revolutions of a conveyor belt.
Summary of encoder variations and guidance on choosing the appropriate type for specific applications.
Invitation to learn PLC programming and advance one's career at realpars.com.
Transcripts
Previously, we discussed what an Encoder is
and how it can be implemented in your application.
In this video, we are going to discuss the various types of encoders
and which encoder may be used for which function.
before we get started on today's video
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There are many types of encoders
but they basically fall into two main sensing techniques.
Those being: Linear and Rotary.
Within those categories, there are differing encoder measurement types
such as absolute and incremental.
There are also various electromechanical technologies
such as magnetic, optical, inductive, capacitive, and laser, to name a few.
There is a plethora of information regarding Encoders
and it may seem hard to wrap your head arounded.
Descriptions like rotary or linear, optical and magnetic, absolute and incremental.
We touch on a few basics to help you understand whatâs what and why.
Letâs first break these categories down a little
and explain a couple of the many configurations.
First, the Linear Encoder uses a transducer
to measure the distance between two points.
These encoders can use a rod or a cable
that is run between the encoder transducer
and the object that will be measured for movement.
As the object moves, the transducerâs data collected from the rod or cable,
creates an output signal that is linear to the object's movement.
As the distance is measured,
the Linear Encoder uses this information
to determine the position of the object.
An example of where a Linear Encoder may be used
is for a CNC milling machine
where precise movement measurements are required for accuracy in manufacturing.
Linear Encoders can be âAbsoluteâ or âIncrementalâ measurements.
We will touch on Absolute and Incremental measurements a little later.
A Rotary Encoder collects data
and provides feedback based on the rotation of an object
or in other words, a rotating device.
Rotary Encoders are sometimes called Shaft Encoders.
This encoder type can convert an objectâs angular position or motion
based on the rotation of the shaft,
depending on the measurement type used.
âAbsolute Rotary Encodersâ can measure âangularâ positions
while Incremental can measure things such as distance, speed, and position.
Rotary Encoders are employed in a wide variety of application areas
such as computer input devices like mice and trackballs as well as robotics.
Rotary or Shaft encoders, as previously stated,
may be âAbsoluteâ or âIncrementalâ.
The next encoder, which is a âPositionâ Encoder,
is used to determine the mechanical position of an object.
This mechanical position is an âabsoluteâ position.
They may also be used to determine a change in position between the encoder
and object as well.
The change in position in relation to the object and encoder
would be an incremental change.
Position Encoders are widely used in the industrial arena
for sensing the position of tooling and multi-axis positioning.
The Position Encoder can also be Absolute or Incremental.
âOpticalâ Encoders interpret data in pulses of light
which can then be used to determine such things as position,
direction, and velocity.
The shaft rotates a disc with opaque segments that represent a particular pattern.
These encoders can determine movement of an object
for ârotaryâ or âshaftâ applications
while determining exact position in âlinearâ functions.
Optical encoders are used in various applications such as printers,
CNC milling machines, and robotics.
Again, these encoders may be Absolute or Incremental.
After explaining the main groups, you may be seeing a pattern.
All the encoders basically do the same thing,
produce an electrical signal which can then be translated to position,
speed, angle, etc.
Now that we have broken down the main groups,
letâs discuss the difference between Absolute and Incremental measurements.
To discuss the difference between absolute and incremental measurements,
we will use the Rotary Encoder type as an example.
In a Rotary âAbsoluteâ measurement type encoder,
a slotted disc on a shaft is used in conjunction
with a stationary pickup device.
When the shaft rotates, a unique code pattern is produced.
This means that each position of the shaft has a pattern
and this pattern is used to determine the exact position.
If the power to the encoder was lost and the shaft was rotated,
when power is resumed, the encoder will record the absolute position
as demonstrated by the unique pattern transmitted by the disc
and received by the pickup.
This type of measurement is preferred in applications
requiring a great degree of certainty
such as when safety is a primary concern.
Because the encoder knows, at all times,
its definitive position based on the unique pattern produced.
Absolute measurement encoders can be single-turn or multi-turn.
âSingle-turnâ encoders are used for measurements of short distance
while âmulti-turnâ would be more suitable for longer distances
and more complex positioning requirements.
For incremental measure encoders,
the output signal is created each time that the shaft rotates a measured amount.
That output signal is then interpreted based on the number of signals per revolution.
The incremental encoder begins its count at zero when powered on.
Unlike the absolute encoder,
there are no safeguards regarding the position.
Because the incremental encoder begins its count at zero
in startup or power disruption,
it is necessary to determine a reference point for all tasks requiring positioning.
In the previous video,
when describing the use of an encoder for the purpose of counts,
that example is a good example of an incremental encoder.
Assume that the power has not been disrupted
and you have turned on the conveyor,
and placed the machine in setup mode.
As the encoder is turning the controller is receiving counts.
Letâs say the count range is 0 to 10000.
This is an incremental encoder so the absolute position is not known,
we just know that a full revolution of the shaft registers a count of 10000.
Weâll place the object on the conveyor and,
as soon as the entrance photo-eye sensor detects the object,
the current encoder count is captured.
Letâs say that number is 5232.
We will then capture the count with the object exiting
and being detected by the exit photo-eye.
Weâll say that the number is 6311.
So to determine the count of the full travel,
we will subtract 5232 from 6311
and determine that the object travel is 1079 counts.
By this example,
it is obvious that we do not know the absolute location of the object,
we just know that the travel count from the entrance to exit is 1079.
That doesnât tell us that the object is three inches from the exit,
just entering, etc.
we just know that the object will enter,
a count will be captured,
and the object will exit and again, the count captured.
In the event that we did not see the object exiting within the allowable travel count,
plus or minus a deadband, the machine will fault and the process will stop.
There are many, many encoder variations out there
and we could go on for hours about the varying types.
Hopefully, we have given you a basic understanding of whatâs out there
and when you may want to choose one particular type over the other.
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and take your career to the next level?
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