Electric Motor Encoders: Position and Control
Encoders - Speed and Position Control
Encoders are electromagnetic devices providing an electrical feedback signal that is used to determine count speed, direction, and position control. Feedback from the encoder allows the system to determine if the object monitored is correctly positioned or moved.
What Do Encoders Detect?
Encoders detect rotation angles, rotational speed, and movement distance, translating these conditions into signals delivered to a motion control system.
Types of Encoders
Rotary Encoders
Rotary encoders are used to detect and provide feedback on rotating objects, such as the motor shaft. By converting the angular position of the rotating shaft into an output signal, the motion control system can determine the shaft’s speed or position.
Found in the following applications:
- Motor Shafts
- Packaging Equipment
- Robotic Technology
Linear Encoders
Linear encoders are used to report feedback on linear displacement. These encoders use a transducer to measure the distance and movement between two points.
Found in the following applications:
- Conveyor Systems
- Lift Controls
- Commercial Printing
Encoders Summarized
Encoder Types:
- Linear Encoders
- Rotary Encoders
Both Types Use These Measurement Methods:
- Absolute
- Incremental
Encoders Use These Technologies:
- Magnetic
- Optical
- Inductive
- Capacitive
- Laser
What is the Difference Between Absolute and Incremental Encoders?
For more information on your motor applications, contact one of our experts below
Measurement Methods
Absolute Encoders
Absolute encoders measure the position of the motor using a unique signal code pattern that directly reflects the position of the object. With this type of encoder, if there is a power loss, the encoder will resume recording the absolute position of the device when the power returns. Used in applications that require precision of the exact position of the object.
Incremental Encoder
Incremental encoders measure the relative movement of the object against a reference point, using a pulse counting technique. Unlike the absolute encoder, the incremental encoder has no way to record the exact location of an object if there is a power failure as it begins its pulse count from the original reference point each time the encoder is powered ON.
From this information, it is important to understand the difference between absolute and incremental encoders. An absolute encoder indicates the position, if it has changed, and the absolute position of the object. An incremental encoder does not indicate a specific position, only that the position has been changed.
Sensing Technologies Used in Encoders
Magnetic Encoders
Rely on a magnetic sensor to measure change in magnetic flux to determine movement and position of an object.
Optical Encoders
Most accurate EM sensing technology for encoders as it utilizes a light sensor and a patterned rotating disc to determine the movement and position of an object.
Capacitive Encoders
This technology is new and uses a high-frequency reference signal to detect a change in capacitance, which it then uses to measure movement and position of an object.
Inductive Encoders
Inductive encoders offer greater accuracy than magnetic encoders. This technology relies on sensors that react in the presence of magnets or electrically conductive metal in a target.
Laser Encoders
This encoder technology relies on a laser displacement sensor to translate the interference of two laser beams in order to determine the position or motion of an object.
Example of an Encoder in Action
One real-life example of an encoder in action can be seen in conveyor systems. The electric motor used to power a conveyor running 100ft/min has an encoder mounted to its shaft. The output from this encoder feeds into a controller telling it that everything is fine and that the motor is running at the correct speed.
If the load on the conveyor changes due to additional weight on the system, the controller will register a change in pulses from the encoder, causing the speed of the conveyor to slow down. In response, the controller will send a signal to the motor to speed up to compensate for this load change. Once the load has been returned to the expected load, the encoder will compensate for this change and adjust the speed of the motor accordingly.
Considerations When Selecting an Encoder
- What conditions need to be measured? (Speed, position)
- What type of motion you are working with? (Linear, rotational)
- What are the environmental conditions of the application?
- Does the sensing technology match the environment?
- What are the electrical requirements of the system?
- What are the mechanical requirements of the system? (Thru-bolt encoders, shaft encoders, etc.)
- How much accuracy is needed for the application and is there any potential for power loss? (incremental vs. absolute)
Talk To Our Sales Team
We're here to help. Our team of experts is ready to help energy-efficiently power your business.