INDUSTRIAL ENCODERS

What is an Industrial Encoder?

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An industrial encoder is a sensor that converts mechanical movement into an electrical or digital signal that can be interpreted by a control system.

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Encoders are widely used in industrial automation, manufacturing, motion control and machinery to accurately measure:

• Position

• Speed

• Rotational speed (RPM)

• Distance or displacement

• Direction of movement

• Angle

• Number of rotations

• Acceleration

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The encoder sends this information to a control device such as a PLC, motion controller, counter, variable speed drive or servo drive. The control system can then use this feedback to monitor or control the movement of a machine.

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For example, an encoder fitted to a conveyor motor can tell a PLC how far the conveyor has moved, how fast it is travelling and in which direction it is moving. The PLC can use this information to stop a product at an exact position, synchronise multiple conveyors or adjust the motor speed.​

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This ability to provide accurate, real-time motion feedback makes encoders an important component in modern industrial automation systems.

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How Does an Industrial Encoder Work?

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An encoder detects mechanical movement and converts that movement into an electrical signal.

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The exact method depends on the type of encoder, but the basic process is:

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Mechanical movement → Encoder sensing element → Electrical/digital signal → PLC or controller → Machine control

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For a rotary encoder, the encoder is normally connected directly or indirectly to a rotating shaft. As the shaft turns, the encoder detects the rotation and generates electrical signals representing the movement.

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The machine's control system interprets these signals to determine information such as position, speed and direction.

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For example, if an encoder generates a known number of pulses for every revolution of a motor shaft, the controller can count those pulses to calculate how far the shaft has rotated. By measuring how quickly the pulses arrive, it can also calculate rotational speed.

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Some encoders provide significantly more sophisticated information, including an exact digital position value that can be available immediately when the machine is switched on.

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What Are the Main Types of Industrial Encoders?

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Industrial encoders can be classified in several different ways.

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The most important distinctions are:

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​Rotary vs linear encoders – describes the type of movement being measured.

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Incremental vs absolute encoders – describes how position information is generated and communicated.

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Optical vs magnetic encoders – describes the sensing technology used inside the encoder.

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Understanding these differences is important when selecting the correct encoder for an application.

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What Is a Rotary Encoder?

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A rotary encoder, sometimes called a shaft encoder, measures rotational or angular movement.

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It is typically connected to a motor, shaft, roller, gearbox or rotating machine component.

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Rotary encoders can be used to measure:

• Shaft position

• Angular position

• Rotational speed

• RPM

• Direction of rotation

• Number of revolutions

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They are commonly installed on motors, conveyors, packaging machinery, printing equipment, robotics, machine tools and automated production equipment.

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Rotary encoders are available in both **incremental and absolute** versions.

 

 

What Is a Linear Encoder?

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A linear encoder measures movement along a straight line rather than rotation.

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Linear encoders are commonly used when a control system needs to know the exact position, distance travelled or speed of a moving machine component.

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Typical applications include:

• CNC machinery

• Machine tools

• Cutting systems

• Gantry systems

• Automated positioning equipment

• Material handling

• Measuring equipment

• Linear axes and actuators

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Linear measurement can also be achieved using technologies such as wire-draw encoders, where a retractable cable converts linear movement into rotary movement that is measured by an encoder.

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What Is an Incremental Encoder?

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An incremental encoder generates a series of electrical pulses as the encoder moves.

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Each pulse represents a small amount of movement. By counting these pulses, a PLC, counter, drive or motion controller can calculate how far the machine has moved.

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The frequency of the pulses can be used to determine speed, while two channels – commonly called Channel A and Channel B – can be used to determine direction of rotation.

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Because the two signals are offset from each other, the controller can determine which direction the encoder is turning. This is commonly known as quadrature output.

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Many incremental encoders also provide a third signal called the Z channel, index pulse or reference pulse, which normally occurs once per revolution and can be used as a reference or homing position.

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Incremental encoders are particularly suitable for:

• Motor speed feedback

• Conveyor monitoring

• Length measurement

• Cut-to-length applications

• Positioning

• Machine sequencing

• Counting

• Synchronisation

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A key characteristic of an incremental encoder is that it normally provides relative rather than absolute position.

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If power is removed, the controller generally loses its accumulated position information. The machine may therefore need to return to a known reference or home position when restarted.

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What Is an Absolute Encoder?

 

An absolute encoder provides a unique position value for each measurable position of the encoder.

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Instead of simply generating pulses representing movement, the encoder communicates the actual position of the shaft or moving component.

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This means that the control system can determine the encoder's position without having to count movement from a starting point.

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One of the major advantages of an absolute encoder is that position information can be available again after a power interruption without requiring the machine to perform a conventional homing sequence, depending on the encoder and system configuration.

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Absolute encoders are therefore particularly valuable where knowing the machine's position is critical.

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Typical applications include:

• Robotics

• Packaging machinery

• Automated storage systems

• Cranes and lifting equipment

• Machine tools

• Rotary tables

• Pick-and-place systems

• Automated positioning systems

• Production machinery

• Servo systems

 

 

Single-Turn vs Multi-Turn Absolute Encoders

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Absolute rotary encoders can also be divided into single-turn and multi-turn encoders.

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A single-turn absolute encoder identifies the exact angular position of the shaft within one complete 360° revolution.

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A multi-turn absolute encoder can identify both the position within one revolution and the number of revolutions the shaft has completed.

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Multi-turn encoders are useful for applications where a machine may travel through many shaft rotations and the controller must still know its overall position.

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Incremental vs Absolute Encoder: What Is the Difference?

 

The fundamental difference is how the encoder reports position.

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An incremental encoder reports movement relative to a starting or reference position.

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An absolute encoder reports a unique position value.

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As a simple example, imagine a machine shaft is positioned at 127°.

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An absolute encoder can report that specific shaft position to the controller.

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An incremental encoder instead generates pulses as the shaft moves. The controller determines the position by counting those pulses from a known starting or reference position.

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Incremental encoders are commonly selected when:

• Speed measurement is important

• Relative position is sufficient

• The machine can easily perform a homing procedure

• Cost-effective motion feedback is required

• Pulse counting can be handled by the PLC or controller

 

Absolute encoders are commonly selected when:

• Exact position must be known

• Position needs to be recovered after power loss

• Homing is difficult, slow or undesirable

• Machine position is safety- or process-critical

• Complex positioning is required

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Optical vs Magnetic Encoders

 

Industrial encoders use several sensing technologies, with optical and magnetic sensing being two of the most common.

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Optical Encoders

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An optical encoder typically contains a light source, a coded or patterned disc and a light-sensitive detector.

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As the encoder shaft rotates, sections of the disc allow or interrupt the light reaching the sensor. The encoder electronics convert these changes into electrical signals representing movement or position.

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Optical encoders can provide very high resolution and accuracy, making them suitable for applications requiring precise motion feedback.

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Typical applications include:

• Precision machinery

• Servo systems

• Robotics

• Printing machinery

• Packaging machinery

• Machine tools

• High-accuracy positioning systems

 

 

Magnetic Encoders

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A magnetic encoder uses changes in a magnetic field to detect movement or position.

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Instead of relying on a light source and optical disc, magnetic encoders use magnetic sensing elements to detect the position of a rotating magnetic component.

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Magnetic encoders can be particularly suitable for harsh industrial environments where the encoder may be exposed to contaminants, vibration, dust or moisture.

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Typical applications include:

• Heavy industrial machinery

• Conveyors

• Mobile machinery

• Material handling equipment

• Outdoor equipment

• Harsh manufacturing environments

 

The best technology depends on the application. Optical encoders are often selected where very high resolution and precision are required, while magnetic encoders can offer advantages where environmental robustness is particularly important.

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Where Are Industrial Encoders Used?

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Industrial encoders are found throughout automated manufacturing and motion-control systems.

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Common encoder applications include:

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Conveyors and Material Handling

Encoders monitor conveyor speed, direction and distance travelled. They can also help synchronise multiple conveyors or position products accurately.

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Cut-to-Length Systems

An encoder fitted to a measuring wheel or roller measures how much material has passed through a machine so that products such as cable, sheet material, paper, steel or packaging can be cut to a specified length.

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Packaging Machinery

Encoders help synchronise conveyors, rollers, cutters, sealing equipment, filling equipment and labelling systems.

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Robotics

Encoders provide position and movement feedback for robotic joints, motors, wheels and linear axes.

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Motor Speed Feedback

An encoder mounted to a motor shaft allows a drive or controller to accurately monitor motor speed and direction.

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CNC and Machine Tools

Encoders provide precise position feedback for machine axes, spindles, rotary tables and positioning systems.

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Printing and Labelling

Encoder feedback synchronises printing or labelling with the movement of a product, web or conveyor.

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Filling and Bottling Equipment

Encoders help coordinate conveyors, filling heads, indexing systems and packaging processes.

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Automated Guided Vehicles and Mobile Robots

Encoders can measure wheel rotation, speed and distance travelled, contributing to vehicle positioning and motion control.

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Cranes, Hoists and Lifting Equipment

Encoders can measure drum rotation, position, travel distance and lifting movement.

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Sorting and Distribution Systems

Encoder feedback allows products to be tracked and positioned as they move through conveyors, sorting systems and automated warehouses.

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Why Are Encoders Important in Industrial Automation?

 

Modern automated machinery depends on accurate feedback.

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A motor may be instructed to rotate, but without feedback the control system may not know precisely how far it moved, how fast it moved or whether it reached the required position.

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An encoder provides this feedback.

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This creates a closed-loop control system where the controller can compare the commanded movement with the actual movement and make corrections where necessary.

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Encoders can therefore contribute to:

• Improved machine accuracy

• Better positioning

• Consistent product quality

• Accurate speed control

• Improved repeatability

• Machine synchronisation

• Reduced production errors

• Improved automation performance

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How Do I Choose the Correct Industrial Encoder?

 

Choosing the correct encoder involves more than deciding between incremental and absolute technology.

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Important specifications include:

• Rotary or linear measurement

• Incremental or absolute output

• Required resolution

• Maximum operating speed

• Shaft diameter and mounting arrangement

• Solid shaft, blind hollow shaft or through hollow shaft

• Supply voltage

• Output signal or communication protocol

• Cable or connector type

• Environmental conditions

• Operating temperature

• IP protection rating

• Shock and vibration requirements

• Required accuracy

• Electrical interface with the PLC, drive or controller

 

For incremental encoders, resolution is commonly specified as PPR (pulses per revolution) or in counts depending on the manufacturer and interface.

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Absolute encoders are generally specified according to the number of unique positions available per revolution, often expressed in bits or counts per revolution.

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Communication and electrical interfaces may include technologies such as:

• Push-pull

• Open collector

• Differential line driver

• SSI

• BiSS

• CANopen

• PROFIBUS

• PROFINET

• EtherNet/IP

• EtherCAT

 

Compatibility with the existing PLC, drive or motion controller should always be confirmed before selecting an encoder.

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Frequently Asked Questions About Industrial Encoders

 

What does an industrial encoder do?

An industrial encoder measures mechanical movement and converts it into an electrical or digital signal. This allows a PLC, drive or controller to determine parameters such as position, speed, direction, distance or rotation.

 

What is an encoder used for?

Encoders are used to provide motion and position feedback in industrial machinery. Common applications include conveyors, motors, robotics, packaging machines, CNC machinery, printing equipment, material handling systems and automated production lines.

 

What is the difference between an encoder and a sensor?

An encoder is a type of sensor specifically designed to measure motion or position. While industrial sensors may detect properties such as temperature, pressure, proximity or level, encoders primarily measure rotational or linear movement.

 

What is the difference between an incremental and absolute encoder?

An incremental encoder generates pulses representing changes in position. The controller counts these pulses to determine movement. An absolute encoder provides a unique value representing the actual position of the encoder.

 

Does an encoder measure speed?

Yes. A controller can calculate speed by measuring the frequency at which encoder pulses or position changes occur.

 

Can an encoder measure direction?

Yes. Incremental encoders commonly use two signals, known as A and B channels, which are electrically offset from each other. The controller uses the relationship between these signals to determine direction.

 

What does PPR mean on an encoder?

PPR means Pulses Per Revolution. It describes the number of pulses generated during one complete revolution of an incremental encoder. Higher PPR generally provides finer measurement resolution, although the controller's method of counting encoder signal edges must also be considered.

 

What is encoder resolution?

Encoder resolution describes the smallest change in position that the encoder can distinguish or report. Higher-resolution encoders provide more measurement points within a given movement or revolution.

 

What is a shaft encoder?

A shaft encoder is another common term for a rotary encoder. It measures the rotation or angular position of a shaft and converts this movement into an electrical signal.

 

Can an encoder connect to a PLC?

Yes. Industrial encoders are commonly connected to PLCs, high-speed counters, drives and motion controllers. The correct encoder output and electrical interface must be compatible with the receiving device.

 

What happens to an encoder when the power is switched off?

It depends on the encoder type. An incremental encoder normally requires the controller to establish its reference position again after power loss. An absolute encoder provides an absolute position value when the system restarts, subject to the specific encoder technology and system configuration.

 

Which is better: an optical or magnetic encoder?

Neither technology is universally better. Optical encoders are commonly selected for applications requiring very high resolution and precision. Magnetic encoders can be advantageous in demanding industrial environments where contamination, dust, vibration or moisture may be present.

 

Which encoder should I use?

The correct encoder depends on the movement being measured, required accuracy and resolution, operating speed, environmental conditions, mechanical mounting and the electrical interface required by the PLC or controller.

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For replacement encoders, the existing encoder's manufacturer, model number, PPR or resolution, supply voltage, output type, shaft dimensions, mounting arrangement and connector or cable configuration are useful starting points for identifying a suitable replacement.