Industrial Encoders: Types, Applications, and Selection Criteria

Industrial machines need to know what their moving parts are actually doing. A motor may receive a command to turn at a certain speed or move to a certain position, but the control system still needs feedback to check the real movement.

An industrial encoder provides this feedback. It tracks the movement of a shaft or other machine part and sends a signal to a PLC, drive, or motion controller.

Depending on the encoder and system, this signal can be used to track:

Position — where a shaft or machine part is.
Speed — how fast it is moving.
Direction — which way it is moving or rotating.

Encoders are commonly found on electric motors, conveyors, CNC machines, robots, packaging equipment, and automated production lines.

But the same encoder won’t fit every machine. A conveyor used mainly for speed monitoring has different requirements from a CNC axis that needs precise position feedback. The control system matters too, as does the environment around the encoder.

So, encoder selection starts with the actual job: what movement needs to be measured, what feedback the controller needs, and where the encoder will be installed.

What Is an Industrial Encoder?

An industrial encoder is a device that turns mechanical movement into an electrical signal. The signal is sent to a PLC, drive, or motion controller, giving the control system information about what a machine is actually doing.

⁠Industrial encoders can measure two basic types of movement:

Rotary movement — rotation of a motor, shaft, wheel, or other rotating part.
Linear movement — movement along a straight path.

Depending on the encoder and how the signal is processed, the system can use this feedback to track:

Position — where the machine part is.
Speed — how fast it is moving.
Direction — which way it is moving or rotating.

For example, an encoder mounted on a motor shaft can tell the drive whether the motor is running at the required speed. On a positioning system, encoder feedback can tell the controller how far an axis has moved.

The encoder itself doesn’t control the movement. It measures what is happening and sends that information back to the control system.

Main Types of Industrial Encoders

Industrial encoders are generally divided into incremental and absolute types. Both measure movement, but they provide position information in different ways.

Incremental Encoders

An incremental encoder generates a series of electrical pulses as the shaft moves. The controller counts these pulses to calculate how far the shaft has moved.

Most incremental encoders use:

Channel A — generates pulses during rotation.
Channel B — produces a second pulse signal, shifted from Channel A. The controller compares the two signals to determine direction.
Channel Z or index — an optional signal that appears once per revolution and can be used as a reference point.

Because the controller counts movement from a starting point, incremental encoders are mainly used for relative position and speed feedback.

They are a common choice for:

motor speed feedback;
conveyors;
packaging machinery;
general industrial automation.

Absolute Encoders

An absolute encoder works differently. Each shaft position has its own unique value, so the controller can read the actual position directly rather than calculating it only by counting pulses from a starting point.

This means position information is available again after startup without first counting movement from zero.

There are two main designs:

Singleturn absolute encoders — identify the position within one complete shaft revolution.
Multiturn absolute encoders — track both the position within a revolution and the number of completed revolutions.

Absolute encoders commonly communicate with control systems through digital or industrial communication interfaces.

They are often used where knowing the actual machine position is important, including:

robotics;
CNC equipment;
positioning systems;
cranes and lifting equipment.

Optical vs Magnetic Encoder Technology

Industrial encoders can use different technologies to detect movement. Optical and magnetic sensing are two of the most common options, and each fits different working conditions.

Optical Encoders

Optical encoders use light and a coded or patterned disc to measure shaft movement. As the disc rotates, the optical system reads changes in the pattern and converts them into electrical signals.

Optical technology is often chosen when the application needs:

high resolution;
precise position feedback;
accurate speed measurement;
stable signals for motion control.

You’ll often find optical encoders in CNC machines, motors, positioning equipment, and other systems where small changes in movement need to be detected accurately.

Magnetic Encoders

Magnetic encoders measure movement using a magnetic field and magnetic sensing elements. They don’t rely on an optical disc and light source, which can make them a practical option for harsher working conditions.

Depending on the encoder design, they can handle environments with:

dust and dirt;
vibration;
shock;
other industrial contamination.

This makes magnetic encoders useful on heavy machinery, outdoor equipment, motors, and other applications where the encoder may face conditions that are difficult for some optical designs.

Neither technology is automatically better. Optical encoders are often selected when high resolution and precise feedback are the priority, while magnetic designs can be a better fit when environmental robustness matters more.

Factor	Optical	Magnetic
Resolution	Often very high	Model-dependent
Precision	High	Application-dependent
Contamination resistance	Depends on sealing	Generally strong
Harsh environments	Model-dependent	Often suitable
Typical use	Precision automation	Heavy-duty machinery

Industrial Encoder Applications

Encoders are used anywhere a machine needs feedback about position, speed, direction, or movement. The exact job depends on where the encoder is installed and what the controller needs to know.

Electric Motors

An encoder mounted on a motor can provide continuous feedback while the shaft is turning. The drive or controller can use this information for:

Speed feedback — checking actual motor speed.
Direction — detecting which way the shaft is rotating.
Closed-loop control — comparing actual movement with the command and making corrections when needed.

Conveyor Systems

On conveyors, encoders can be connected to a motor, drive shaft, or measuring wheel. Common tasks include:

monitoring belt speed;
measuring how far a product has traveled;
synchronizing two or more conveyors;
coordinating the conveyor with other machine operations.

CNC and Machine Tools

CNC equipment needs accurate feedback to keep machine movements under control. Encoders are commonly used for:

Axis positioning — tracking movement along a machine axis.
Spindle feedback — measuring spindle speed and position.
Motion control — providing feedback while the machine follows a programmed movement.

Robotics

Robots use encoders to keep track of their moving joints and motors. Encoder feedback can tell the controller:

where a joint is positioned;
how fast a motor is turning;
how far a joint has moved;
whether several axes are moving together as expected.

This feedback helps the robot coordinate multiple movements during the same operation.

Packaging and Manufacturing

Packaging and production machines often have several movements that need to happen at the right time. Encoders can be used for:

product positioning;
counting products or machine cycles;
synchronizing cutting with conveyor movement;
coordinating filling and packaging operations;
controlling automated machine sequences.

For example, an encoder can track a conveyor until a package reaches the required position. The controller can then trigger a cutting, filling, sealing, or labeling operation at the correct point.

Key Encoder Selection Criteria

Choosing an encoder starts with the movement you need to measure. Resolution matters, but so do speed, signal type, mounting, and the conditions around the encoder.

Resolution

Resolution tells you how much movement the encoder can detect.

Incremental encoders usually specify resolution in PPR (pulses per revolution).
Absolute encoders may specify resolution in bits or the number of positions per revolution.

More resolution gives the controller more detailed position information, but there is little benefit in choosing far more than the machine actually needs.

Speed

Check the encoder’s maximum operating RPM against the highest shaft speed in the application.

For incremental encoders, speed and PPR also determine the output frequency. A high-PPR encoder running at high RPM can generate pulses faster than the PLC or drive can process.

Output and Interface

The encoder signal must match the controller receiving it. Depending on the encoder, common options include:

TTL / RS-422;
HTL;
push-pull;
SSI;
BiSS;
CANopen;
Industrial Ethernet interfaces.

Before ordering an encoder, check both the electrical output and the controller input requirements.

Mechanical Design

The encoder also needs to physically fit the machine. Check:

solid shaft;
hollow shaft;
through-bore design;
shaft or bore diameter;
available installation space;
mounting method.

A mechanically incompatible encoder can create installation problems even if its electrical specifications are correct.

Environment

Finally, look at where the encoder will actually operate:

IP rating for protection against dust and water;
minimum and maximum temperature;
vibration and shock;
exposure to dust or moisture;
oils, chemicals, or other contaminants.

An encoder installed inside a clean machine enclosure may have very different requirements from one mounted on outdoor or heavy industrial equipment.

Resolution, Accuracy, and Repeatability

These three terms are related, but they describe different things:

Resolution — the smallest movement the encoder can distinguish.
Accuracy — how close the measured position is to the actual position.
Repeatability — how consistently the same position can be measured again.

A higher-resolution encoder gives the controller more detailed feedback, but it doesn’t automatically make the complete machine more accurate.

For example, the encoder may detect a very small shaft movement while the mechanical system still has play or positioning error. Final system accuracy can also be affected by:

gearbox or mechanical backlash;
coupling installation;
shaft alignment;
mechanical tolerances;
controller configuration.

So, resolution should be high enough for the required movement, but improving PPR or bit resolution alone cannot correct mechanical errors elsewhere in the system.

Incremental or Absolute: Which Should You Choose?

The choice between an incremental and absolute encoder depends mainly on what position information the machine needs.

Incremental	Absolute
Relative position	Absolute position
Pulse-based output	Position value
Often simpler	More advanced position feedback
May require referencing	Position available after startup
Strong choice for speed feedback	Strong choice for positioning

An incremental encoder works well when the main job is to measure speed, direction, or movement from a known starting point. The controller counts pulses as the shaft moves. If power is lost, the system may need to return to a reference position before normal operation continues.

An absolute encoder provides a specific value for each position. When the machine starts again after shutdown or power loss, the controller can read the encoder position without counting movement from zero.

In simple terms:

Choose incremental when speed and relative movement are the main requirements.
Choose absolute when the machine needs to know its position after startup or a power interruption.

The final choice also depends on the controller, required interface, resolution, machine design, and the type of motion being controlled.