Encoder terminology explained: a simple glossary

If you're new to encoders, the terminology can sometimes seem confusing. From CPR and resolution to incremental and absolute, there are plenty of technical terms to get familiar with.

This simple glossary explains some of the most common encoder terms in plain English.

What is an encoder?

An encoder is a sensing device that converts mechanical movement into an electrical signal. Encoders are commonly used to measure position, speed, direction and distance in applications such as motors, robotics, automation and manufacturing equipment.

Absolute encoder

An absolute encoder provides a unique digital value for each position. This means the system can know the encoder's exact position, even after power has been switched off and back on.

Incremental encoder

An incremental encoder produces pulses as a shaft or component moves. These pulses can be counted to determine movement, speed and direction. Unlike an absolute encoder, an incremental encoder does not inherently retain its position when power is removed.

Resolution

Resolution describes the smallest movement or position change an encoder can detect. Higher resolution generally allows an encoder to provide more detailed position information.

CPR - counts per revolution

CPR (counts per revolution) refers to the number of position counts generated per revolution. Depending on the encoder and counting method used, CPR can differ from the stated PPR.

Quadrature

Quadrature is a method of using two encoder signals, usually called A and B, which are offset from one another. By comparing these signals, a control system can determine both the amount and direction of movement.

A, B and Z signals

The A, B and Z signals are the primary signals used by many incremental encoders to determine movement and direction.

The Z signal, sometimes called the index signal, provides one pulse per revolution. It can be used as a reference point.

Accuracy

Accuracy describes how closely the encoder's reported position corresponds to the actual position. Accuracy and resolution are related, but they are not the same thing as a high-resolution encoder isn't necessarily highly accurate.

Repeatability

Repeatability refers to an encoder's ability to return to the same position measurement consistently. Good repeatability is particularly important in precision automation and motion-control applications.

IP rating

An IP (Ingress Protection) rating indicates how well an encoder is protected against dust, water and other environmental conditions. The appropriate rating depends on where the encoder will be installed.

Shaft

The shaft is the rotating mechanical part of a rotary encoder. It connects the encoder to the equipment or mechanism whose movement is being measured.

Encoder feedback

Encoder feedback is the information sent from an encoder to a controller or drive. This feedback allows a system to monitor movement and make adjustments when required.

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