Absolute Encoder

An absolute encoder is a high-precision sensor that directly outputs the current position. The core characteristic of an absolute encoder is that each position has a unique encoded value (usually binary or Gray code). It accurately retains position information regardless of whether the device is powered on, without needing to return to zero or recalibrate. This differs from incremental encoders, which rely on pulse counting and lose position information when power is lost.

Absolute encoders typically operate based on optical, magnetic, or inductive sensing technologies. They detect rotational or linear displacement through internal optical or magnetic gratings, generating corresponding digital signal outputs. These output signals can be transmitted to the control system via analog signals, pulse signals, or digital interfaces to achieve precise position, speed, and direction feedback.

Based on structure and function, absolute encoders can be divided into single-turn and multi-turn types:

Single-turn absolute encoder: A single-turn absolute encoder records the position within one rotational range, with each angle having a unique encoded value. Even when powered off, a single-turn absolute encoder retains the current angle information without needing to return to zero. Single-turn encoders have a relatively simple structure, low cost, high accuracy, and fast response speed, and are widely used in equipment requiring precise single-turn positioning. However, single-turn absolute encoders are limited by their inability to record the total number of rotations, making them unsuitable for multi-turn cumulative positioning scenarios.

Multi-turn absolute encoder: Multi-turn absolute encoders, on the other hand, can not only record the position within a single turn but also accumulate the number of rotations, achieving precise positioning over a multi-turn range. Multi-turn absolute encoders typically sense the total number of rotations through internal gears or electronic counters, and retain the total position and current angle even after power loss. Multi-turn encoders are suitable for applications requiring multi-turn cumulative positioning, offering high precision and reliability, but their structure is relatively complex and their cost is also higher.