encoders and incremental encoders｜What are the differences between absolute encoders and incremental encoders?
What are the differences between absolute encoders and incremental encoders?
In the previous article, we explained the working principles of encoders and provided a detailed introduction to incremental encoders. In today's article, we will discuss another type of encoder: the absolute encoder.
As the name suggests, an absolute encoder is a type of encoder that can output absolute values. We know that the components of an encoder include a connecting shaft, code disk, light source, and output circuit, among others. The code disk of an absolute encoder differs significantly from that of a relative encoder, as shown in the diagram below:
On the left is the code disk of an absolute encoder, and on the right is the code disk of an incremental encoder. It can be observed that the grating on the code disk of the incremental encoder is evenly distributed, while the code disk of the absolute encoder is divided into many unequal bands. The following diagram may provide a clearer illustration:
The output of an Absolute Encoder is a set of binary-coded values. Its code disk is divided into many concentric channels, with each channel referred to as a "bit channel." Each bit channel has a separate output circuit to represent a binary bit. For example, in the diagram above, the outermost bit channel represents Bit 0, followed by Bit 1, Bit 2, and Bit 3 as we move inward. The more bit channels there are, the larger the measurable range. The waveform diagram below illustrates the output circuit waveform when the code disk rotates:
Absolute encoders can be categorized into single-turn and multi-turn types. Single-turn encoders measure the absolute position within one revolution, suitable for angular displacement measurement. Multi-turn encoders can measure the number of revolutions, depending on the encoder's design, and are commonly used for length measurement and determining precise positions within a certain length.
Some key differences between absolute encoders and incremental encoders include:
Incremental encoders output pulse signals, while absolute encoders output a set of binary values.
Incremental encoders do not have power-off retention, while absolute encoders can retain data after a power outage.
The number of revolutions for incremental encoders is unlimited, whereas absolute encoders cannot exceed their revolution range.
Incremental encoders are generally more cost-effective.
Remember that the main distinction between absolute encoders and incremental encoders lies in the design of the code disk. Additionally, many industrial encoders currently support bus interface outputs (such as Profinet). These encoders with integrated bus interfaces can be accessed directly through bus communication, providing convenient integration.
This concludes the introduction to knowledge about absolute encoders.