When a rotating shaft’s position, direction of motion or speed have to be measured, the rotary encoder is necessary. As you try to choose one, 2 things are here to choose from: the absolute encoder and the incremental encoder. We’ll help you to fill the difference in order to choose the best type of encoder for your project.
Understanding The Absolute Encoder
The absolute encoder offers a unique value for position or a data word at every single rotation point, which represents encoder absolute position. As you switch the design on, the absolute encoder lets you know the position of a rotating shaft measured.
This is done by using a capacitive, magnetic or optical sensor that reads a code from a disk rotating together with a shaft.
The absolute encoder manages to do everything without having to turn a shaft so position can be tracked even in the event there is a temporary power loss. If there are highly unique codes added to the disc of the encoder, the position reading ends up being highly precise.
Incremental Versus Absolute Encoders
The incremental encoder generates pulses while shaft rotates. The regular incremental encoder will generate 2 square waves with 90 degrees being out of phase. Such pulses have to be tracked or need to be counted with the use of electronics located on the outside of an encoder.
When Is The Absolute Encoder Preferred Over The Incremental Encoder?
An important thing to know is that due to the fact that absolute encoders maintain shaft position, you know the position as soon as power is delivered to the device. There is no need to wait for calibration or homing sequences to be complete. Position data is obtained and respected even if there is a power failure or the shaft was turned during the time when the encoder was not on.
It is often vital to know absolutely start up position since in some of the positions it is completely safe to keep rotating in a direction but it is not good in the other. Based on application, if you get this wrong, it can lead to bodily injury, equipment damage or a lot worse. Knowing exact rotating device position before parts move is oftentimes critical.
Just as important, the absolute encoder offers a true position in a true real-time setting. Many modern systems rely on digital technology, having connections to central communication buses. The fact that you are able to poll real-time position for the encoder when it is needed is a huge benefit, especially since latency is minimal. Keeping track of the position when using the incremental encoder, even if you go through a homing sequence, involves pulse tracking with the use of external circuitry. Besides the fact you need to use these external circuits, you also have to deal with position determination latency.
As you can see, the absolute encoder has many different situations in which the incremental encoder cannot be used. In fact, the absolute encoder is almost always preferred.