Speed and position feedback encoder, to track accurate digital for motors

there are several types of motors, that they maybe need encoder to track speed and position to get an accurate data.

for example, it contains AC motor encoder, servo motor encoder,stepper motor encoder.

1. AC Motor Encoder

AC induction motor is a popular choice for general automation machine control systems for their economical and rugged characteristic.

encoders is widely used for precise speed control systems which are using AC motors, 

and usually needs to have higher protection grade(IP), shock and vibration requirements.

2.Servo Motor Encoder (sometimes called permanent magnet motor encoder)

 Servo motor provides closed loop feedback control systems to some devices,

 which requires higher precision and accuracy, and do not need higher protection grade as AC induction motors. 

encoders work for servo motors can be modular, incremental or absolute type and bearingless encoder types.

3.Stepper Motor Encoder

 Stepper motor is less  costly, high precision, and is typically applicated on open-loop system.

In open-loop system using stepper motors where speed control is asked, an incremental motor encoder is often used for stepper motor.