Encoders are used to monitor various parameters, such as current, speed, and the relative position of the rotor in real-time during the operation of a motor. This information is used to determine the status of the motor and any connected devices, allowing for real-time control of their operation. By using encoders as front-end measurement components, the measurement system is greatly simplified, while also providing precise, reliable, and powerful functionality.
Encoders are rotary sensors that convert physical quantities, such as position or displacement, into a series of digital pulses. These pulses are collected and processed by the control system, which then sends commands to adjust or change the operating state of the device. Encoders can also be used to measure the position or displacement of linear motion components when combined with gears or lead screws.
Encoders are precision measurement devices that combine mechanical and electronic components to encode or convert signals or data for communication, transmission, and storage. Encoders are classified based on different characteristics, as follows:
Encoders work by using a central shaft with a circular optical encoder disc that has annular light and dark lines. These lines are read by optical emitters and receivers to obtain four sinusoidal wave signals that are combined into A, B, C, and D signals. Each sinusoidal wave is 90 degrees out of phase with respect to one full cycle of 360 degrees. The C and D signals are reversed and added to the A and B signals to enhance the stability of the signal. Each rotation also outputs one Z pulse to represent the zero position reference.
Because the A and B phases are 90 degrees out of phase, the direction of rotation of the encoder can be determined by comparing whether the A phase is ahead or the B phase is ahead. The zero position pulse can be used to obtain the zero position reference of the encoder.
Encoder discs can be made of glass, metal, or plastic. Glass discs have very thin lines deposited on the surface, providing good thermal stability and high precision. Metal discs have lines that are directly etched, providing good durability but lower precision due to the thickness of the metal. Plastic discs are economical, but their precision, thermal stability, and lifespan are lower than those of glass discs.
Encoder resolution refers to the number of light or dark lines provided by the encoder per 360-degree rotation, also known as the resolution or number of lines. Typical encoder resolutions range from 5 to 10,000 lines per rotation.
Encoders play a crucial role in elevators, machine tools, material processing, electric motor feedback systems, and measurement and control devices. Encoders use optical grating and infrared light sources to convert optical signals into TTL (HTL) electrical signals. By analyzing the frequency and number of high levels of the TTL signal, the rotational angle and position of the motor can be directly reflected.
Because both the angle and position can be accurately measured, encoders and inverters can be combined to form a closed-loop control system, making the control more precise. This is why elevators and machine tools can operate with such precision.
In summary, encoders can be classified into incremental and absolute types based on their structure. Both types convert other signals, such as optical signals, into electrical signals that can be analyzed and controlled. In everyday life, devices such as elevators and machine tools rely on precise control of motors through electrical signal feedback closed-loop control, and encoders combined with inverters make precise control possible.