Definition of encoder

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An encoder is a sensor used for motion control. It uses photoelectric, electromagnetic, capacitive or inductive induction principle to detect the mechanical position of the object and its changes, and converts this information into electrical signals after output, as the feedback of motion control, transmitted to a variety of motion control devices.

The purpose of encoder

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Encoders are widely used in machine tools, robots, motor feedback systems, and measurement and control equipment where precise determination of position and speed is required.

Classification of encoders

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Classification overview of encoders

According to the form of mechanical structure, encoders can be divided into rotary encoder and linear encoder.

The rotary encoder is the most widely used, mainly used to measure the Angle of mechanical equipment, speed or motor speed.

Linear encoders are mainly used to measure linear displacement, and can be divided into wire draw encoder and line encoder.

The wire encoder is a mechanical combination of a wire draw mechanism and a rotary encoder. The linear motion of the mechanical device is converted into a circular motion through the wire draw mechanism, so that the rotary encoder can be used to measure the linear displacement.

Linear encoder usually consists of a reader and a measuring ruler. By detecting the relative position between the reader and the measuring ruler, the mechanical position and its change can be calculated.

Encoders can be divided into incremental encoder and absolute encoder in terms of electrical output form.

The output of an incremental encoder is a periodically repeated signal, such as a square wave or a sine wave pulse. Therefore, it can be divided into square wave incremental encoder and sine and cosine wave incremental encoder.

Square wave incremental encoders are one of the most commonly used encoders. The length and speed are obtained by calculating the number and frequency of square wave pulses. Square wave incremental encoders have voltage outputs, such as TTL (also known as long wire drive, wire drive or RS422) and HTL (also known as push-pull or push-pull output), and switch outputs, such as NPN open collector output and PNP open collector output.

The output of the incremental encoder is generally 1VPP or 0.5VPP sine wave and cosine wave. By calculating the amplitude of sine and cosine wave, tiny angles can be accurately subdivided.

The output of the absolute value encoder is a specific digital code representing the actual position, and different coding rules correspond to different communication protocols, which are usually called communication interfaces.

Common communication interfaces of absolute value encoders are:

Analog quantity (e.g., 4-20mA current type output, 0-10V voltage type output, etc.)

Parallel ports (such as push-pull output and open collector output, with each core representing one digit of binary)

Serial port (such as RS485, RS232, RS422, etc.)

Industrial bus interfaces (e.g. SSI, PROFIBUS, DEVICENET, CANOPEN, etc.)

Industrial Ethernet interfaces (such as PROFINET, Ethernet IP, EtherCAT, Powerlink, etc.)

Absolute type encoder includes single-turn absolute absolute encoder and multi-turn absolute absolute encoder. The single-turn absolute value encoder can determine the Angle within one turn range, while the multi-turn absolute value encoder can determine the number of turns besides the Angle within one turn range.

According to the principle of detection, encoders can be divided into optical encoder, magnetic encoder, inductive encoder and capacitive encoder, etc.

The photoelectric encoder adopts the principle of optical detection, and the general detection accuracy is relatively high. However, it needs higher protection requirements when it is used outdoors and in harsh environment, and it is not suitable to be used in the condensation environment.

Magnetic encoder uses reluctance or Hall element to measure the Angle or displacement of magnetic material. Compared with the optical detection principle, the magnetoelectric detection principle has the characteristics of anti-vibration and anti-pollution, and can be applied to the fields that the traditional photoelectric encoder can not adapt to.

According to the mechanical installation mode, the encoder can be divided into solid shaft type and hollow shaft type, the hollow shaft type can be divided into blind hole type and through hole type. Encoders used for servo feedback are also commonly installed in the form of cone hole and cone shaft.

According to the applicable environment, encoders can also be divided into general industrial type, heavy-duty type and explosion-proof type.

According to the form of mechanical structure, encoders can be divided into rotary encoder and linear encoder.

The rotary encoder is the most widely used, mainly used to measure the Angle of mechanical equipment, speed or motor speed.

Linear encoders are mainly used to measure linear displacement, and can be divided into wire draw encoder and line encoder.

The wire encoder is a mechanical combination of a wire draw mechanism and a rotary encoder. The linear motion of the mechanical device is converted into a circular motion through the wire draw mechanism, so that the rotary encoder can be used to measure the linear displacement.

Linear encoder usually consists of a reader and a measuring ruler. By detecting the relative position between the reader and the measuring ruler, the mechanical position and its change can be calculated.

Encoders can be divided into incremental encoder and absolute encoder in terms of electrical output form.

The output of an incremental encoder is a periodically repeated signal, such as a square wave or a sine wave pulse. Therefore, it can be divided into square wave incremental encoder and sine and cosine wave incremental encoder.

Square wave incremental encoders are one of the most commonly used encoders. The length and speed are obtained by calculating the number and frequency of square wave pulses. Square wave incremental encoders have voltage outputs, such as TTL (also known as long wire drive, wire drive or RS422) and HTL (also known as push-pull or push-pull output), and switch outputs, such as NPN open collector output and PNP open collector output.

The output of the incremental encoder is generally 1VPP or 0.5VPP sine wave and cosine wave. By calculating the amplitude of sine and cosine wave, tiny angles can be accurately subdivided.

The output of the absolute value encoder is a specific digital code representing the actual position, and different coding rules correspond to different communication protocols, which are usually called communication interfaces.

Common communication interfaces of absolute value encoders are:

Analog quantity (e.g., 4-20mA current type output, 0-10V voltage type output, etc.)

Parallel ports (such as push-pull output and open collector output, with each core representing one digit of binary)

Serial port (such as RS485, RS232, RS422, etc.)

Industrial bus interfaces (e.g. SSI, PROFIBUS, DEVICENET, CANOPEN, etc.)

Industrial Ethernet interfaces (such as PROFINET, Ethernet IP, EtherCAT, Powerlink, etc.)

Absolute type encoder includes single-turn absolute absolute encoder and multi-turn absolute absolute encoder. The single-turn absolute value encoder can determine the Angle within one turn range, while the multi-turn absolute value encoder can determine the number of turns besides the Angle within one turn range.

According to the principle of detection, encoders can be divided into optical encoder, magnetic encoder, inductive encoder and capacitive encoder, etc.

The photoelectric encoder adopts the principle of optical detection, and the general detection accuracy is relatively high. However, it needs higher protection requirements when it is used outdoors and in harsh environment, and it is not suitable to be used in the condensation environment.

Magnetic encoder uses reluctance or Hall element to measure the Angle or displacement of magnetic material. Compared with the optical detection principle, the magnetoelectric detection principle has the characteristics of anti-vibration and anti-pollution, and can be applied to the fields that the traditional photoelectric encoder can not adapt to.

According to the mechanical installation mode, the encoder can be divided into solid shaft type and hollow shaft type, the hollow shaft type can be divided into blind hole type and through hole type. Encoders used for servo feedback are also commonly installed in the form of cone hole and cone shaft.

According to the applicable environment, encoders can also be divided into general industrial type, heavy-duty type and explosion-proof type.