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Definition, use and classification of rotary encoders

source:HEYYEN Electronics (Shanghai) Co., Ltd.time:2019-08-28views:Loading...

  Rotary encoder definition

  A rotary encoder is a sensor for motion control. It uses photoelectric, electromagnetic and other working principles to convert the mechanical speed, angle and position changes of the detected object into electrical signals, and outputs this information as feedback of motion control to various motion control devices.

  Rotary encoder use

  Rotary encoders are widely used in applications where precise position and speed are required, such as mechanical equipment, machine tools, motor feedback systems, and measurement and control equipment.

  Encoder classification

  Overview of the classification of rotary encoders

  Figure: Overview of the classification of rotary encoders

  Rotary encoders are the most widely used and are used to measure the angle, speed or speed of a machine.

  According to the type of the code wheel, the rotary encoder can be classified into an incremental encoder and an absolute encoder.

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

  Square wave incremental encoders are one of the most commonly used encoders, which derive length or velocity information by counting the number or frequency of square wave pulses. The square wave incremental encoder has various output circuit types such as TTL (also called long line drive, line drive or RS422), HTL (also called push-pull output or push-pull output), NPN open collector, etc. depending on the output circuit.

  The output of the sine-cosine incremental encoder is typically 1Vpp sine and cosine. By subdividing the voltage volts of the sine and cosine, the encoder signal can be multiplied to achieve higher output resolution.

  Absolute encoders output absolute position information such as angle and position through different communication protocols.

  Common communication interfaces for absolute encoders are:

  Analog (eg, 4-20mA current output and 0-10V voltage output, etc.)

  Parallel ports (such as push-pull output and open collector output, each core represents a binary one digit)

  Serial port (such as RS485, SSI, BISS, ENdata, etc.)

  Industrial bus interface (such as Profibus-DP, DeviceNet, CANOpen, etc.)

  Industrial Ethernet interfaces, etc. (eg PROFINET, Ethernet IP, EtherCAT, POWERLINK, etc.)

  The absolute encoder includes a single-turn absolute encoder and a Muliti-turn absolute encoder. The single-turn absolute encoder can determine the angle within a circle, while the multi-turn absolute encoder can determine the number of turns in addition to the angle within a circle.

  According to the detection working principle, the encoder can be divided into an optical encoder and a magnetic encoder.

  The photoelectric encoder adopts the optical detection principle, and the general detection precision is relatively high, but it requires high protection requirements when used outdoors and in harsh environments, and is not suitable for use in a condensation environment.

  Magnetic encoders use magnetoresistance or Hall elements to measure the angular and positional changes of magnetic materials. Compared with the optical detection principle, the magnetoelectric detection principle has the characteristics of anti-vibration and anti-pollution, and can be applied to more severe environments.

  According to the mechanical installation method, the encoder can be divided into a shaft type and a sleeve type, and the sleeve type can be divided into a blind hole type and a through hole type. Encoders for servo feedback are also commonly used in mounting configurations such as taper and taper.

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

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