What is an encoder?

1. What is an encoder?

Encoder” is classified as an electronic sensor that detects the amount and angle of movement of rotating and horizontally moving objects, and outputs electrical signals.

Since encoders excel in high-precision control, they are widely used in office equipment, machine tools, and industrial robots.

In recent years, the use of reflective encoders has increased in ultra-compact actuators, which are difficult to control, and they are also used in collaborative robots that require less space.

2. Types of encoders

2.1 Principle of electrical signal detection

Optical encoders: high accuracy and high magnetic fields
Magnetic encoders: simple and compact design, high durability

2.2 Types of electrical signal detection

Linear encoders: measuring linear shaft movement and outputs as position information
Rotary encoders: measuring rotational movement (angle) and outputs it as position information

2.3 Output methods

Incremental type” measuring the relative position

It starts from an arbitrary starting point, counts in a regular pattern, and outputs pulses according to the amount of movement.

Absolute type” measuring the absolute position

The absolute position from the origin is detected by the rotation angle of the encoder, and the data is output.

3. How does a rotary encoder work?


The encoder disk, which is used to measure the number of rotations of the motor, is mounted between the U-shaped parts shown in the illustration. This U-shaped component is called a “photo-interrupter“.

The photo-interrupter contains an infrared LED and a photo IC placed between the discs. Infrared light is irradiated and the number of times the LED light passes through the slit hole in the disc is measured.

This is how a rotary encode detects the angle of rotating objects.

4. What is an encoder scale?

Encoder scale” is one of the essential components of an encoder.

As shown in the figure below, an encoder generally consists of a light source, an encoder scale, and a photo-detector.

The encoder scale is responsible for transmitting or reflecting the light emitted by the light source. 

Therefore, it is no exaggeration to say that the processing accuracy of the encoder scale determines the measurement accuracy of the encoder.

Especially in recent years, with the increasing demand for high-resolution encoders, the need for high-precision scales is also increasing.

5. MELTEC’s encoder scale

We produce encoder scales, which are essential for motion controlling technology and are currently used in many applications as follows.


  • Industrial robotics
  • Positioning servos
  • Factory automation
  • Auto industry

Our company offers two types of encoder scales, “encoder code wheel” and “encoder strip“.

The former is a disc-shaped scale built into a rotary encoder device .

The latter is a linearly shaped scale that is incorporated into an encoder device detecting the position of a linear axis and outputs it as position information.

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5.1 Customized scale

We manufacture customized encoder scales, which meet customers’ requirements.

5.1.1 Advantages of customized scales
  • Customized encoder scales can be incorporated into encoders of sizes that are not compatible with standard encoder scales
  • Scales can be manufactured to match the encoder mounting hub size and mounting method
  • Possible to meet the requirement to realize high resolution encoders
  • Capable of manufacturing from a single prototype to mass production
5.1.2 Determining factor: Influenced specifications
  • Cost: Material and processing specifications
  • Reflectivity: Material and processing specifications
  • Application (encoder strip): Length and width of linear scale
  • Application (encoder code wheel): Inner diameter and outer shape of disc
  • Encoder accuracy: Resolution of the slit (LPI or CPR) and tolerance
  • Encoder type (incremental or absolute): Slit pattern

5.2 Product Features

  • Material: Metal, PET film, Resin
  • Applicable encoder type: Incremental/Absolute
  • Shape: Disc/Linear
  • Style: Transmission/Reflection
  • Combined processing: Assembly of reinforcement plate, double-sided tape, hub

5.2 Example products

5.2.1 Assembly with hub

5.2.2 Encoder disk unit

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