Term description

Photoelectric encoder

A sensor that converts the mechanical geometric displacement on the output shaft into a pulse or digital signal through photoelectric conversion

Photoelectric angle encoder

Photoelectric encoders with an angle measurement and an accuracy level is more than 20 ″ (inclusive).

Photoelectric rotary encoder

Photoelectric rotary encoder is used for rotary motion measurement. The absolute encoder accuracy level is below 20 ″ level, and the incremental encoder accuracy level is below 0.05T level.

Incremental photoelectric encoder

A photoelectric encoder that obtains position values by calculating the number of incremental pulse signals from a reference point.

Absolute photoelectric encoder

At any position within the full range, photoelectric encoders with a single-valued function relationship.

Single-turn absolute photoelectric encoder

The measuring range is single-turn absolute photoelectric encoder.

Multiple-turn absolute photoelectric encoder

The measuring range is multi-turn absolute photoelectric encoder.

Incremental and absolute hybrid photoelectric encoder

Photoelectric encoder that simultaneously outputs incremental signals and absolute signals.

Integrated photoelectric encoder

It has a rotating datum, and it is at least a photoelectric encoder composed of three basic parts: a shaft system, a circular grating disk, and a reading head.

Solid shaft photoelectric encoder

The photoelectric encoder whose output shaft is a solid shaft.

Hollow shaft photoelectric encoder

The photoelectric encoder whose output shaft is a hollow shaft.

Semi-hollow shaft photoelectric encoder

The photoelectric encoder whose output shaft is a blind hole.

Split photoelectric encoder

There is no rotating reference, and the photoelectric encoder is composed of at least two basic parts : the circular grating disk and the reading head.

Basic parameter terms


The logarithm of the graduation line of the incremental grating encoder.

Pulse number per rotation

The number of pulses output per revolution of the incremental photoelectric encoder.

Bit number per rotation

The number of bits of the binary code output by the absolute encoder.

Maximum rotary speed per minute

The maximum number of rotations per minute allowed by the photoelectric encoder.

Maximum response speed per minute

The number of mechanical revolutions that reach the electrical limit response frequency of the photoelectric encoder.

Index signal

Pulse signal for marking the absolute position of incremental photoelectric encoder.

Note: The incremental photoelectric encoder can have one or more reference marks.

Output model

The type of hardware interface circuit for the photoelectric encoder signal output.

Open collector output

A circuit that uses the transistor emitter as the common terminal and the floating collector as the output terminal.

Note: Open collector output is generally divided into NPN open collector and PNP open collector output.

Voltage output

On the basis of the open collector output, a pull-up resistor is installed between the power supply and the collector, and the collector is used as the output terminal.


Push-pull output


The output circuit has two transistors, NPN and PNP.

Note: According to [H], [L] of the output signal, the two output transistors alternately perform [ON] and [OFF] actions, which can be slightly farther than the open collector output circuit transmission distance, and can also be input device with the open collector output (NPN, PNP) connection

Line driver output

Adopt differential output, suitable for high-speed, long-distance data transmission output mode.


Parallel interface output


Each cable of the absolute encoder represents one bit, the high or low level represents 1 or 0, and all bits are output in parallel.


Synchronization serial output


Both communication parties have a common clock reference, and can use the clock reference to accurately send and receive data.

Note: Usually this clock reference is the synchronous clock line or the same clock source.


Asynchronous serial output


The two parties of communication do not have a common clock reference, and usually need to have a preamble for rate synchronization output every time they send and receive data

Main parts terms


Usually the material is glass, metal, or film .

Serve as a reference for measuring the scale of an optical encoder.

Indicative grating

A series of engraved lines engraved on a carrier such as glass, metal, or film as an incremental photoelectric encoder to indicate the measurement reference.


The part that drives the measurement reference to rotate and is used to partially connect with the user.

Main body

Components for supporting other devices of encoder


Used to protect the internal parts of the encoder from external pollution.


It is composed of a main shaft, a main body, and a bearing to obtain a rotating reference.


It is used to flexibly connect the encoder output shaft with user's end.

Connection plate

A component used to flexibly connect the encoder body with the fixed end of the object to be measured.

Reading head

A photoelectric conversion device of encoder composed of a light emitting system and a receiving system.

Technical Term

Angular resolution

The ability of the encoder to resolve the two smallest angle values.

Note: The angular resolution of the absolute encoder is expressed by the ratio of the full-angle angle value and the output bits of the absolute encoder; the angular resolution of the incremental encoder is expressed by the full-angle angle value and output the number of pulses of the incremental encoder.

Output channel

The output signal number of incremental photoelectric encoder.

Output phase difference

When the encoder is working, the electrical angle difference between the rising and falling edges of the two signals of the A phase and the B phase.

Direction of rotation

From the direction of the shaft end of the photoelectric encoder, the same rotation direction as the clockwise rotation, and the opposite rotation direction is the counterclockwise direction

Error of measurement

The difference between the measured value of the photoelectric encoder and the theoretical value.

Error of the uniformity of pulses

The difference between the measured pulse period To and the theoretical value T of the photoelectric encoder.

Allowed angle rotary acceleration

The maximum angular velocity increase per time allowed by encoder.

Maximum response frequency

The highest frequency reached by the photoelectric encoder.



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