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What are the two classification methods for encoders?!

Changchun Rongde Optics Co.,Ltd.   Release time:2018-11-23   Browse:761

The encoder is a precision measuring device that is tightly coupled mechanically and electronically. It converts a mechanical geometric displacement into an electrical signal by photoelectric or electromagnetic principles. This electronic signal usually needs to be connected to the control system, and the control system can calculate the measured data for the next step.

According to the working principle, the encoder can be divided into two types: incremental and absolute. The incremental encoder converts the displacement into a periodic electrical signal, which is then converted into a counting pulse, and the number of pulses is used to represent the magnitude of the displacement. Each position of the absolute encoder corresponds to a certain digital code, so its indication is only related to the start and end positions of the measurement, regardless of the intermediate process of the measurement.

According to the detection working principle, it can be divided into photoelectric encoder and electromagnetic encoder.

Magnetic encoder features: strong, anti-vibration, dust, dirty, wet; low cost;

Features of photoelectric encoder: high resolution, higher precision, through-hole bushing.

Incremental encoder:

Incremental encoders usually have three output ports, which are A-phase, B-phase, and Z-phase outputs. The A-phase and B-phase are delayed by 1/4 cycle pulse output, and the forward-reverse can be distinguished according to the delay relationship. The 2 and 4 octaves can be performed by taking the rising and falling edges of the A and B phases; the Z phase is a single lap pulse, that is, one pulse per revolution.

The grating of the incremental measurement consists of periodic grids. The position information is obtained by counting the number of increments (measurement steps) from a certain point. Since the position value must be determined with an absolute reference point, the circular encoder disk also has a reference point track.

Absolute encoder:

Absolute encoders correspond to a circle, and each reference angle emits a binary value unique to the angle. The external ring device can record and measure multiple positions.

The position value is immediately available when the encoder is energized and ready for subsequent signal processing electronics to read. The reference point zeroing operation is performed without moving the axis. The absolute position information comes from a circular raster disk, which consists of a series of absolute codes. A separate incremental track signal generates a position value by subdivision, and also generates an incremental signal for selection.

The absolute position value information of the single-turn encoder is repeated once per revolution.

Multi-turn encoders can also distinguish position values ​​per revolution.

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