This section provides an overview for incremental encoders as well as their applications and principles. Also, please take a look at the list of 11 incremental encoder manufacturers and their company rankings.
Table of Contents
An encoder is a type of electronic component that uses a sensor to detect the amount, direction, and angle of mechanical movement and output them as electrical signals.
Encoders are divided into incremental encoder and absolute encoders, depending on the detection method.
An incremental encoder is an encoder that can measure the amount of change in position/rotation after the power is turned on. An absolute encoder can detect the absolute position/rotation from the origin even after the power is turned off.
With an incremental encoder, the absolute position cannot be determined unless a homing operation is performed after the power is turned off. The difference between incremental encoder and absolute encoders is whether this homing is required or not.
Incremental encoders are used as position/speed detectors in a wide variety of machines, such as:
Incremental encoders are often used as a component of motors. The encoder detects the direction and angle of rotation of a rotating shaft and uses the information for position and speed control of the motor.
Incremental encoders are divided into optical encoders and magnetic encoders, depending on the electrical detection principle.
The position detection principle of incremental encoders is explained using an optical encoder as an example.
An optical encoder mainly consists of a light emitter, a light receiver, and a disc (scale).
The disc (scale) has a slit engraved on it. As the disc rotates, light emitted from the light emitter repeatedly passes through and is blocked by the slit, thereby generating light pulses on the photosensor. The number of pulses output corresponds to the amount of movement of the slit, and the amount of movement can be detected by the number of pulses counted.
The slit is engraved with three types of slits: phase-A, phase-B, and phase Z. The light receiving element detects these three types of pulses.
There are two types of encoders: linear encoders, which detect linear movement, and rotary encoders, which detect rotational angles. Figure 1 uses a rotary encoder as an example, but the principle itself is the same for a linear encoder.
In a rotary encoder, slits are engraved on a disk-shaped disk, whereas in a linear encoder, slits are engraved on a rectangular shaped scale like a ruler.
The rotational direction of FWD/REV can be detected by the order of the rising edges of the phase A and B pulses.
In FWD rotation, the rising edges of the phase A and B pulses are:
Phase A → Phase B → Phase A → Phase B → ...
Phase A→Phase B→Phase A→Phase B→...
In REV, the rising edges of the pulses of phases A and B are:
Phase B → Phase A → Phase B → Phase A → ...
Phase B -> Phase A -> Phase B -> Phase A -> ...
Since phases A and B are offset by 1/4 cycle, the direction of rotation can be determined by the order of the rising edges of the respective pulses.
The main specifications that can be used as an indicator when selecting an incremental encoder are as follows:
*Including some distributors, etc.
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