What is the function of incremental encoder！

Incremental encoder

When the incremental encoder is moved, the encoder generates a stream of binary pulses that is proportional to the axis rotation speed (rotary encoder) or to the movement distance (linear encoder). With an optical encoder, a particular pattern of codewheel or linear code placed between the LED light source and the light sensor alternately turns on or off the light beam, thereby generating an analog signal; then additional circuitry, typically an on-board ASIC, Convert analog signal to square wave. Magnetic encoders can operate with a variety of mechanisms, but both rotate a magnetic field, thereby generating voltage pulses or resistance changes that can be converted to pulses.

The single-channel incremental encoder can only output single-pulse flow and therefore can only provide limited information. Depending on the resolution of the encoder, ie the number of pulses per revolution of the rotary encoder or the linear encoder movement (mm / inch), the external electronics can count pulses and calculate the velocity or relative to a reference coordinate Position), thereby determining the encoder position. Single-channel design provides an excellent solution for applications such as unidirectional conveyor systems.

The single-channel encoder is simple to operate, robust and economical, but it has one major drawback: the inability to determine the direction of motion. Determining the direction of motion requires more output from the encoder (usually a two-channel design with 90 ° phase difference for channel "A" and channel "B" independent output). The dual-channel encoder signal is sometimes referred to as a quadrature encoder because it has two rising edges and two falling edges. The direction of motion determines which channel first reaches a high level, which allows the processor to easily monitor the direction of motion (see Figure 1). The operator can increase the encoder resolution by triggering the pulse leading and trailing edges of one or both channels - up to a factor of 4.

Figure 1: The quadrature encoder produces two pulsed streams with a 90 ° phase difference so that the system can determine the direction of motion by monitoring which channel's phase is leading. Triggering the leading and trailing edges of the pulse increases encoder resolution - up to 4 times higher.

Quadrature encoders provide a robust solution for challenging and complex applications. In highly vibrating applications, single-channel encoders may misinterpret a pulsed flow generated by an axis jitter relative to a setpoint as a true displacement, while a quadrature encoder can recognize changes in direction and ignore pulsed flow or It is filtered out as noise.

The incremental encoder can also contain an additional channel, the index channel (or Z channel). This channel allows a rotary encoder or a linear encoder at a specific position to generate one pulse per turn (see Figure 2). The Z channel can determine a specific position at startup. In high-speed applications, using the Z-channel makes it easy to indicate a single turn and calculate the speed.

Incremental encoder generally only applies to simple applications, whether the control device is a counter, PLC or inverter, directly connected to the encoder and controller can be.

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