Core Mechanical Structure
The core of an incremental encoder consists of the code disk and the detection device:
Code Disk: Typically a thin, circular sheet (made of glass or metal) with evenly spaced, transparent/reflective slits (or conductive/insulating areas) along its edge. The angular difference between adjacent slits is called the "resolution" (e.g., 1024 lines per revolution, i.e., 1024 PPR).
Detection Device: Consists of a light source (e.g., an LED) and a photodetector (e.g., a phototransistor), with the code disk sandwiched between them. As the code disk rotates, the slits periodically block the light, causing the receiver to output a pulse signal.
Signal Generation Principle
When the code disk rotates, a pulse signal is generated through photoelectric induction. The specific process is as follows:
Fundamental Frequency Pulse (Phase A and Phase B): The code disk typically has two sets of independent slits (Phase A and Phase B), staggered by 1/4 cycle (90° electrical angle).
When the encoder rotates, phases A and B each output square wave pulses with a 90° phase difference (if phase A leads phase B by 90°, it's forward rotation; if phase B leads phase A by 90°, it's reverse rotation).
The number of pulses is proportional to the rotation angle: Angle = (Number of pulses / Total number of markings) × 360°.
Zero-position pulse (Z phase): An additional independent slit on the encoder outputs one pulse (Z phase) per revolution, used to determine the absolute zero position (e.g., motor homing calibration).
Signal Processing and Applications
Direction Determination: Forward/reverse rotation is distinguished by the phase relationship between phases A and B (e.g., phase B is high/low at the rising edge of phase A).
Speed Calculation: The number of pulses per unit time reflects the rotational speed: Rotational speed = (Number of pulses / Time) × (60 / Total number of markings) (Unit: r/min). Subdivision technology: Subdividing pulses through circuitry (e.g., 4x frequency multiplication) to improve resolution (e.g., a 1024-line encoder becomes equivalent to 4096 lines after 4x frequency multiplication).
