Encoder Explained: Incremental vs Absolute, Resolution and Signals

What the video shows

How an encoder works and how to choose one, in 7:22. Optical and magnetic encoders; on an incremental encoder, channels A and B are 90 degrees apart and give the direction, Z gives one index pulse per revolution, and counting every edge turns 2,500 lines into 10,000 counts per revolution. An incremental axis loses its position at power-off and must home; a Gray-code absolute encoder knows its position at power-up, and a multi-turn one counts revolutions with gears or a battery-backed counter. Resolution: 17 bit = 131,072, 20 bit = 1,048,576, 23 bit = 8,388,608 counts per revolution (364 / 2,913 / 23,302 per degree); at 1 rpm a 17-bit encoder moves about 2 counts per millisecond and a 23-bit one about 140, so low-speed motion is much smoother. Resolution is not accuracy. Signals: TTL/RS-422, HTL, SinCos, SSI, EnDat, Hiperface, BiSS and resolver. Motor encoder vs measuring wheel, field footage of an ONX rotary shear for 15 mm plate (the knife follows the line encoder, 10–80 m/min, ±0.5 mm), and five checks for choosing.