Absolute rotary encoders output a unique digital position code for every shaft angle, so the exact position is known immediately at power-up without any homing or reference travel, regardless of shaft movement during a power interruption. This is the key distinction from incremental encoders, which only report relative motion and lose their position reference when power is removed. Absolute encoders are available in single-turn designs, which report unique position within one revolution (typically 12 to 17-bit resolution), and multi-turn designs, which add a revolution counter to track position across thousands of turns using gear-based or battery/energy-harvesting counting methods. Internal sensing technology is either optical, offering the highest resolution and accuracy for precision applications, or magnetic, offering superior tolerance to dust, oil, moisture, and vibration for harsh-duty environments. Interface options are extensive, covering SSI, parallel binary, Gray code, and industrial fieldbus protocols including CANopen, Profibus, Profinet, EtherCAT, and DeviceNet, allowing direct integration with virtually any PLC or drive platform. Mechanical construction mirrors incremental designs, with solid shaft, hollow shaft, and blind hollow shaft mounting in aluminium or stainless steel housings sealed to IP65-IP67, plus heavy-duty variants for high shaft loads. Absolute encoders are specified wherever position must be known reliably after a power cycle or emergency stop - valve positioning, rotary index tables, robotic joints, crane and hoist drives, and any application where an unplanned homing cycle after power loss would be unsafe, slow, or unacceptable for cycle time.
