What are the two main categories of optical encoders?

• A. Analog and Digital
• B. Incremental and Absolute
• C. Rotary and Linear
• D. Single-ended and Differential

Answer: (B)

Optical encoders are categorized by how they represent position. Incremental encoders produce pulses as the shaft moves, and you must count those pulses (and reference a home position) to determine your location. They’re simple and high-resolution, but don’t know the absolute position on their own after power-up unless you re-reach a zero reference. Absolute encoders, on the other hand, provide a unique position code for each angle or travel amount, so the exact position is known immediately—even after power loss. This makes them more robust in returning to the previous state without re-homing, though they can be more complex and costly.

Other terms describe different aspects that aren’t the same as how position is encoded: Analog vs Digital refers to signal form rather than encoding method; Rotary vs Linear describes the motion path being measured rather than the encoding approach; Single-ended vs Differential relates to output signaling style rather than how position is represented.