How does an incremental optical encoder track position?

• A. Counting the dots which are sent as pulses
• B. Reading a single encoded signal
• C. Using GPS
• D. Measuring temperature

Answer: (A)

Incremental optical encoders track position by counting pulses produced as a patterned disk spins past a light sensor. The disk has many opaque and transparent regions (dots or slots); each time a region passes the detector, a pulse is generated. By tallying how many pulses have occurred since a known reference, you obtain the shaft’s relative movement and, with a known starting position, its current position. The higher the number of pulses per revolution, the finer the resolution. Many encoders also use a second channel in quadrature to determine direction, and some include an index pulse once per revolution to help re-establish absolute position after a power cycle. The important idea is: position is derived from counting pulses, not by reading a single encoded code, GPS, or temperature.