A rotary encoder that generates pulses proportional to shaft rotation, used for speed measurement and relative position tracking.
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The elevator incremental encoder outputs two quadrature (90°-phase-shifted) square wave channels (A and B) and an index channel (Z) per revolution. Pulse resolution is typically 1024 or 4096 pulses per revolution (PPR). The VFD counts encoder pulses to calculate motor speed for vector control. The controller counts cumulative pulses from a known reference point (index or floor sensor) to track car position. Unlike absolute encoders, incremental types lose position on power loss, requiring re-homing by running to a floor sensor at startup. Signal integrity requirements are stringent: shielded cable, differential line drivers (RS-422), and separation from power cables are mandatory. Common failure modes include bearing wear, disc damage, connector corrosion, and cable breakage. EN 81-20 requires speed monitoring for overspeed protection functions to use reliable feedback such as encoder signals.
