Incremental Encoder (Quadrature)
Converts shaft rotation into a pulse train — two channels (A and B) in quadrature give position and direction.
Use this when…
- Measuring conveyor belt speed or position
- Providing axis position feedback to a servo drive or PLC motion module
- Counting print head rotations on a labelling machine
Pick-and-place robot
Encoders on each servo axis stream position data to the motion controller, enabling precise multi-axis path following.
Palletiser conveyor
A line encoder on the main conveyor provides belt speed to the palletiser PLC, synchronising product pickup with belt motion.
An incremental encoder generates a pulse each time the shaft rotates by a fixed angle. The number of pulses per revolution (PPR) — also called resolution or line count — determines how finely position can be measured. A 1000 PPR encoder generates 1000 complete A-B cycles per shaft revolution.
Quadrature encoders have two output channels, A and B, shifted 90 degrees apart in phase. By examining which channel leads the other, the PLC can determine direction of rotation: if A leads B, the shaft is rotating forward; if B leads A, it is rotating backward. With quadrature decoding (counting both edges of A and B), the effective resolution is multiplied by four.
The Z channel (index pulse) produces one pulse per revolution at a fixed reference position. This allows the controller to re-home the axis after power-up without returning to a physical limit switch.
PLC high-speed counter (HSC) modules process encoder signals directly in hardware, decoding the quadrature and accumulating the count at speeds up to several MHz — far faster than the PLC scan cycle could handle in software.
Common output types are HTL (push-pull, 10-30 V, suitable for long cable runs) and TTL (differential RS-422, fast, noise-immune). Always match the encoder output type to the HSC module's input specification.
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