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Quadrature encoders use alternating electrical pulses to very accurately measure the total rotation of whatever they are attached to, relative to when the encoder was turned on. The rotation can be easily converted to a linear distance if desired. When knowing absolute position is necessary, (such as in an elevator or arm) Quadrature encoders are still a good option, but must be paired with a method to “zero”. This usually takes the form of a Limit Switch.

This page describes the alternating electrical pulses. A quadrature encoder requires 4 wires: Power, Ground, Channel A, and Channel B.