quadrature-encoder-course/lessons/01-reading-encoder-signals/01-meet-the-quadrature-encoder/meet-the-quadrature-encoder.md

title	summary	chapter	order	tags	estimated_minutes
Meet the Quadrature Encoder	Learn what the A and B channels are and why their phase offset lets you count motion.	Reading Encoder Signals	1	encoders motors feedback	8

Meet the Quadrature Encoder

A quadrature encoder gives you two square-wave signals, usually called A and B.

Those signals toggle as the shaft turns. The important detail is that they do not toggle at the same time. One channel leads the other by a quarter of a cycle, which is where the name quadrature comes from.

That phase offset gives you two useful facts:

1. You can count edges to measure motion.
2. You can compare which signal leads to determine direction.

What you should observe

• Slow rotation produces clean transitions you can inspect with a logic analyzer.
• Reversing the shaft swaps which channel leads.
• More pulses per revolution means finer position measurement.

Checkpoint

Capture both channels while rotating the shaft by hand and confirm that one channel leads the other.