All incremental encoders feature dual A/B output channels. Their code disks carry two offset grating tracks spaced 90° apart, generating A and B signals with a 1/4-period phase shift via photoelectric sensing. As the disk rotates, inner and outer gratings alternately block and transmit light; the timing gap creates the fixed phase offset between A and B pulses.

Rotation direction is identified by the A/B signal sequence. Pulse counts calculate displacement, while signal frequency derives rotational speed.

Many encoders add differential complementary channels /A and /B, also offset by 90°. Inverting and combining these complementary signals with A/B strengthens anti-interference performance. Most models integrate an extra Z index channel, with only one single grating slit on the disk. One Z pulse outputs per full rotation, serving as the zero reference for position calibration and counter reset.

Incremental encoders support arbitrary zero-point setup and unlimited multi-turn cumulative counting. Higher effective resolution is achievable via edge multiplication: triggering counts on both rising and falling edges of A/B pulses doubles the pulse number. A key limitation: all position data is lost after power cycling, requiring a homing procedure to relocate the Z zero reference.

Grating & PPR Definition

An incremental encoder’s code disk consists of alternating transparent and opaque grating stripes. The nominal line count (PPR, pulses per revolution) denotes complete A/B square-wave cycles per rotation, not total physical stripes.One full signal cycle corresponds to one transparent + one opaque stripe. Thus:Nominal PPR = Total physical grating stripes ÷ 2Example: A 1000 PPR encoder has 2000 physical stripes (1000 transparent + 1000 opaque) on its code disk.

Signal Generation Logic

As infrared transmit-receive sensors scan rotating gratings, one full A/B electrical pulse cycle is produced each time the sensor passes one transparent and one opaque stripe. For a 1000-PPR encoder, 1000 pairs of alternating stripes generate 1000 complete pulse cycles per revolution.

Ultra-Short Version (Product Page Brief Intro)

Incremental encoders output phase A and B signals with a fixed 90° phase shift from two offset grating tracks on the code disk. The A/B sequence judges rotation direction; pulse count measures displacement, and frequency reflects speed.Differential /A, /B signals can be added to boost signal stability, while the Z index channel outputs one pulse per rotation as a zero reference.Resolution can be doubled by counting both rising and falling edges of A/B signals. However, position data vanishes after power loss, requiring re-homing to find the zero point.

PPR (pulses per revolution) equals total physical alternating transparent/opaque gratings divided by two. A 1000-PPR encoder carries 2000 physical grating stripes and generates 1000 full pulse cycles per rotation.