The Theory of Incremental Encoder！

Incremental shaft encoders also known as Incremental Rotary Shaft Encoders are ideal for monitoring sensing a rotating shaft, or even linear position sensing when used in conjunction with ball screws etc, rollers. When integrated into a control system, they provide speed, position, acceleration & direction feedback data to the system. Incremental encoders produce a series of pulses directly proportional to movement of its shaft. Incremental encoder pulses usually consist of two square-wave signals known as A channel & B channel (also known as 1 channel & 2 channel).

An incremental encoder is also provided with a digital Marker Pulse (also known as a Reference pulse, Z channel, or 0 channel). This is a single pulse per revolution of the shaft. The pulse can be used by the control system counter as a reset, reference, checking pulses, revolution counter as well as many other functions. The Marker channel can usually be supplied in various forms such as, un-gated (of no fixed width), gated with A (only high when A is high), gated with B (only high when B is high), or gated with A & B (only high when A & B are high).

When it is required to determine the angular position of rotating shafts then a rotary encoder or optical encoder is used. They usually take the form of a miniature electric motor in appearance, and sometimes get mistaken for stepper motors.

The optical encoder drive shaft is directly coupled to a rotating spindle via a flexible coupling. An electric signal is derived from the unit in a system of digital pulses. This pulse train is produced by a combination of a calibrated disc and light emmitting diode.
The disc, which is attatched to the encoder shaft, rotates, cutting a beam of light produced by the diode. The number of pulses obtained is dependant on the number of graduations set out on the disc. There is a very wide range of encoders available and it is important to select for particular applications. Pulse lines can be as low as 1 pulse/rev to as high as 20000 pulses/rev and can be powered at 5v or 11-30v.  Greenbank stock the Italsensor Encoder TK561 with 1024ppr and 11/30V supply.

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