The output of a rotary encoder is dependent on what is required by the application. There are two output forms which are incremental and absolute. Incremental output forms take form of square-wave outputs. For an application requiring an incremental encoder, the output signal is either zero or the supply voltage. The output of an incremental encoder is always a square-wave due to the switching of high (input voltage value) and low (zero) signal value. Absolute encoders operate in the same manner as incremental encoders, but have different output methods. The resolution of an absolute encoder is described in bits. The output of absolute encoders is relative to its position in a form of a digital word. Instead of a continuous flow of pulses as seen by incremental encoders, absolute encoders output a unique word for each position in form of bits. Equivalent to 1,024 pulses per revolution, an absolute encoder is described to have 10 bits (210 = 1024).

The resolution of incremental encoders is frequently described in terms of cycles per revolution (CPR). Cycles per revolution are the number of output pulses per complete revolution of the encoder disk. For example, an encoder with a resolution of 1,000 means that there are 1,000 pulses generated per complete revolution of the encoder.

When selecting the proper encoder for any application, the user must also take into account noise and cable length. Longer cable lengths are more susceptible to noise. It is crucial to use proper cable lengths to ensure the system functions correctly. It is recommended to use shielded, twisted-pair cables with preferably low capacitance value. The rating for capacitance value is normally in capacitance per foot. The importance of this rating is for well defined square-wave pulse outputs from the encoder rather than “jagged” or “saw-toothed” like pulses due to the interference of noise.

The index channel is an optional output channel which provides a once per revolution output pulse. This pulse allows for the user to keep track of position and establishes a reference point. This output channel is extremely valuable for incremental encoders when an interruption of power occurs. In instances with a power failure, the last sustained index channel can be used as a reference marker for a restarting point. Therefore, when such an occurrence takes place, an index channel can prove to be quite valuable in applications utilizing incremental encoders. Absolute encoders do not have an issue with losing track of position in power loss situations, because every position is assigned a unique bit configuration.

Cover and base options are considerations for specific application requirements. Enclosed cover options help protect the encoder from dust particles. Base options play a significant role in large vibration environments. Such mounting options are transfer adhesives which stick directly on the back of the encoder to the mounting surface, molded ears for direct mounting. Anaheim Automation also offers various base options for mounting purposes.