Quite simply, optical encoders are vulnerable to three kinds of damage:
Most styles of encoders come sealed from the factory. Over time, temperature cycling causes pressure changes and seals fail, which creates a path to the inside of the encoder. Often, the cause of the problem is simply moist air which enters the encoder and then condenses, rains or freezes inside the encoder.
Optical encoders need to see tiny lines on a disk accurately; they make optical errors when there is any type of contamination on the disk. Magnetic encoders do not make errors due to contamination.
Optical Avtron Encoders are designed to reduce the causes of optical encoder failure; they feature Wide-Gap technology to eliminate sensor crashes. Avtron Encoders use only shatterproof optical disks. They use superior seals to keep contamination out and withstand a greater range of temperatures than the competition.
Magnetic Avtron Encoders withstand dust, dirt, oil, water and heavy temperature cycling while providing the longest life and most reliable feedback. Magnetic technology enables the magnetoresistive sensor to “see” even when conditions inside the encoder look like a rainstorm of oil or water! Avtron Encoder models that are modular and magnetic even eliminate the bearings to increase reliability even further.
Generally, optical encoders can produce more pulses per revolution; for PPR above 2048, optical encoders may be the only choice. In the past, optical encoders were more accurate than some magnetic encoders, even at the same PPR. However, magnetic Avtron Encoder models are as accurate as most optical encoders.