Technical Contrast

 

Quite simply: Optical encoders are vulnerable to three kinds of damage

 

       1.  The optical disk may shatter during 

            vibration or impact. 

 

       2.  The bearings fail due to stresses.

 

       3.  Oil, dirt, or water get inside the encoder

            due to seal failure.

 

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 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 errors when there is any type of contamination on the disk. Magnetic encoders do not make errors due to contamination.

 

Many optical encoders manufacturers attempt to reduce the causes of optical encoder failure and resulting sensor crashes by controlling the gap between the optical sensing element and the optical disk. This is expensive and requires the use of a separate bearing system integral to the encoder. Some will claim use of only shatterproof optical disks but these disks are still susceptible mechanical scratching. They will claim to use superior seals to keep contamination out and withstand a greater range of temperatures, but all these ‘band-aids’ only add cost.