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Technical Contrast

Why are Magnetic Encoders heavier duty than Optical Encoders?

 
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.
 

Why do contaminants (dirt, oil, water…) cause optical encoder failure, and not magnetic encoder failure?

 
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. 
 
P9112 Low Resolution Magnetic Encoder

P9112: 1.195 Inch body diameter, 1.0 inch bolt hole pattern, 26 AWG leads; Two Channel quadrature and pseudo quadrature outputs

FOR A COMPLETE LIST OF LOW RESOLUTION MAGNETIC ENCODERS - CLICK HERE

P9500 Medium Resolution Encoder

P9500: Total package size 1.80 inches wide, 1.25 inches long, .59 inces thick. Line driver differential ouputs

FOR A COMPLETE LIST OF MEDIUM RESOLUTION MAGNETIC ENCODERS - CLICK HERE

P9760: Total package size 6.5 inches long, 4.0 inches wide, 5.68 inch bolt hole pattern, integral connector or cabled connection interface

FOR A COMPLETE LIST OF HIGH RESOLUTION MAGNETIC ENCODERS - CLICK HERE

Select a Phoenix America Inc. Magnetic Encoder for severe environment conditions.

 

Phoenix America Magnetic Encoders withstand dust, dirt, oil, water, and heavy temperature cycling while providing the longest life and most reliable feedback. Magnetic technology enables the sensor to “see” even when conditions inside the encoder look like a rainstorm of oil or water! Phoenix America Inc. magnetic encoders even eliminate the bearings increasing reliability even further.

When is an optical encoder superior to a magnetic encoder? 

 
Rarely, some optical encoders can still produce more pulses per revolution than the Phoenix America Inc. Series 9700 but the requirement would need to climb to well over 10,000 PPR. In the past, optical encoders were more accurate than some magnetic encoders, even at the same PPR. However, Phoenix America Inc. continues to shatter the myth that magnetic encoders are less accurate as an optical encoders.
 

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