Incremental encoder
Sine encoder
Smart Feedback Device (SFD)
Mechanical shock and vibration resistance
Fair to good
Temperature rating
Typically same as motor windings: up to 170°
80 to 115°C
Typically same as motor windings: up to 170 °C
–20 to 115°C
Dependent on resolver to digital (R/D) converter, typically 12 to 16 bits (4,096 – 65,536 counts for single speed type)
500 to 20,000 lines (2,000 – 80,000 counts) or more per revolution (4,000 lines is typical minimum for velocity control)
500k to 2 million counts depending on amount of interpolation of the fundamental number of lines of resolution
> 16 million based on 224 built-in interpolation of integral single speed resolver
10 to 20 arc-min
3 to 5 arc-min; can be much less Stegmann Endat encoders are 45 arc-sec
20 to 60 arc-sec
9 to 16 arc-min
12,000 rpm or more
Typically 7,000 rpm maximum
12,000 rpm or more however can be limited by an input frequency limitation of the amplifier
12,000 rpm or more
Analog requiring R/D converter or interpolation in software
Digital output
Analog — requires converter or interpolation in software
Dynamic response
Good, signal conversion results in some phase delay
Good to excellent, related to resolution of device
Excellent due to high resolution
Excellent – update every 51.2 sec
Commutation method
Direct based on absolute feedback of resolver (motor poles must be evenly divisible by resolver poles)
Requires additional Hall-effect devices or commutation tracks to initialize motion until absolute position can be determined
Direct based on absolute feedback nature of sine encoder
Direct based on the absolute feedback nature of the device
Distance from controller
Up to 75 m (typical)
Up to 30 m (typical)
Up to 40 m (typical)
Up to 75 m or more (typical)
Cable conductors
Three pair
Seven pair
Five pair
Two pair – two for power, two for RS-485
Low to moderate
Moderate to high
Low to moderate
This table provides a brief operating summary of the four most 1common feedback devices used with servomotors.

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