Measuring angles with rotary encoders

Mounting variants

In rotary encoders with integral bearing and stator coupling, the graduated disk of the encoder is connected directly to the shaft to be measured. The scanning unit is guided on the shaft via ball bearings, supported by the stator coupling. During angular acceleration of the shaft, the stator coupling must absorb only that torque resulting from friction in the bearing, thereby minimizing both static and dynamic measuring error. Moreover, the coupling mounted on the stator compensates axial motion of the measured shaft. Other benefits of the stator coupling are:

• Simple mounting
• Short overall length 
• High natural frequency of coupling 
• Hollow-through shaft possible 
  
  Rotary encoders with integral bearing that are conceived for separate shaft coupling are designed with a solid shaft. The recommended coupling to the measured shaft compensates radial and axial tolerances. Angle encoders for separate shaft couplings permit higher shaft speeds.
  
  Rotary encoders without integral bearing operate without friction. The two components - the scanning head and the scale disk, drum, or tape - are adjusted to each other during assembly. The benefits are:  

• Large diameter of hollow shaft  
• For high shaft speeds 
• No additional starting torque