Siemens Simatic S7-300 - Activating a Second Encoder; Using a Second Encoder

Expert Functions
5.4 Activating a Second Encoder
Connection of the SINAMICS S120 to the Technology CPU
146 Product Information, 09/2011, A5E00480378-04
5.4 Activating a Second Encoder
5.4.1 Using a Second Encoder
Introduction
A second encoder is required, for example, when the position detection does not supply
sufficient accuracy for the motor encoder or must be synchronized to external motions.
Second encoder as actual position value
For some mechanical constructions, the motor encoder cannot be used as an exact actual
position value on the system.
For such a construction, a gearbox with large play or slip is located between the motor and
the drive spindle. The motor encoder in such a case does not supply the actual position
value with sufficient accuracy.
Also the specification or the use of the slip in the parameterization of the axis in the
S7T Config project navigator for the Backlash Compensation parameter in the
"Technology\Axes\Axis_1\Mechanics" directory does not suffice to ensure an exact
position detection.
In such a case, a second encoder is mounted on the drive spindle and defined as
actual position value.
   
① Motor encoder
② Gearbox
③ Drive spindle
④ Motor encoder