Axis, Drive And Encoder - Siemens simatic et 200s Operating Instructions Manual

1PosUniversal/Digital
7.6 Functions of the 1PosU
7.6.2

Axis, Drive and Encoder

Evaluation of the Encoder Signals
The 1PosU evaluates the signals supplied by the position encoder differently depending on
the position encoder type:
SSI encoder:
The 1PosU evaluates the encoder value supplied by the SSI encoder directly in increments
and forms the actual value in increments (actual value = encoder value).
The actual value lies in the encoder range from 0-(number of rotations * number of
increments)-1. The 1PosU generates an overrun or underrun of the actual value at the limits
of the operating range.
Incremental encoder:
The 1PosU evaluates the pulses supplied by the position encoder four times and adds them
up direction-specifically to form the actual value. You must take the quadruple evaluation into
account when you make settings for paths in the parameters and in the control and feedback
interfaces:
1 pulse of the incremental encoder corresponds to 4 increments of the 1PosU.
The current value is in the operating range 0 - 16 777 215 increments. The 1PosU generates
an overrun or underrun of the actual value at the limits of the operating range.
Incremental encoder at dosing operation:
The 1PosU only evaluates the rising edges of the "Track A" signal and adds them up to form
the actual value.
The current value is in the operating range 0 - 16 777 215 increments. The 1PosU creates
an overflow of the actual value at the upper limit of the operating range.
Reversal of the direction of rotation
You can use the parameter for the reversal of the direction of rotation to adapt the direction
of rotation of the encoder to that of the drive and the axis.
In dosing operation reversal of the direction of rotation is not possible.
324
Operating Instructions, 05/2007, A5E00124871-04
ET 200S Positioning