Siemens SINUMERIK 840C - Manual (Page 850)

09.95 12 Functional Descriptions
12.11.1 SIPOS absolute encoder up to SW 4
12.11.1.3 Synchronizing the absolute encoder with the machine
absolute system
After installation or after replacing the absolute encoder, the measuring system must be
synchronized with the machine system in the same way as with any incremental system. The
absolute encoder is set up with the following NC machine data.
• Axial machine data:
NC MD 240* reference point value
NC MD 396* absolute offset
• Machine data bits:
NC MD 1808* bit 0 = 1 axis with SIPOS absolute encoder
bit 2 = 0 absolute encoder same direction as the
machine system
1 absolute encoder opposite direction to
machine system
bit 3 = 0 absolute offset not valid
bit 3 = 1 absolute offset valid
Definition of terms:
Same direction: The absolute encoder value rises and falls with the machine
absolute value.
Opposite direction: The absolute encoder value rises as the machine absolute
value falls and vice versa.
Direct measuring system: The absolute encoder is a position measuring system (e.g.
linear scale) and is connected directly to the mechanical
section.
Indirect measuring system: The absolute encoder is used to measure position and speed
and is therefore connected to the motor.
There are two synchronization methods; these are explained below.
• Synchronization in ”Reference point approach” mode
Like any standard encoder, the SIPOS absolute encoder has A and B tracks and a zero
pulse.
Similar to the incremental system, the encoder is synchronized with the machine system
by combining the zero mark of the encoder with the reference point cam signal.
A distinction can be made between two cases by setting NC MD 1808* bit 0 = 1 ("Axis
with SIPOS absolute encoder") during reference approach.
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50 12–75
SINUMERIK 840C (IA)