Siemens SIMATIC FM 453, Руководство пользователя

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9-64
FM 453 Servo Drive / Step Drive Positioning Module
C79000-G7076-C453-01
9.6.2 Absolute Encoders (SSI)
Absolute encoders (SSI) have several significant advantages over incremental
encoders:
S
Longer cable lengths
S
Reliable data capture by using a single-step GRAY code
S
No encoder synchronization needed.
You can use 13-bit single-turn encoders, or 25-bit multi-turn encoders with
the SSI protocol.
S
Absolute encoder (SSI) on linear axes
Make sure the value range of the encoder is at least equal to the traversing
distance of the axis.
S
Absolute encoder on rotary axes
Make sure that the absolute value range captured by the encoder corre-
sponds to a ratio of 2
x
or 2
–x
to one revolution of the rotary axis, and that
it encompasses at least one rotary axis revolution (see “Dependencies”
Section 5.3.1 and Figure 9-5).
Table 9-11 shows you how to adapt the selected encoder to the
FM 453.
Table 9-11 Function Parameters – Absolute Encoders (SSI)
MD Designation Value/Meaning Comments/Unit
10 Encoder type 3 = Absolute encoder (SSI 13
Bit)
4 = Absolute encoder (SSI 25
Bit)
13 = Absolute encoder (SSI 13
Bit)
14 = Absolute encoder (SSI 25
Bit)
GRAY Code
GRAY Code
Binary Code
Binary Code
11 Displacement per
encoder revolu-
tion (division pe-
riod) 1...1 000 000 000
see Section 5.3.1, Dependencies (MSR)
(integer portion)
12 Residual distance
per encoder revo-
lution 0...2
32
–1
see Section 5.3.1, Dependencies
(2
–32
MSR)
(fractional portion)
13 Increments per
encoder revolu-
tion (division pe-
riod) 2
1
...2
25
see Section 5.3.1, Dependencies
Entry according to
encoder rating plate
Overview
Absolute Encoders
(SSI)
Function
Parameters
Description of Functions