6.13 Increment-coded reference marks
In the case of encoders with increment-coded reference marks, multiple reference
marks are distributed evenly across the entire travel distance. The absolute position
information, relative to a specific zero point of the measurement system, is
determined by counting the individual measuring increments between two reference
marks. The absolute position of the scale defined by the reference mark is assigned
to precisely one measuring increment. Before an absolute reference can be created
or the last selected reference point found, the reference mark must be passed over.
In the worst-case scenario this requires a rotation of up to 360°. To determine the
reference position over the shortest possible distance, encoders with increment-
coded reference marks are supported (e.g. HEIDENHAIN ROD 280C).
The reference mark track contains multiple reference marks with defined increment
differences. The tracking electronics determines the absolute reference when two
adjacent reference marks are passed over after just a few degrees of rotation.
Number of
pulses (P
542)
Number of ref-
erence marks
Basic increment G Nom-
inal Increment A (P 610)
Basic increment G
Nominal increment
B (P 611)
18 x 1000
lines
18 basic marks
+ 18 coded
marks = Σ 36
Reference measure A =
1000 lines
corresponding to 20°
Reference
measure B =
1001 lines
Table 6.38: Example of a rotary system on encoder channel Ch1
MOOG
ID No.: CB40859-001 Date: 11/2020
MSD Servo Drive - Device Help
105
6 Encoder
Image 6.13: Schematic view of circular graduations with increment-coded reference
marks
①
Increment-coded reference measure B, large increment (1001 lines):
P 611[0] -
ENC_CH1_NominalIncrementB
②
Increment-coded reference measure A, small increment (1000 lines):
P 610[0] -
ENC_CH1_NominalIncrementA
③
Zero point: Parameter
P 542[0] - ENC_CH1_Lines
is used to enter the number
of lines (e.g. 18 x 1000). A sector increment difference of +1, +2, +3 and +4 is
supported. One mechanical revolution is precisely one whole multiple of the
basic increment A.
Legend for Schematic view of circular graduations with increment-coded reference
marks
