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Absolute
Value Encoders
Absolute value encoders provide, directly after power-on,
the absolute position value without the machine moving. Single-turn
encoders sense the absolute position within a revolution,
while multi-turn encoders, aditionally code the number of
revolutions.
For absolute encoder, the following output transmission types
are available:
- SSI (Synchronuos Serial Interface)
- EnDat
- Profibus-DP
SSI and EnDat have advantages in time-critical applications.
In plant with large number of encoders, Profibus-DP is more
of an advantage due to reduced wiring expense. The encoders
with Profibus-DP are programmable.
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Absolute
Encoder Output Signals
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SSI
Output with 10-30VDC supply, Single Turn (4096
steps per revolution, 12 bits); Multi Turn (4096 steps
per revolution, 24 bits), with axial/radial flange socket |
| EnDat
Output with 5VDC supply, Single Turn (8192 steps
per revolution, 13bits), Multi Turn 8192 stes per revolution,
4092 revolutions, 25bits), with axial/radial flange socket. |
| Profibus-DP
Output with 10-30VDC supply, Single Turn (4096 steps per
revolution, 12 bits); Multi Turn (4096 steps per revolution,
24 bits), with axial/radial flange socket |
Single turn encoders resolve one rotation
(360 degrees mechanical) into a specific number of steps,
e.g. 8192. A unique code word is assigned to each position.
After 360 degrees the position values are repeated.
Multiturn encoders also record the number
of revolutions, in addition to the absolute position within
one revolution. To do this, further code discs which are coupled
through gear stages with the encoder shaft are scanned. When
evaluating 12 additional tracks, this means that 212 = 4096
revolutions can be included.
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