Page 27 - Keubler Motion Sensors
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Basics
Encoders Absolute encoders
Versions Singleturn encoders Multiturn encoders
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Depending on the number of divisions they generate Up to 17 bit unique angular positions per revolution
unique positions per revolution. After one complete are provided. In addition the number of revolutions is
revolution the process re-commences at the start detected. Up to 4096 (12 bit) unique revolutions can Product overview
position. be made available on the output.
They are suitable for angular measurement over a Multiturn encoders are suitable for angular Basics
maximum of one turn of the shaft (=360°), for exam- measurement over more than one turn of a shaft, for
ple in robotics, with cam controllers and in other example with longer traverse paths, such as high
controlled rotary motion. rack storage areas, cranes or machine tools.
Code types Binary code
The Binary code can be processed very easily by (LSB, LSB+1...) is not exactly synchronized. Due to
computer systems. When using optical read-out, this, without any correction of the code, the position
errors may occur, because the change from one bit information could be wrong.
to another on the different concentric tracks
bit 1 (LSB)
bit 2
bit 3
bit 4 (MSB)
Significance 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Gray code
The Gray Code is a single-step code, which guar- This leads to reliable scanning of the code and
antees that from one position to the next only 1 bit consequently of the positions.
changes.
Symmetrically capped Gray code (Gray-Excess):
If a particular section of the complete Gray Code is This permits even-numbered divisions, such as 360,
extracted, this results in the so-called Gray Excess 720, 1000, and 1440.
Code
bit 1 (LSB)
bit 2
bit 3
bit 4 (MSB)
Significance 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
bit 1 (LSB)
bit 2
bit 3
bit 4 (MSB)
Significance 0 1 2 3 4 5 6 7 8 9
Reversion of the Gray code
The code values increase when the shaft is turning The Gray code is reversible, i.e. if the most signifi-
clockwise. cant bit (MSB) is inverted, the code values decrease
when the shaft is turning clockwise.
© Fritz Kübler GmbH, subject to errors and changes. 02/2015 www.kuebler.com 25
