Text version of the page

General/Basics

Rotary Measuring Technology – Absolute Encoders

Versions:Singleturn encoders: Multiturn encoders: Depending on the number of divisions theygenerate up to 16384 (14 Bit) unique posi- tions per turn. This corresponds to anangular resolution of 0.022° (= 1.3’). Afterone revolution the process re-starts.Singleturn encoders can be used in appli-cations where revolution is sufficient, e.g. measurement of angles, robotic. They are available with up to 8192 (13 Bit) definite angular positions per revolution and in addition 4096 (12 Bit) definite revolutions. This corresponds to 33.5 million definitepositions.Multiturn encoders can be used for posi-tioning applications e.g. automatic storage, retired systems, lift elevators, cranes, machine tool, etc.

Code types:

Binary Code: The Binary Code can be processed veryeasily by computer systems. When usingoptical read-out, errors may occur, because the change from one bit to another on thedifferent concentric tracks (LSB, LSB+1...) isnot exactly synchronized. Due to this, with-out any correction of the code, the position information could be wrong. Bit 1 (LSB) Bit 2Bit 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. Thisindicates, that from one position to the next only 1 bit is changed. The reliability of thecode detection is increased, which leads toa high position-reliability. The Gray Code isused to optically read out the position for all absolute encoders Symmetrically cut Gray Code(Gray-Excess): The extraction of a defined part of the Gray Code leads to the gray-excess code. Thiscode enables the generation of non binarybased divisions, e.g. 360, 720, 1000, 1440. Bit 1 (LSB) Bit 2 Bit 3Bit 4 (MSB)
Significance 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15Bit 1 (LSB) Bit 2 Bit 3Bit 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 isturning clockwise. If the most significant bit(MSB) is inverted, the code values decreasewhen the shaft is turning clockwise.
1/2008 www.kuebler.com 25