Omron Cam Positioner Cam Positioner

Solid Shaft / Hollow Shaft Absolute Encoders

Application
An absolute encoder provides the ability to remember the exact position following any power interruption. There is also no need for synchronisation. This is one of the reasons why absolute encoders are used where a safety standard is required (i.e. robotics industry). Typical applications are for speed or position control circuits. The features for these encoders are:

+ A unique signal for each angular position
No need for initialisation (zero reference)
Immediately after power up or after an interruption of power the position is maintained
No need for a counter to process the signal

Construction
The electrical signal of the absolute encoder is directly related to the angle of the shaft. The mechanical angular position is sensed by non contact optical elements, therefore without wear. The output of an infrared diode is transmitted through a transparent code disc and a diaphragm. The light/dark pattern is converted to an electrical signal by an array of photo diodes. The same code occurs only once per revolution. This encoder is defined as a single turn encoder.

Output circuit

Types of Code
Any electronic code is made out of a combination of bits. Each bit is characterised by a Low (0) or a High (1) signal. The combination of a series of bits is called a binary word. Several binary words make a code.

Single Step Code - Only one bit on the parallel output changes state at any given time. There is no possibility of any concurrent state changes. Single step code is very versatile and can maintain accuracy even allowing for slight misalignments of the disc and scanning device
Gray Code - This is a single step code, most absolute encoders use this code
Multiple Step Codes - Natural binary code: This type of code is similar to the decimal system, except that there are only 1 and 0. Each bit, depending on its position in the binary word, has a definite value. 2⁰ to 2ⁿ assigned