Encoder

An encoder is a device, circuit, transducer, software program, algorithm or person that converts information from one format or code to another, for the purposes of standardization, speed, secrecy, security, or saving space by shrinking size.


What is the basic definition of an encoder?
Answer: An encoder comes in two architectures. The first architecture is linear. The second architecture is rotary. Both types sense mechanical motion and translates the information (velocity, position, acceleration) into useful electrical data.
What isIncremental encoder?
An incremental encoder is a pulse generator that provides square–wave signals and a zero index.
The disc has 2 channels divided into “n” equal angular intervals; alternately opaque and clear. “n” is called resolution or number of counts.
Pulses counted by the processing electronics give the angular position of the rotor. For this purpose 2 squarewaves A and B are used with a third channel, Z, synchronous with signals A and B giving only one signal per revolution. It allows the user to initialize or reset the count.

Incremental encoder chart

what is Absolute encoder?
This concept has been developed to compensate for the performance limitations of incremental encoders :

• need for initialization

• must be re–zeroed after a power interruption: zero reset to obtain the mechanism angular position

• sensitivity to the interference

The absolute encoder supplies the shaft position as a binary code.
The output code is unique for each position. The resolution is equal to 2ⁿ(n= number of bit).
The shaft position information is given instantly when power is supplied.
There are two different types of absolute optical encoders :

• Single turn absolute optical encoder –> gives the absolute angular position over 360° rotation.
• Multiturn absolute encoder –> a system of additional shafts and discs which allows the number of revolutions to be counted.

The complete cycle is realized by « m » shaft rotations. The total resolution is equal to m x n (m=number of revolutions, n=number of counts per revolution).

Multiturn Absolute Encoder Principle

What is a channel? 
Answer: A channel is an electrical output signal from an encoder. Typical incremental encoders have either two or three channels. An example would be: A, A not, B, B not, and Z, Z not (also referred to I or I not.). 
What is the Index pulse (strobe, Z, and I.)? 
Answer: It is the absolute reference added to an incremental encoder. It is also known as home position. It signifies a full rotation of the encoder disk 
How can I reduce the effect of noise when using encoders? 
Answer: There are several ways to improve noise immunity. Be careful to separate motor and all power wires away from encoder wires. Always separate the channels from each other. All encoder wire should be shielded and carefully terminated. The pigtail that connects to the control unit using the encoder should be as short as possible. The leads will act as antennas for any stray RF in the vicinity. The addition of other noise suppression devices may be required in high noise environments. 

What equipment do I need to troubleshoot an encoder? 
Answer: A: An oscilloscope or specially designed encoder tester. A basic multimeter will do for basic diagnostics such as power supply and low speed pulse outputs. Any advanced pulse detection and diagnostics needs to be performed by a trained technician and an oscilloscope. 



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