Sensor Technology and Application Basics

Catalogs > Sensors Catalog > Sensor Technology and Application Basics > Encoders

Encoders

Encoders Incremental Versus Absolute Encoders Mechanical Installation and Accessories Applications Accessories
Incremental Versus Absolute Encoders

Incremental Encoders

The graphic below shows the code disk for an incremental encoder. Incremental encoders generate a series of pulses as they move and provide relative values. Incremental encoders provide speed and distance feedback. They are typically simple and inexpensive. Incremental encoders provide relative position information.

Click to enlarge - 845_Incremental Code Disk


Incremental Outputs

Click to enlarge - 845_Incremental Outputs


Absolute Encoders

An absolute encoder has a unique digital output for each shaft position that provides true, or absolute, position regardless of power interruptions. The code disk for an absolute encoder uses an absolute track with straight binary, binary coded decimal, or gray code to provide absolute position data. Upon a loss of power, the encoder will provide the correct absolute position when power is restored. Absolute encoders are used for packaging machines, robotics, lead/ball screw, and pick and place applications, to name a few. Gray code provides the most reliable high speed positioning at the lowest cost.

Absolute Code Disk with Grey Code

  Binary Coded Decimal Natural Binary Grey Code
Click to enlarge - 845_Absolute Code Disk w Grey Code 0 0000 0 0000 0 0000
0 0001 0 0001 0 0001
0 0010 0 0010 0 0011
0 0011 0 0011 0 0010
0 0100 0 0100 0 0110
0 0101 0 0101 0 0111
0 0110 0 0110 0 0101
0 0111 0 0111 0 0100
0 1000 0 1000 0 1100
0 1001 1 1001 1 1101
1 0000 0 1010 0 1111
1 0001 0 1011 0 1110
1 0010 0 1100 0 1010
1 0011 0 1101 0 1011
1 0100 0 1110 0 1001
1 0101 0 1111 0 1000
  

Latch, Direction, and Reset Features


Single-turn versus Multi-turn

In a single turn encoder, the output codes are repeated for every revolution of the encoder shaft. There is no mechanism to indicate whether the encoder had made one revolution or several revolutions. All that is output is the relative position. In a multi turn absolute encoder, the output is unique for each shaft position through every rotation up to x number of revolutions.

Single turn absolute encoders are used when full range of positioning in the application is not greater than one full revolution (360 degrees) of the encoder shaft – an example is rotary table positioning.

Multi turn absolute encoders are used when a full range of positioning in the application requires multiple turns of the encoder shaft – an example of this is lead and ball screw applications.


Resolution

The resolution of the encoder is dependent on the number of tracks on the code disk. Each track requires a wire (pin connection) for the output signal for that bit. Ten-bit resolution is 1024 counts per turn.

Example: 2 to the 10th = 1024