Getting 8000CPR out of a 2000 line encoder? (answered)

[martyscncgarage]

How do you get 8000 counts per rev out of a 2000 line encoder???

I have been getting asked this question as a result of a one of my videos.
Dynapar (Makers of great industrial encoders) explains it well here:
http://www.dynapar.com/Technology/Encod ... e_Encoder/

Marty

[diycncscott]

On a quadrature encoder, there are 4 pulses generated. 1 ea for A, A-, B and B- for each "line" - hence the "quad"

[Centroid_Tech]

On a typical encoder, you have 2 signals, A and B. Each individual signal has 2 states that it can be in, either ON or OFF. Since you have 2 signals that have 2 independent states, there are 4 possible combinations for those signals - They can both be ON, they can both be OFF, or one of them can be ON. The attached photo shows the logic table of those signals. The ON state is represented by a logic 1 while the OFF state is represented by a logic 0. That is why you multiply the line count or ppr of an encoder by 4.

[frijoli]

On a typical encoder, you have 2 signals, A and B. Each individual signal has 2 states that it can be in, either ON or OFF. Since you have 2 signals that have 2 independent states, there are 4 possible combinations for those signals - They can both be ON, they can both be OFF, or one of them can be ON. The attached photo shows the logic table of those signals. The ON state is represented by a logic 1 while the OFF state is represented by a logic 0. That is why you multiply the line count or ppr of an encoder by 4.

The cool thing is it uses that format to determine which direction it is rotating. Each state happens in the exact order forward or back. In one pulse it know which way it's moving.

Clay

[martyscncgarage]

Everyone's input on this one is appreciated! Explained several different ways!
Marty