how many types of encoder there

snipped-for-privacy@gmail.com wrote in news:1181988818.987829.52610 @q19g2000prn.googlegroups.com:

It depends what you are encoding. Is it one data form to another?

audio/video?

Some physical property?

It can be endless.

Is this a pop quiz ? How about an incremental type of encoder?, they come in various forms. A,B,Z/ A+,A- B+,B-, Z etc (Q Types) then you have some that only has one output pulse. A = main pulse, B or the Q signal is an offset from A so that direction can be detected.

The +/- types give you more precise indexing with out the higher speeds that would normally be required on a single output. Z is the zero point.. In some systems, especially those that use the +/- with Z, the equipment has an auto tune function to detect the PPR of the encoder via the Z signal, and uses the +/- outputs in calculating the position of the rotor of an AC motor for example, so that better tracking can be had, when controlling the speed of an AC motor. Normally drives that need this kind of tuning requires you to disconnect the motor shaft from it's load so that the drive can properly calculate encoder's position with the rotor so it can generate a consistent torque..

Then there's the Gray code types. those are parallel outputs and used for Absolute positioning. They come in different output bit sizes but in any of them, the whole idea is to make sure no 2 or more bits get changed in their state at the same time other wise. This would cause problems where 2 bits may not trigger properly at the same time, thus giving you an erratic values whilst switching over to the next position. The end results is a value that ranges from 0..16 for example, in a 4 bit type, in a complete turn. etc..