encoders???

hi everyone

anyone who's familiar with encoders?
i need some help with the following:
1. whats the relevenace of the phase z output of an encoder?
how can i make use of it in my plc pgm?
2. deviation counter reset (+ECRST, -ECRST)
everytime i execute an origin or homing (servo motor), do i have to reset
this counter?

any related/additional inputs are greatly appreciated.

Here is a good source:

http://www.patchn.com/basicencoder.htm

And one more:

http://www.feedbackdevices.com/uploadedFiles/Products/Danaher_Encoder_Handbook.pdf

I am not sure which encoder brand and model you were refering to. But let me just try to help here.
The Z pulse is a Position reference pulse, which mean it inidicate a distint location, normally one location per revolution of the encoder. This pulse is use for homing purpose where the Z pulse position is normally where the system Reset the position counter to "0" count after the homing sensore are detected. Therefore to answer your 2nd question, the homing program should check for homing sensor signal first, then check for z pulses location and once detected the Z pulse, reset the position counter, normally to value "0".
Hope that would help.