I have r990h boards and Renco CA18 encoders http://www.renco.com/106021.htm (no longer made) but after many reincarnations the pins are starting to be faulty. I want to change them , what is Rutex recommendation on which encoders to use and not to use.
US Digital encoders are good and reliable. If you get the single ended encoder, our little R2210 adapters make hook up very easy. You hook up 5 wires to the adapter and plug in a shielded cat5 cable into the drive and the adapter and you are done!
CUI sells a nice little encoder for motors with 3/8 in shafts and smaller:
Price is 30.00 from Digi-key corp.
Part number is AMT-102v, I believe. Be sure to ask for the number for the 1 ft pigtail cable to hook to the R2210 adapter. It is dip switch selectable output between about 32 lines to 2000 or so. It comes with a set of bushings to adapt to many shaft sizes.
Don't try to make your own cable. It is picky about the correct connector on it. I think the cable is just a few bucks.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)