The RMC quadrature encoder inputs require 5V differential (RS-422) signals. If your encoder has a higher voltage level, such as 24V, you can use the following device to convert the signal to the correct 5V differential level. This device also provides optical isolation. Notice that there are several part numbers. The one below is for converting 24V signals levels to 5V. Some other versions of these BEI converters can be used to convert encoders with Open Collector outputs to RS-422 signals.
Sensata Optical Isolator Module
Part number: EM-DR1-IC-24-TB-28V/5 (60001-011)
http://www.sensata.com
Automation Direct
Part number: FC-ISO-D
“Signal conditioner, isolated, differential or single ended line driver input, differential line driver output, 24 VDC operating voltage, 35mm DIN rail or panel mount, removable screw terminal plugs.”
http://www.automationdirect.com/
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