GE AF-650 GP Operating Instructions Manual page 51

Installation
Very long control cables and analogue signals may in rare
cases and depending on installation result in 50/60Hz
earth loops due to noise from mains supply cables.
If this occurs, it may be necessary to break the screen or
insert a 100nF capacitor between screen and chassis.
3 3
The digital and analog inputs and outputs must be
connected separately to the drive common inputs
(terminal 20, 55, 39) to avoid earth currents from both
groups to affect other groups. For example, switching on
the digital input may disturb the analog input signal.
Input polarity of control terminals
NOTE
Control cables must be screened/armoured.
50
AF-650 GP High Power Operating Instructions
Connect the wires as described in the Operating
Instruction for the drive. Remember to connect the shields
in a proper way to ensure optimum electrical immunity.