Rockwell Automation 1746-HSCE2 Multi-Channel High-Speed Counter Installation Instructions - Manual (Page 9)

Multi-Channel High-Speed Counter 9
Publication 1746-IN002A-US-P
Important Wiring Considerations
Use the following guidelines when planning the system wiring for the module:
• Install the SLC 500 system in a NEMA-rated enclosure.
• Disconnect power to the SLC processor and the module before wiring.
• Make sure the system is properly grounded.
• Group this module and low-voltage DC modules away from AC I/O or
high-voltage DC modules.
• Shielded cable is required for high-speed input signals A, B, and Z. Use
individually shielded, twisted pair cable lengths up to 300 m (1000 ft.).
• Shields should be grounded only at one end. Ground the shield wire outside
the module at the chassis mounting screw. Connect the shield at the encoder
end only if the housing is isolated from the motor and ground.
• If you have a junction in the cable, treat the shields as a conductor at all
junctions. Do not ground them to the junction box.
Considerations for Reducing Noise
In high noise environments, the 1746-HSCE2 inputs may accept “false” pulses,
particularly when using low frequency input signals with slowly sloping pulse
edges. To minimize the effects of high frequency noise on low frequency signals,
the user can do the following:
• Identify and remove noise sources.
• Route 1746-HSCE2 input cabling away from noise sources.
• Install low pass filters on input signals. Filter values are dependent on the
application and can be determined empirically.
• Use devices which output differential signals, like differential encoders, to
minimize the possibility that a noise source will cause a false input.