Grounding, Cable lengths – Rockwell Automation 1771-IXE Installation Instructions User Manual
Page 6

Thermocouple/Millivolt Input Module
6
Publication 1771Ć5.64 - October 1998
Cable Lengths
Recommended maximum cable length for voltage-mode input
devices is 50 feet, due to possible signal degradation and electrical
noise immunity in typical industrial environments.
When using shielded cable or shielded thermocouple extension wire,
ground the foil shield and drain wire only at one end of the cable. We
recommend that you wrap the foil shield and drain wire together, and
connect them to a chassis mounting bolt, grounding stud or chassis
single-point grounding point. Use heat shrink tubing to seal the exit
point of the wires. At the opposite end of the cable, tape exposed
shield and drain wire with electrical tape to insulate it from electrical
contact.
Remove a length of cable
jacket from the thermocouple
cable.
Pull the foil shield and bare
drain wire from the insulated
wires. Bare drain
wire
Insulated
wires
Foil
shield
Twist the foil shield and drain
wire together to form a single
strand.
Attach a ground lug, and apply
heat shrink tubing to the exit area.
20104
Belden 8761 Cable
Length as needed
Cable Grounding
1
19480
Grounding Stud
1
Use the cup washer if crimpĆon lugs are not used.
Chassis Ground
Ground Lug
Ground Lug
1
Star
Washer
I/O Chassis
Side Plate
Nut and Captive
Washer
ExternalĆtooth Washers
#10 ThreadĆforming screw
19923
Shield and Drain
twisted together
Shield and Drain
twisted together
SingleĆpoint Grounding
Extend shield to termination point. Expose just enough cable to
adequately terminate inner conductors.
Use heat shrink tubing or
other suitable insulation
where wire exits cable jacket.
Nut
When you connect grounding conductors to the I/O chassis
grounding stud, place a star washer under the first lug, then
place a nut with captive lock washer on top of each ground lug.
2
Refer to Industrial Automation Wiring and Grounding Guidelines for Noise Immunity, publication 1770Ć4.1 for additional information.
Grounding