Rockwell Automation 1746-NT4 SLC 500 Thermocouple/mV Input Module Installation Instructions - Manual (Page 15)

SLC™ 500 4-Channel Thermocouple/mV Input Module 15
Publication 1746-IN010D-EN-P - June 2004
• Tighten terminal screws using a flat or cross-head screwdriver. Each screw
should be turned tight enough to immobilize the wire’s end. Excessive
tightening can strip the terminal screw. The torque applied to each screw
should not exceed 6 - 8 in-lbs (0.7 - 0.9 Nm) for each terminal.
• The open thermocouple detection circuit injects approximately
12 nanoAmperes into the thermocouple cable. A total lead resistance of
25
Ω (12.5 one-way) will produce 0.3 mV of error. To reduce error, use large
gauge wire with less resistance for long wire runs.
• Follow system grounding and wiring guidelines found in your SLC 500
Installation and Operation Manual, publication number 1747-6.21 (Fixed
Hardware Style) or 1747-UM011 (Modular Hardware Style).
Wiring Input Devices to the NT4
After the thermocouple module is properly installed in the chassis, follow the
wiring procedure below using the proper thermocouple extension cable, or
Belden 8761 for non-thermocouple applications.
To wire your NT4 module, follow these steps.
1. At each end of the cable, strip some casing to expose the individual wires.
2. Trim the signal wires to 2-inch lengths. Strip about 4.76 mm (3/16 inch) of
insulation away to expose the end of the wire.
3. At one end of the cable, twist the drain wire and foil shield together, bend
them away from the cable, and apply shrink wrap. Then earth ground at the
preferred location based on the type of sensor you are using (see wiring
guidelines on page 13).
Cable
Signal Wire
Signal Wire
Signal Wire
Signal Wire
Drain Wire
Foil Shield
(Twist together, shrink wrap, and
connect to earth ground.)
(Cut foil shield and
drain wire; then
insulate at cable
end.)