Rockwell Automation 1746-BTM Barrel Temperature Control Module User Manual - Manual (Page 23)

Publication 1746-UM010B-EN-P - April 2001
Installing and Wiring 2-7
Figure 2.2 Thermistor placement on the bottom of the terminal block
Wiring considerations
Follow the guidelines below when planning your system wiring.
•
To limit the pickup of electrical noise, keep thermocouple and
millivolt signal wires away from power and load lines.
•
For high immunity to electrical noise, use Alpha 5121 (shielded,
twisted pair) or equivalent wire for millivolt sensors; or use
shielded, twisted pair thermocouple extension lead wire
specified by the thermocouple manufacturer. Using the incorrect
type of thermocouple extension wire or not following the
correct polarity may cause invalid readings. See IEEE Std. 518,
Section 6.4.2.7 or contact your sensor manufacturer for
additional details.
•
When trimming cable leads, minimize the length of unshielded
wires.
•
Ground the shield drain wire at only one end of the cable. The
preferred location is at the I/O chassis ground (See Figure 2.4).
•
For maximum noise reduction, use 3/8 inch braid wire to
connect cable shields to the nearest I/O chassis mounting bolt.
Then connect the I/O chassis to earth ground (See Figure 2.4).
These connections are a requirement regardless of cable type.
•
Tighten terminal screws. Excessive tightening can strip the
screw.
•
The open–circuit detector generates approximately 20 nano–
amperes into the thermocouple cable. A total lead resistance of
25 ohms (12.5 one–way) will produce 0.5 mV of error.
•
Follow system grounding and wiring guidelines found in your
SLC 500 Modular Hardware Installation and Operation Manual,
publication 1747–6.2.
Always attach red
lug to the CJC+
terminal