Rockwell Automation 1762-IT4 Thermocouple/mV Input Module - Manual (Page 8)

8 MicroLogix 1200 Thermocouple/mV Input Module
Publication 1762-IN013B-EN-P - June 2013
Field Wiring Connections
Grounding the Module
This product is intended to be mounted to a well-grounded mounting surface such as a metal
panel. Additional grounding connections from the module’s mounting tabs or DIN rail, are not
required unless the mounting surface cannot be grounded. Refer to Industrial Automation
Wiring and Grounding Guidelines, Allen-Bradley publication
1770-4.1 , for additional
information.
System Wiring Guidelines
Consider the following when wiring your system:
• Do not tamper with or remove the CJC sensor on the terminal block. Removal of the
sensor will reduce accuracy and set the open circuit bit for the CJC sensor.
• For thermocouple inputs, always use shielded, twisted-pair thermocouple extension lead
wires specified by the thermocouple manufacturer for the themocouple type you are
using. Using an incorrect thermocouple extension wire type or not following correct
polarity convention will cause invalid readings.
• Keep cable shield connection to ground as short as possible.
• To limit noise, keep thermocouple and millivolt signal wires as far away as possible from
power and load lines as well as other sources of electrical noise, such as motors,
transformers, contactors, and AC devices.
• If the field wiring must cross AC or power cables, ensure that they cross at right angles.
• For millivolt inputs, always use Belden™ 8761 (shielded, twisted-pair) or equivalent wire
to ensure proper operation and high immunity to electrical noise.
• If multiple power supplies are used with millivolt analog inputs, the power supply
commons must be connected.
ATTENTION The possibility exists that grounded or exposed thermocouples can
become shorted to a potential greater than that of the thermocouple
itself. Due to possible shock hazard, care should be taken when wiring
these types of thermocouples.