Rockwell Automation 1762-IT4 Thermocouple/mV Input Module - Manual (Page 12)

12 MicroLogix 1200 Thermocouple/mV Input Module
Publication 1762-IN013B-EN-P - June 2013
Terminal Block with CJC Sensor and Thermocouple Junctions
Cold Junction Compensation (CJC)
To obtain accurate readings from each of the channels, the temperature at the terminal junction
between the thermocouple wire and the input channel must be compensated for. A cold junction
compensating thermistor has been integrated in the terminal block, as shown on page 12.
TIP
When using an ungrounded thermocouple, the shield must be
connected to ground at the module end.
IMPORTANT
When using grounded and/or exposed thermocouples that are touching
electrically conductive material, the ground potential between any two
channels cannot exceed ±10V DC, or temperature readings will be
inaccurate and the module may be damaged.
ATTENTION
Do not remove or loosen the cold junction compensating thermistor
assembly on the terminal block. The thermistor assembly is critical to
ensure accurate thermocouple input readings at each channel. If the CJC
sensor is removed, the open-circuit detection bit (OC4) and the general
status bit (S4) are set. The module will continue to operate, but with
reduced accuracy.
IN 0+
IN 0-
IN 2+
IN 1 +
IN 2-
IN 1-
IN 3+
IN 3-
+
-
+
-
+
-
CJC+
CJC -
within 10V DC
grounded thermocouple
ungrounded
thermocouple
CJC sensor grounded thermocouple