Allen-Bradley MicroLogix 1200, Руководство пользователя, Страница: 29 / 144

Publication 1762-UM002A-EN-P - July 2002
Installation and Wiring 2-13
Wiring Diagram
Cold Junction
Compensation To obtain accurate readings from each of the channels, the
temperature between the thermocouple wire and the input channel
must be compensated for. A cold junction compensating thermistor
has been integrated in the terminal block. The thermistor must remain
installed to retain accuracy.
If the thermistor assembly is accidentally removed, re-install it by
connecting it across the pair of CJC terminals.
IN 0+
IN 0-
IN 2+
IN 1 +
IN 2-
IN 1-
IN 3+
IN 3-
+
-
+
-
+
-
CJC+
CJC -
within 10V dc
grounded thermocouple
grounded thermocouple
ungrounded thermocouple
CJC sensor
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.
ATTENTION
!
Do not remove or loosen the cold junction
compensating thermistor assembly. This assembly is
critical to ensure accurate thermocouple input
readings at each channel. The module will operate
in the thermocouple mode, but at reduced accuracy
if the CJC sensor is removed. See Determining
Open-Circuit Response (Bits 6 and 5) on page 3-9.
AB Parts