User manual

Publication CIG-WD001B-EN-P - May 2005
9-10 1762 I/O on MicroLogix 1200 Controllers
EXC 2
SENSE 2
RTN 2
NC
Belden 9501 Shielded Cable
Cable Shield (to Ground)
RTD EXC
Return
RTD EXC
Return
IMPORTANT: Using 2-wire configurations does not permit the module to compensate
for resistance error due to lead wire length. The resulting analog
data includes the effect of this uncompensated lead wire resistance.
The module continues to place the uncompensated analog data in
the input data file, but the open-circuit status bit (OCx) is set in word 4
of the input data file for any enabled channel using a 2-wire
configuration. These status bits may be used in the control program
to indicate that the analog data includes error due to uncompensated
lead wires.
EXC 2
SENSE 2
RTN 2
NC
Belden 83503 or 9533 Shielded Cable
Cable Shield (to Ground)
RTD EXC
Sense
RTD EXC
Return
Sense
Return
EXC 2
SENSE 2
RTN 2
NC
Belden 83503 or 9533 Shielded Cable
Leave one sensor wire open.
Cable Shield (to Ground)
RTD EXC
Return
RTD EXC
Return
Sense
Sense
1762-IR4 2-Wire RTD 1762-IR4 3-Wire RTD
1762-IR4 4-Wire RTD
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
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.
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.
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.
TIP:
When using an ungrounded thermocouple, the shield must be connected at the module end.
1762-IT4