Rockwell Automation 1797-IRT8 FLEX Ex Thermocouple/RTD/mV Input Module User Manual - Manual (Page 19)

Publication 1797-6.5.2 - February 2001
Understanding Configurable FLEX Ex Thermocouple/RTD/mV Input Module Features 2-5
Sensor Mode Select
Selects the sensor mode for input channels 0-3 and 4-7.
If using cold junction compensation, both CJCs must be installed. The
difference between the CJCs will be linearly apportioned to each
thermocouple channel based on its position across the base. If one
CJC is broken or missing, the remaining CJC is used to compensate all
channels. The appropriate CJC alarm will be set in this case. If the
second CJC fails, the last valid reading is frozen for compensation use.
The second CJC alarm will also be set.
When using only channels 0-3 for thermocouples, connect the CJCs to
terminals 5 and 12. If only using channels 4-7, connect the CJCs to
terminals 22 and 29. If all channels are configured for thermocouples,
connect the CJCs to terminals 5 and 29.
When CJC thermistor temperature compensation is selected for one
channel group, all channels configured for thermocouple inputs will
use the CJC compensation.
Preset Temperature Select
This parameter is used if Input Type Select is set to thermocouple and
Sensor Mode Select is set to fixed compensation. This parameter then
sets a fixed reference temperature used to compensate all
thermocouple channels.
The default = 0.
Bit
05 04 Sensor mode for channels 0 thru 3
13 12 Sensor mode for channels 4 thru 7
Thermocouple Mode
0 0 External compensation - uses cold junction sensors
0 1 Internal compensation - Uses the value selected for reference junction
1 0
No compensation (Data is referenced to 0
o
C)
1 1 Differential measurement between 2 channels
RTD Mode
0 0 2-wire RTD - no compensation
0 1 2-wire RTD with user compensation
1 0 3-wire RTD
1 1 4-wire RTD