Rockwell Automation 1797-IRT8 FLEX Ex Thermocouple/RTD/mV Input Module User Manual - Manual (Page 12)

Publication 1797-6.5.2 - February 2001
1-4 About the FLEX Ex Thermocouple/RTD/mV Input Module
Data Format Alarm Example
In this example, the normal active data range is 4-20mA. The alarms
are generated in three overlapping bands.
Overrange
If the input is greater than the maximum temperature of the
thermocouple or RTD range, millivolt (+100mV), or resistance (500W)
the overrange bit for that channel will be set.
Underrange
If the input is less than the minimum temperature of the thermocouple
or RTD range, millivolt (-40mV), or resistance (0W) the underrange bit
for that channel will be set.
Open Wire
Individual channel fault alarm for broken wire. If a broken wire/
detached lead is detected, the data value is forced to maximum. In
RTD/W mode, input levels above 540W will set this bit; in
thermocouple/mV mode, input levels above 210mV will set this bit.
Cold Junction Compensation Alarm
Broken or detached lead or shorted lead detection is included for
CJCs. This detection is only available when the input type selected is
thermocouple and sensor mode is set to CJC compensation.
When either CJC fails its fault is reported. Both CJCs ae normally used
in compensation calculations. If one CJC fails, calculations use the
remaining good device. If both fail, calculations use the last good
value.
normal signal range overrange
CJC fault
underrange
Minumum
Value for
Sensor
Type
Maximum
Value for
Sensor
Type
Maximum
Measureable
Value
PHYSICAL INPUT SIGNAL RANGE
Channel Data
Forced to
Maximum for Type
CJC fault
open wire fault