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About the FLEX Ex Thermocouple/RTD/mV Input Module
CJC fault
Publication 1797-6.5.2 - February 2001
Data Format Alarm Example
In this example, the normal active data range is 4-20mA. The alarms
are generated in three overlapping bands.
PHYSICAL INPUT SIGNAL RANGE
underrange
normal signal range
Minumum
Value for
Sensor
Type
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.
overrange
CJC fault
Maximum
Maximum
Value for
Measureable
Sensor
Value
Type
open wire fault
Channel Data
Forced to
Maximum for Type
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