Reference Manual
00809-0100-4021, Rev FB
August 2011
4-23
Rosemount 3144P
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Fieldbus Diagnostics
Thermocouple Degradation Diagnostic
Thermocouple Degradation Diagnostic acts as a gauge of general
thermocouple health and is indicative of any major changes in the status of
the thermocouple or the thermocouple loop. The transmitter monitors the
resistance of the thermocouple loop to detect drift conditions or wiring
condition changes. The transmitter uses a baseline and threshold Trigger
value and reports the suspected status of the thermocouple. This feature is
not intended to be a precise measurement of thermocouple status, but is a
general indicator of thermocouple and thermocouple loop health.
Thermocouple diagnostic must be connected, configured, and enabled to
read a thermocouple. Once the diagnostic has been activated, a Baseline
resistance value is calculated. Then a threshold Trigger must be selected,
which can be two, three, or four times the Baseline resistance, or the default
of 5000 ohms. If the thermocouple loop resistance reaches the Trigger Level,
a maintenance alert is generated.
CAUTION
The Thermocouple Degradation Diagnostic monitors the health of the entire
thermocouple loop, including wiring, terminations, junctions, and the sensor
itself. Therefore, it is imperative that the diagnostic baseline resistance be
measured with the sensor fully installed and wired in the process, and not on
the bench.
NOTE
The thermocouple resistance algorithm does not calculate resistance values
while the active calibrator mode is enabled.
Aotewell Ltd
www.aotewell.com
Industry Automation
HongKong|UK|China
+86-755-8660-6182
