Emerson Rosemount 3144P, Reference Manual

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159
Reference Manual
00809-0100-4021, Rev JA
Configuration
April 2017
Configuration
Recall factory trim
To recall a factory trim on the transmitter, run the recall factory trim. If your system does not support
methods, manually configure the transducer block parameters listed below.
1. Set MODE_BLK.TARGET_X to OOS.
2. Set SENSOR_CAL_METHOD_X to Factory Trim.
3. Set SET_FACTORY_TRIM_X to Recall.
4. Set SENSOR_CAL_DATE_X to the current date.
5. Set SENSOR_CAL_WHO_X to the person responsible for the calibration.
6. Set SENSOR _CAL_LOC_X to the calibration location.
7. Set MODE_BLK.TARGET_X to AUTO.
Note
When changing the sensor type, the transmitter reverts to the factory trim and any other trim
performed on the transmitter is lost.
4.10.3 Advanced 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 for increasing resistance of the thermocouple loop to detect drift conditions or wiring
condition changes. The degrading thermocouple can be caused by wire thinning, sensor breakdown,
moisture intrusion or corrosion and can be an indication of an eventual sensor failure.
How it works:
The thermocouple degradation diagnostic measures the amount of resistance on a thermocouple sensor
path. Ideally a thermocouple would have zero resistance, but in reality it has some resistance especially
for long thermocouple extension wires. As the sensor loop degrades (including sensor degradation and
wire or junctions degradation), the resistance of the loop increases. First, the transmitter is configured to
a baseline by the user. Then, at least once per second, the degradation diagnostic monitors the
resistance in the loop by sending a pulsed current (in microamps) on the loop, measuring the voltage
induced and calculating the effective resistance. As the resistance increases, the diagnostic can detect
when the resistance exceeds the threshold set by the user at which the diagnostic will provide a digital
alert. This feature is not intended to be a precise measurement of thermocouple status, but is a general
indicator of thermocouple and thermocouple loop health by providing trending over time.
The thermocouple degradation diagnostic does not detect shorted thermocouple conditions.
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.
Important
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.