Reference Manual
00809-0100-4021, Rev FB
August 2011
Rosemount 3144P
3-32
HART
5. The communicator will ask “Are you using an active calibrator?”
a. Select “No” if a sensor is connected to the transmitter.
b. Select “Yes” if using a calibration device. By selecting yes, the
transmitter will switch into active calibration mode (see “Active
Calibrator and EMF Compensation” ). This is critical if the calibrator
requires constant sensor current for calibration. If using a calibration
device that can accept pulsed current, select “No.”
6. Select the appropriate sensor trim units at the ENTER SNSR 1 TRIM
UNITS prompt.
7. Select 1 Lower Only, 2 Upper Only, or 3 Lower and Upper at the
SELECT SENSOR TRIM POINTS prompt.
8. Adjust the calibration device to the desired trim value (must be within the
selected sensor limits). If trimming a combined sensor and transmitter
system, expose the sensor to a known temperature and allow the
temperature reading to stabilize. Use a bath, furnace, or isothermal
block, measured with a site-standard thermometer, as the known
temperature source.
9. Select OK once the temperature stabilizes.
10. Enter the lower or upper trim point, depending on your selection in
Step 7.
To trim the second sensor, repeat the same procedure except in Step 4, select
the sensor not yet calibrated (usually Sensor 2).
Active Calibrator and
EMF Compensation
The transmitter operates with a pulsating sensor current to allow EMF
compensation and detection of open sensor conditions. Because some
calibration equipment requires a steady sensor current to function properly,
the “Active Calibrator Mode” feature should be used when an Active
Calibrator is connected. Enabling this mode temporarily sets the transmitter to
provide steady sensor current unless two sensor inputs are configured.
Disable this mode before putting the transmitter back into the process to set
the transmitter back to pulsating current. “Active Calibrator Mode” is volatile
and will automatically be disabled when a Master Reset is performed (through
HART) or when the power is cycled.
EMF compensation allows the transmitter to provide sensor measurements
that are unaffected by unwanted voltages, typically due to thermal EMFs in
the equipment connected to the transmitter, or by some types of calibration
equipment. If this equipment also requires steady sensor current, the
transmitter must be set to “Active Calibrator Mode.” However, the steady
current does not allow the transmitter to perform EMF compensation and as a
result, a difference in readings between the Active Calibrator and actual
sensor may exist.
If a reading difference is experienced and is greater than the plant’s accuracy
specification allows, perform a sensor trim with “Active Calibrator Mode”
disabled. In this case, an active calibrator capable of tolerating pulsating
sensor current must be used or the actual sensors must be connected to the
transmitter. When the Field Communicator or AMS asks if an Active Calibrator
is being used when the sensor trim routine is entered, select No to leave the
“Active Calibrator Mode” disabled.
Contact an Emerson Process Management representative for more
information.
Traditional Fast Keys 1, 2, 2, 1, 3
Device Dashboard
Fast Keys
3, 4, 1, 7
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