18
Reference Manual
00809-0200-4648, Rev BB
July 2016
2.8.1
Sensor input trim
Perform a sensor trim if the transmitters digital value for the primary variable does not
match the plant’s standard calibration equipment. The sensor trim function calibrates the
sensor to the transmitter in temperature units or raw units. Unless your site-standard input
source is NIST-traceable, the trim functions will not maintain the NIST-traceability of the
system.
The
Sensor Input Trim
command allows the transmitter’s interpretation of the input signal to
be digitally altered. The sensor reference command trims, in engineering (
F,
C,
R, K) or
raw (
, mV) units, the combined sensor and transmitter system to a site standard using a
known temperature source. Sensor trimming is suitable for validation procedures or for
applications that require calibrating the sensor and transmitter together.
Use the following procedure to perform a sensor trim with a Rosemount 648 Wireless:
1.
Connect the calibration device or sensor to the transmitter. Refer to
or on the device terminal block for sensor wiring diagrams.
2.
Connect the communicator to the transmitter.
3.
From the
Home
screen, select
3 Service Tools> 5 Maintenance> 2 Calibration
to
prepare to trim the sensor.
4.
Select
6 Lower Sensor Trim
or
7 Upper Sensor Trim.
Note
It is recommended to perform lower offset trims first, before performing upper slope trims.
5.
Answer the question about using an active calibrator or not.
6.
Adjust the calibration device to the desired trim value (must be within the selected
sensor limits). If a combined sensor and transmitter system are being trimmed,
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.
7.
Select
OK
once the temperature stabilizes. The communicator displays the output
value the transmitter associates with the input value provided by the calibration
device.
8.
Select the appropriate sensor trim units at the prompt.
9.
Enter the trim point.
Fast Key sequence
3, 5, 2
Содержание Rosemount X-well 648
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