Sensor Input Trim - Emerson Rosemount 648 Reference Manual

Configuration
July 2016
2.8.1

Sensor input trim

Fast Key sequence
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.
2.
3.
4.
Note
It is recommended to perform lower offset trims first, before performing upper slope trims.
5.
6.
7.
8.
9.
18
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3, 5, 2
Connect the calibration device or sensor to the transmitter. Refer to
page 6 or on the device terminal block for sensor wiring diagrams.
Connect the communicator to the transmitter.
From the Home screen, select 3 Service Tools> 5 Maintenance> 2 Calibration to
prepare to trim the sensor.
Select 6 Lower Sensor Trim or 7 Upper Sensor Trim.
Answer the question about using an active calibrator or not.
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.
Select OK once the temperature stabilizes. The communicator displays the output
value the transmitter associates with the input value provided by the calibration
device.
Select the appropriate sensor trim units at the prompt.
Enter the trim point.
Reference Manual
00809-0200-4648, Rev BB
Figure 2-1 on
Configuration