Setting Output Units - Emerson Rosemount 644 Reference Manual

Section 2: Configuration
April 2015
Contact an Emerson Process Management representative for information on the temperature
sensors, thermowells, and accessory mounting hardware that is available through Emerson
Process Management.
2-wire RTD offset
The 2-wire offset feature allows the measured lead wire resistance to be input and corrected for,
which results in the transmitter adjusting its temperature measurement for the error caused by
this added resistance. Because of a lack of lead wire compensation within the RTD, temperature
measurements made with a 2-wire RTD are often inaccurate.
This feature can be configured as a subset of the Sensor Configuration process in the Field
Communicator, AMS Device Manager, and the Local Operator Interface.
To utilize this feature properly perform the following steps:
1.
2.
3.
Enter 2-wire offset with Field Communicator
From the HOME screen, enter the Fast Key sequence.
Device Dashboard Fast Keys
Enter 2-wire offset with AMS Device Manager
1.
2.
3.
2.6.3

Setting output units

The Units can be configured for a number of different parameters in the 644. Individual Units
can be configured for:
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18
Measure the lead wire resistance of both RTD leads after installing the 2-Wire RTD and
644.
Navigate to the 2-Wire RTD Offset parameter.
Enter the total measured resistance of the two RTD leads at the 2-Wire Offset prompt
to ensure proper adjustment. The transmitter will adjust its temperature measurement
to correct the error caused by lead wire resistance.
Right click on the device and select Configure.
In the left navigation pane select Manual Setup and select the Sensor 1or Sensor 2 tab
depending on the need. Find the 2-Wire Offset text field and enter the value.
Select Apply when complete.
Sensor 1
Sensor 2
Terminal Temperature
Differential Temperature
Average Temperature
First Good Temperature
2, 1, 1
Reference Manual
00809-0200-4728, Rev RA
Configuration