Emerson Rosemount 644 Reference Manual page 24

Configuration
March 2021
2.6.3 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 LOI.
To utilize this feature properly perform the following steps:
Procedure
1. Measure the lead wire resistance of both RTD leads after installing the 2-wire RTD
2. Navigate to the 2-wire RTD Offset parameter.
3. Enter the total measured resistance of the two RTD leads at the 2-wire Offset
Set 2-wire RTD offset using the Field Communicator
From the HOME screen, enter the Fast Key sequence.
Device Dashboard Fast Keys
Set 2-wire RTD offset using the AMS Device Manager
Procedure
1. Right click on the device and select Configure.
2. In the left navigation pane select Manual Setup and select the Sensor 1 or Sensor 2
3. Select Apply when complete.
24
and transmitter.
prompt to ensure proper adjustment. The transmitter will adjust its temperature
measurement to correct the error caused by lead wire resistance.
tab depending on the need. Find the 2-wire offset text field and enter the value.
2, 1, 1
Reference Manual
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