Emerson Rosemount 644 HART, Reference Manual

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68
Reference Manual
00809-0100-4728, Rev MB
Operation and Maintenance
July 2016
Operation and Maintenance
Table 5-2. Standard RTD vs. RTD with Matched CVD Constants with Enhanced Transmitter
Accuracy Option P8
Callendar-Van Dusen equation
The following input variables, included with specially-ordered Rosemount temperature sensors, are
required:
R
t
= R
o
+ R
o
a [t – d(0.01t-1)(0.01t) – b(0.01t – 1)(0.01t)
3
]
R0 = Resistance at Ice Point
Alpha = Sensor Specific Constant
Beta = Sensor Specific Constant
Delta = Sensor Specific Constant
To input Callendar-Van Dusen constants, perform one the following procedures:
Entering CVD constants using Field Communicator
Entering CVD constants using AMS Device Manager
1. Right click on the device and select Configure .
2. In the left navigation pane choose Manual Setup and choose the Sensor 1 or Sensor 2 tab
depending on the need.
3. Find the Transmitter Sensor Matching (CVD) group box and enter in the required CVD constants. Or
click the Set CVD Coefficients button to be guided through steps. You may also click the Show CVD
Coefficients button to see the current coefficients loaded into the device.
4. Click Apply when complete.
Note
When the transmitter-senor matching is disabled, the transmitter reverts to either user or factory trim,
whichever was used previously. Make certain the transmitter engineering units default correctly before
placing the transmitter into service.
System accuracy comparison at 150 °C using a PT 100 (

=0.00385)
RTD with a span of 0 to 200 °C
Standard RTD Matched RTD
Rosemount 644 ±0.10 °C Rosemount 644 ±0.10 °C
Standard RTD ±1.05 °C Matched RTD ±0.18 °C
Total System
(1)
1. Calculated using root-summed-squared (RSS) statistical method
±1.05 °C Total System
(1)
±0.21 °C
From the HOME screen, enter the Fast Key sequence
Device Dashboard Fast Keys
2, 2, 1, 9
TotalSystemAccuracy TransmitterAccuracy
  2
SensorAccuracy
  2
+ =