Emerson Rosemount 644 Reference Manual page 85

Reference Manual
00809-0200-4728, Rev RA
Table 5-2. Standard RTD vs. RTD with Matched CVD Constants with Enhanced Transmitter
System Accuracy Comparison at 150 °C Using a PT 100 (α=0.00385)
Standard RTD
644
Standard RTD
Total System
(1) Calculated using root-summed-squared (RSS) statistical method
Callendar-Van Dusen equation:
The following input variables, included with specially-ordered Rosemount temperature sensors,
are required:
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 a Field Communicator
From the HOME screen, enter the Fast Key sequence.
Device Dashboard Fast Keys
Entering CVD constants using AMS Device Manager
1.
2.
3.
4.
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.
Operation and Maintenance
Accuracy Option P8
RTD with a Span of 0 to 200 °C
±0.10 °C
±1.05 °C
(1)
±1.05 °C
(
TotalSystemAccuracy =
R = R + R α [t – δ(0.01t-1)(0.01t) – β(0.01t – 1)(0.01t)
t o o
Right click on the device and select Configure.
In the left navigation pane choose Manual Setup and choose the Sensor 1 or Sensor 2
tab depending on the need.
Find the Transmitter Sensor Matching (CVD) group box and enter in the required CVD
constants. Or select "Set CVD Coefficients" button to be guided through steps. You
may also select "Show CVD Coefficients" button to see the current coefficients loaded
into the device.
Select Apply when complete.
Section 5: Operation and Maintenance
Matched RTD
644
Matched RTD
(1)
Total System
) 2 (
TransmitterAccuracy + SensorAccuracy
2, 2, 1, 9
April 2015
±0.10 °C
±0.18 °C
±0.21 °C
) 2
3
]
75