Emerson Rosemount 644 Reference Manual page 94

Operation and Maintenance
March 2021
Matching the specific sensor curve with the transmitter significantly enhances the
temperature measurement accuracy. See the comparison below in
Table 5-1: Standard RTD vs. RTD with Matched CVD Constants with Standard
Transmitter Accuracy
Standard RTD
Rosemount 644
Standard RTD
Total System
(1) Calculated using root-summed-squared (RSS) statistical method.
Table 5-2: Standard RTD vs. RTD with Matched CVD Constants with Enhanced
Transmitter Accuracy Option P8
Standard RTD
Rosemount 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:
R = R
t
• R
0
• Alpha = Sensor specific constant
• Beta = Sensor specific constant
• Delta = Sensor specific constant
To input Callendar-Van Dusen constants, perform one the following procedures:
94
System accuracy comparison at 150 °C using a PT 100 (α=0.00385)
(1)
System Accuracy Comparison at 150 °C Using a PT 100 (α=0.00385)
(1)
+ R a [t – d(0.01t-1)(0.01t) – b(0.01t – 1)(0.01t)
o o
= Resistance at ice point
RTD with a span of 0 to 200 °C
Matched RTD
±0.15 °C Rosemount 644
±1.05 °C Matched RTD
±1.06 °C Total System
RTD with a Span of 0 to 200 °C
Matched RTD
±0.10 °C Rosemount 644
±1.05 °C Matched RTD
±1.05 °C Total System
3
Reference Manual
00809-0200-4728
Table 5-1.
±0.15 °C
±0.18 °C
(1)
±0.23 °C
±0.10 °C
±0.18 °C
(1)
±0.21 °C
]
Emerson.com/Rosemount