Emerson Rosemount 248 Reference Manual page 48

Operation and Maintenance
May 2019
Figure 4-2: Standard vs. Actual Sensor Curve
Note
The Actual Curve is identified from the Callendar-Van Dusen equation.
Matching the specific sensor curve with the transmitter significantly enhances the
temperature measurement accuracy. See the comparison below in
Table 4-1: Standard RTD vs. RTD with Matched CVD Constants
System accuracy comparison at 150 °C using a PT 100 (α =0.00385) RTD with a span of 0 to
200 °C
Standard RTD
Rosemount 248
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
R0 = Resistance at Ice Point
Alpha = Sensor Specific Constant
Beta = Sensor Specific Constant
48
(1)
+ R α [t – δ(0.01t-1)(0.01t) – β(0.01t – 1)(0.01t)
o o
Matched RTD
±0.15 °C Rosemount 248
±1.05 °C Matched RTD
±1.06 °C Total System
3
Rosemount 248 Temperature Transmitter Reference Manual
Reference Manual
00809-0100-4825
Table 4-1.
±0.15 °C
±0.18 °C
(1)
±0.23 °C
]