Emerson Rosemount 644 HART, Reference Manual

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67
Reference Manual
00809-0100-4728, Rev MB
Operation and Maintenance
July 2016
Operation and Maintenance
Using AMS Device Manager
1. Right click on the device and select Service Tools.
2. In the left navigation pane click on Maintenance .
3. Find the Analog Calibration tab and click on the Scaled Trim button.
4. Follow the screen prompts that will guide you through the analog trimming process.
5.6 Transmitter-Sensor Matching
Use Transmitter-Sensor Matching to enhance the temperature measurement accuracy of the system and
if you have a sensor with Callendar-Van Dusen constants. When ordered from Emerson Process
Management, sensors with Callendar-Van Dusen constants are NIST-traceable.
The Rosemount 644 accepts Callendar-Van Dusen constants from a calibrated RTD schedule and
generates a special custom curve to match that specific sensor Resistance vs. Temperature performance.
Figure 5-6 .
Figure 5-6. Standard vs. Actual Sensor Curve
Matching the specific sensor curve with the transmitter significantly enhances the temperature
measurement accuracy. See the comparison below in
Table 5-1 .
Table 5-1. Standard RTD vs. RTD with Matched CVD Constants with Standard Transmitter Accuracy
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 644H ±0.15 °C Rosemount 644H ±0.15 °C
Standard RTD ±1.05 °C Matched RTD ±0.18 °C
Total System
(1)
1. Calculated using root-summed-squared (RSS) statistical method
±1.06 °C Total System
(1)
±0.23 °C
Standard IEC 751
“Ideal” Curve
(1)
Actual Curve
Temperature, °C
R
e
sista
n
ce
, Ohm
0 °C
1. The Actual Curve is identified from the Callendar-Van Dusen equation.
TotalSystemAccuracy TransmitterAccuracy
 
2
SensorAccuracy
 
2
+ =