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Reference Manual
00809-0200-4728, Rev RA
Section 5: Operation and Maintenance
April 2015
Operation and Maintenance
Performing an analog output trim using AMS Device Manager
1. Right click on the device and select Service Tools.
2. In the left navigation pane select Maintenance.
3. Find the Analog Calibration tab and select the Scaled Trim button.
4. Follow the screen prompts 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 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 Tabl e 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 (α=0.00385)
RTD with a span of 0 to 200 °C
Standard RTD Matched RTD
644 ±0.15 °C 644 ±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
Resistance, Ohm
0 °C
(1) The Actual Curve is identified from the Callendar-Van Dusen equation.
TotalSystemAccuracy TransmitterAccuracy()
2
SensorAccuracy()
2
+=
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