Emerson Rosemount - 3 Transmitter-Sensor Matching

125
Reference Manual
00809-0100-4021, Rev GC
Section 3: HART commissioning
April 2014
HART® commissioning
3.15.3 Transmitter-sensor matching
The 3144P 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. Matching the specific sensor curve with the transmitter significantly enhances the
temperature measurement accuracy. See the comparison below:
Problem description: Depending on the process being measured, a certain amount of
accuracy may be needed from the sensor.
Our solution: A more precise compensation for RTD inaccuracies is provided by Transmit-
ter-Sensor Matching using the transmitter's factory programmed Callendar-Van Dusen (CVD)
equation. This equation describes the relationship between resistance and temperature of
platinum resistance thermometers (RTDs). The matching process allows the user to enter the
four sensor specific Callendar-Van Dusen (CVD) constants into the transmitter. The transmitter
uses these sensor-specific constants in solving the CVD equation to match the transmitter to
that specific sensor thus providing outstanding accuracy. See comparison below:
Take away: “Transmitter-Sensor Matching customizes sensor curves to minimize sensor
inaccuracy”
Note
In order to use this diagnostic, the RTD must be set as type Cal VanDusen.
HART 7 Fast Keys
Sensor 1 - 2, 2, 1, 11
HART 7 Fast Keys
Sensor 1 - 2, 2, 2, 11
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
3144P ±0.08 °C 3144P ±0.08 °C
Standard RTD ±1.05 °C Matched RTD ±0.18 °C
Total System
(1)
(1) Calculated using root-summed-squared (RSS) statistical method.
±1.05 °C Total System
(1)
±0.21 °C
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
3144P ±0.08 °C 3144P ±0.08 °C
Standard RTD ±1.05 °C Matched RTD ±0.18 °C
Total System
(1)
(1) Calculated using root-summed-squared (RSS) statistical method.
±1.05 °C Total System
(1)
±0.21 °C