Emerson Rosemount X-well 648, Справочное руководство, Страница: 29 / 90

19
Reference Manual
00809-0200-4648, Rev BB
Configuration
July 2016
Configuration
2.8.2 Transmitter-sensor matching
Perform the transmitter-sensor matching procedure to enhance the temperature
measurement accuracy of the system (see the comparison below) 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 648 Wireless accepts Callendar-Van Dusen constants from a calibrated RTD
schedule and generates the actual curve to match that specific sensor curve.
1. The Actual Curve is identified from the Callendar-Van Dusen equation.
Total System Accuracy = ( Transmitter Accuracy)
2
+ (Sensor Accuracy)
2
Callendar-Van Dusen equation
R
t
= R
o
+ R
o

[t -

(0.01t-1)(0.01t) -

(0.01t - 1)(0.01t)
3
]
The following input variables, included with specially-ordered Rosemount temperature
sensors, are required:
R
o
= Resistance at Ice Point
Alpha = Sensor Specific Constant
Beta = Sensor Specific Constant
Delta = Sensor Specific Constant
Fast Key sequence
2, 1, 1
System accuracy comparison at 150 °C using a PT 100 (A=0.00385)
RTD with a span of 0 to 200 °C
Standard RTD Matched RTD
Rosemount 648 Wireless ±0.45 °C Rosemount 648 Wireless ±0.45 °C
Standard RTD ±1.05 °C Matched RTD ±0.018 °C
Total System
(1)
1. Calculated using root-summed-squared (RSS) statistical method.
±1.14 °C Total System
(1)
±0.048 °C
R
e
sistanc
e, O
h
m
Temperature,

C
Standard IEC 751
“Ideal” Curve
(1)
Actual Curve
0 °C