Fluke 2680A User Manual page 209

PAI Module 4-Wire RTD per ITS-1990 Measurement Specifications
The following tables provide PAI Module specifications for the 4-wire Resistance-
Temperature Detector (RTD) measurement function. The 4-wire measurements
use 2 input channels a decade apart, e.g., channels 4 and 14.
Table A-16. PAI Module 4-Wire RTD Temperature Coefficient
Specification
Temperature Coefficient
Accuracy at -20 °C
Resolution
Temperature
Slow
-200 °C 0.003 °C
0 °C 0.003 °C
100 °C 0.003 °C
300 °C 0.003 °C
600 °C 0.003 °C
PAI Module 2-Wire RTD per ITS-1990 Measurement Specifications
The PAI Module specifications for the two-wire Resistance Temperature Detector
(RTD) measurement function is based on the four-wire RTD measurement
specification (above) except you add a nominal 5 Ω (approximately 13 °C)
positive offset. This value varies for each channel and temperature gradient
(nominal +1%/ºC). Also note that the resistance of the RTD wiring adds directly to
the error. After 100 million operations of a measurement channel, the offset will
increase at an indeterminate rate.
To calculate RTD accuracy for temperatures between 28 °C
and 60 °C, or -10 °C and 18 °C, use a linear interpolation
between the two applicable points. For example, if the
applicable specification at 28 °C is 0.2 and the specification at
60 °C is 0.75, then the specification at 40 °C is =(.75-.2)x(40-
28)/(60-28)+.2=0.406.
Multiply the -10 °C to +60 °C accuracy specification by 2. After
1 hour warm-up. For accuracy between -10 °C and -20 °C,
interpolate linearly.
Table A-17. PAI Module 4-Wire RTD Specifications
18 °C to 28 °C
Fast Slow
0.007 °C 0.06 °C
0.007 °C 0.09 °C
0.007 °C 0.10 °C
0.007 °C 0.14 °C
0.007 °C 0.19 °C
Characteristic
Accuracy, 3σ
90 Day 1 Year
18 °C to 28 °C
Fast Slow
0.16 °C 0.09 °C
0.20 °C 0.13 °C
0.23 °C 0.16 °C
0.30 °C 0.21 °C
0.53 °C 0.30 °C
Appendices
A
Specifications
1 Year
-10 °C to 60 °C
Slow Fast
0.33 °C 0.63 °C
0.53 °C 0.86 °C
0.63 °C 0.97 °C
0.83 °C 1.20 °C
1.20 °C 1.60 °C
A-13