Fluke NetDAQ 2640A, Service Manual

Page: 33 / 260

Introduction and Specification
Specifications
1
1-17
2640A Four-Wire RTD per ITS-1990 Measurement Specifications 1-25.
Tables 1-22 and 1-23 provide 2640A specifications for the four-wire Resistance-
Temperature Detector (RTD) measurement function. The four-wire measurements use 2
input channels a decade apart, e.g., channels 4 and 14.
Table 1-22. 2640A Four-Wire RTD Temperature Coefficient
Specification Characteristic
Temperature Coefficient 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.
Table 1-23. 2640A Four-Wire RTD Specifications
Accuracy, 3
σ
Temperature
Resolution 90 Day
18
°
C to 28
°
C
1 Year
18
°
C to 28
°
C
1 Year
-10
°
C to 60
°
C
Slow Fast Slow Fast Slow Slow Fast
-200
°
C 0.003
°
C 0.007
°
C 0.06
°
C 0.16
°
C 0.09
°
C 0.33
°
C 0.63
°
C
0
°
C 0.003
°
C 0.007
°
C 0.09
°
C 0.20
°
C 0.13
°
C 0.53
°
C 0.86
°
C
100
°
C 0.003
°
C 0.007
°
C 0.10
°
C 0.23
°
C 0.16
°
C 0.63
°
C 0.97
°
C
300
°
C 0.003
°
C 0.007
°
C 0.14
°
C 0.30
°
C 0.21
°
C 0.83
°
C 1.20
°
C
600
°
C 0.003
°
C 0.007
°
C 0.19
°
C 0.53
°
C 0.30
°
C 1.20
°
C 1.60
°
C
2640A Two-Wire RTD per ITS-1990 Measurement Specifications 1-26.
The 2640A 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-ohm (approximately 13
°
C) positive offset. This value varies
for each channel and temperature gradient (n1%/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.