Fluke NetDAQ 2640A, Service Manual

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NetDAQ
Service Manual
1-24
2645A Four-Wire RTD per ITS-1990 Measurement Specifications 1-34.
Tables 1-37 and 1-38 provide 2645A 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. There is no two-wire RTD
capability for the 2645A.
Table 1-37. 2645A 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 specifications at 60
°
C is 0.75, then the
specification at 40
°
C =(.75-.2)x(40-28)/(60-28)+.2=.406.
Table 1-38. 2645A 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 0.03
°
C 0.06
°
C 0.16
°
C 0.25
°
C 0.25
°
C 0.62
°
C 1.10
°
C
0
°
C 0.03
°
C 0.06
°
C 0.20
°
C 0.31
°
C 0.31
°
C 0.85
°
C 1.30
°
C
100
°
C 0.03
°
C 0.06
°
C 0.23
°
C 0.34
°
C 0.34
°
C 0.95
°
C 1.40
°
C
300
°
C 0.03
°
C 0.06
°
C 0.30
°
C 0.41
°
C 0.41
°
C 1.18
°
C 1.70
°
C
600
°
C 0.03
°
C 0.06
°
C 0.53
°
C 0.63
°
C 0.63
°
C 1.62
°
C 2.12
°
C
2645A Thermocouple per ITS-1990 Measurement Specifications 1-35.
Tables 1-39 to 1-40 provide 2645A specifications for the thermocouple measurement
function per ITS-1990.
Table 1-39. 2645A Thermocouple General Specifications
Specification Characteristic
Input Impedance 100 M
Ω
minimum in parallel with 300 pF
Open Thermocouple Detect Operates by injecting a small ac signal into the input after each
measurement. A thermocouple resistance greater than 1 k to 10k is
detected as an open input.
Temperature Coefficient To calculate Thermocouple 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 0.6 and the specification at 60
°
C is 1.1, then the specification
at 40
°
C is =(1.1-0.6)x(40-28)/(60-28)+0.6=0.7875.