A-35. 2645A Thermocouple General Specifications; A-36. 2645A Thermocouple Specifications - Fluke NetDAQ 2640A User Manual

2645A Thermocouple per ITS-1990 Measurement Specifications A-27.
Tables A-35 to A-36 provide 2645A specifications for the thermocouple
measurement function per ITS-1990.
Table A-35. 2645A Thermocouple General Specifications
Specification
Input Impedance
Open Thermocouple Detect
Temperature Coefficient
Accuracy at -20 C
Thermocouple
Type Temperature ºC
J -100 to 80
80 to 230
230 to 760
K -100 to -25
-25 to 120
120 to 1000
1000 to 1372
N -100 to -25
-25 to 120
120 to 1000
1000 to 1300
Table A-36. 2645A Thermocouple Specifications
Resolution
.3
.2
.2
.4
.3
.3
.3
.5
.5
.4
.3
Characteristic
100 M minimum in parallel with 150 pF
Operates by injecting a small ac signal into the
input after each measurement. A thermocouple
resistance greater than 1 k
detected as an open input.
To calculate Thermocouple accuracy for
temperatures between 28ºC and 60ºC, or -10ºC
and 18ºC, use a linear interpolation between
the two applicable points. e.g., if the applicable
spec at 28ºC is .6 and the spec at 60ºC is 1.1,
then the spec at 40ºC is (1.1-.6)*(40-28)/(60-
28)+.6 = .5*(12.32) + .6 = .7875.
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.
Accuracy
18ºC to 28ºC
90 1 Year
Day
Slow Slow Fast
0.8 0.9 1.6
0.7 0.8 1.4
0.7 0.8 1.3
1.0 1.1 2.0
0.8 0.9 1.7
0.9 1.1 1.8
1.2 1.5 2.3
1.4 1.5 2.8
1.1 1.3 2.3
1.0 1.1 2.0
1.0 1.2 1.9
Specifications
2645A Specifications
to 10 k is
ºC
-10ºC to 60ºC
1 Year
Slow Fast
0.9 1.7
0.9 1.5
1.0 1.5
1.2 2.1
1.0 1.8
1.5 2.2
2.0 2.9
1.5 2.9
1.3 2.4
1.2 2.1
1.6 2.4
A-23
A