Fluke 2680A User Manual page 210

2680A/2686A
Users Manual
PAI Module Thermocouple per ITS-1990 Measurement Specifications
The following tables provide PAI Module specifications for the thermocouple
measurement function per ITS-1990.
Table A-18. PAI Module Thermocouple General Specifications
Input Impedance
Open Thermocouple Detect
Temperature Coefficient
Accuracy at -20 °C
A-14
Specification Characteristic
100 MΩ minimum in parallel with 300 pF
Operates by injecting a small ac signal into the
input after each measurement. A
thermocouple resistance greater than 1k to
10k is detected as an open input.
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 60v°C is
1.1, then the specification at 40v°C is =(1.1-
0.6)x(40-28)/(60-28)+0.6=0.7875.
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.