2680A/2686A
Users Manual
A-14
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
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 1k 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 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.
Accuracy at -20
°
C
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.
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