©
National Instruments Corporation
13
USB-9211/9211A User Guide and Specifications
Figure 12.
Type K Errors
Figure 13.
Type R and S Errors
Cold-Junction Temperature Measurement Accuracy
Heat from other nearby heat sources can cause errors in thermocouple
measurements by heating up the terminals so that they are at a different
temperature than the cold-junction compensation sensor used to measure
the cold junction. The thermal gradient generated across the terminals can
cause the terminals of different channels to be at different temperatures, so
the resulting measurement creates errors not only in absolute accuracy but
also in the relative accuracy between channels.
–200
0
200
400
600
800
1000
1200
0
1
2
3
4
Max over Temp Range with Autozero
Max at Room Temp Range without Autozero
Typ over Temp Range with Autozero
Error (
°
C)
Measured Temperature (
°
C)
–200
0
200
400
600
800
1000
1200
0
2
4
6
Max over Temp Range with Autozero
Max at Room Temp Range without Autozero
Typ over Temp Range with Autozero
Error (
°
C)
1400
1600
Measured Temperature (
°
C)
