Table of Contents
Advertisement
Thermocouple Calibration Procedure
Figure B-1: Type E Thermocouple Calibration Setup
3.
Mechanically fix the hot junction of the thermocouple under test at the midpoint of
the sensing portion of the PRT using a suitable nonconductive tie. Ensure that any
bare thermocouple wires do not touch the PRT sheath.
4.
Place the PRT and the attached thermocouple hot junction in the stirred bath and
allow it to stabilize.
5.
Record the PRT resistance using the digital multimeter. Convert to temperature using
calibration constants for the PRT or by linear interpolation if temperature tables are
available for the PRT.
6.
Using the polynomial equations from NIST Monograph 175 for the appropriate
thermocouple type, determine the expected output voltage the thermocouple at the
PRT temperature.
7.
Record the output voltage of the thermocouple using the digital multimeter.
8.
Subtract the voltage determined in Step 6 from the voltage recorded in Step 7. This is
the error for this thermocouple at 26°C. Affix a tag to the thermocouple stating the
error. Be sure to include the polarity of the error.
9.
After calibration, cut off the welded or soldered hot junction of the thermocouple (do
not cut the copper connections from the thermoelements). The part cut off should be
minimal so that the composition or portion of the thermoelements available for future
use is as close as possible to the composition of the thermoelements that made up the
hot junction.
B-2
Advertisement
Table of Contents
