Computing R0 And Alpha; Calibration Example - Fluke 6050H User Manual

6050H
User's Guide

Computing R0 and ALPHA

Before computing the new values for R0 and ALPHA the current values must be
known. The values may be found by either accessing the probe calibration menu
from the controller panel or by inquiring through the digital interface. The user
should keep a record of these values in case they may need to be restored in the
future. The new values R0' and ALPHA' are computed by entering the old values
for R0 and ALPHA, the calibration temperature set-points t
temperature errors err
For example, if R0 and ALPHA were previously set for 100.000 and 0.0038500
respectively and the data for t
values R0' and ALPHA' would be computed as 100.193 and 0.0038272
respectively. Program the new values R0 and ALPHA into the controller. Check
the calibration by setting the temperature to t
again. If desired the calibration procedure may be repeated again to further
improve the accuracy.

Calibration Example

The bath is to be used between 75 and 125 °C and it is desired to calibrate the
bath as accurately as possible for operation within this range. The current values
for R0 and ALPHA are 100.000 and 0.0038500 respectively. The calibration
points are chosen to be 80.00 and 120.00 °C. The measured bath temperatures
are 79.843 and 119.914 °C respectively. Refer to Figure 9 for applying equations
to the example data and computing the new probe constants.
52
and err into the following equations:
L H
, t , err , and err
L H L
and t , and the
L H
were as given above, the new
H
and t and measuring the errors
L H