Fluke 9107 - Manual (Page 57)

10.2.1 Vertical Gradient
There is a temperature gradient vertically in the test well. The heater has been
applied to the block in such a way as to compensate for nominal heat losses out
of the top of the dry-well and minimize vertical temperature gradients. How-
ever, actual heat losses will vary depending on the number and types of probes
inserted into the calibrator and the block temperature. For best results, insert
probes the full depth of well.
10.2.2 Stabilization and Accuracy
The stabilization time of the dry-well calibrator will depend on the conditions
and temperatures involved. Typically, the dry-well will be stable to 0.1°C
within 5 minutes of reaching the set-point temperature as indicated by the dis-
play. Ultimate stability will be achieved 10 to 20 minutes after reaching the set
temperature.
Inserting a cold probe into a well will require another period of stabilization de-
pending on the magnitude of the disturbance and the required accuracy. For ex-
ample, inserting a ¼ inch diameter room probe at temperature into a sleeve at
300°C will take approximately 5 minutes to be within 0.1°C of its set-point and
will take 10 minutes to achieve maximum stability.
Decreasing the time required for the calibration process can be accomplished
by knowing how soon to make the measurement. It is recommended that typi-
cal measurements be made at the desired temperatures with the desired test
probes to establish these times.
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10 Test Probe Calibration