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10
Test Probe Calibration
For optimum accuracy and stability, allow the calibrator to warm up for 10
minutes after power-up and then allow adequate stabilization time after reach-
ing the set-point temperature. After completing operation of the calibrator, al-
low the well to cool by setting the temperature to 150°C or less for one-half
hour before switching the power off.
10.1
Calibrating a Single Probe
Insert the probe to be calibrated into the well of the furnace calibrator. The
probe should fit snugly into the calibrator probe sleeve yet should not be so
tight that it cannot be easily removed. Avoid any dirt or grit that may cause the
probe to jam into the sleeve. Best results are obtained with the probe inserted to
the full depth of the well. Once the probe is inserted into the well, allow ade-
quate stabilization time to allow the test probe temperature to settle as de-
scribed above. Once the probe has settled to the temperature of the well, it may
be compared to the calibrator display temperature. The display temperature
should be stable to within 1°C degree for best results.
CAUTION: Never introduce any foreign material into the probe hole of
the insert. Fluids etc. can leak into the calibrator causing damage to the
calibrator or binding and damage to your probe.
10.2
Furnace Characteristics
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 furnace. However, actual heat losses will vary with design of
the thermometer probes inserted into the calibrator and the temperature. For
best results, insert probe to full depth of well.
CAUTION: Do not remove inserts and insulators at high temperatures.
Inserts and insulators are the same temperature as the display tempera-
ture. Use extreme care when removing hot inserts and insulators.
10.2.1
Stabilization and Accuracy
The stabilization time of the calibrator depends on the conditions and tempera-
tures involved. Typically the test well is stable to 0.5°C within 20 minutes of
reaching the set-point temperature as indicated by the display. Ultimate stability
is achieved 10 to 20 minutes after reaching the set temperature.
Inserting a cold probe into a well requires another period of stabilizing depend-
ing on the magnitude of the disturbance and the required accuracy. For exam-
ple, inserting a .25 inch diameter room temperature probe into a sleeve at
10 Test Probe Calibration
Calibrating a Single Probe
43
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