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8 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
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ing the set-point temperature. After completing the test probe calibration proce
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dure, allow the well to cool by setting the temperature to 25°C for one-half
hour before switching the power off. Actual use of this instrument should be
determined by your applicable Quality Assurance requirements. The following
procedure is provided for information only.
8.1 Calibrating a Single Probe
Insert the probe to be calibrated into the test well of the instrument. The probe
should fit snugly into the calibrator test well 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 test well. Best results are obtained with the probe inserted to the
full depth of the test well. Once the probe is inserted into the test well, allow
adequate stabilization time to allow the test probe temperature to settle as de-
scribed above. Once the probe has settled to the temperature of the test well, it
may be compared to the calibrator display temperature.
CAUTION: Never allow foreign material into the probe holes of the
block. Fluids and other materials can damage the instrument causing
binding and damage to your probe.
8.2 Dry-well 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 dry-well. However, actual heat losses vary with design of the
thermometer probes inserted into the calibrator and the temperature. For best
results, insert probe to full depth of test well.
8.2.1 Stabilization and Accuracy
The stabilization time of the instrument depends on the conditions and temper
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atures involved. The well requires considerable time to reach the set-point de
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pending on the span. Additional time is required to stabilize within ±0.1°C of
the set-point.
Inserting a cold probe into a test well requires another period of stabilizing de
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pending on the magnitude of the disturbance and the required accuracy. For ex
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ample, inserting a 0.25 inch diameter room temperature probe into a test well at
300°C takes 5 minutes to be within 0.1°C of its settled point and takes 10 min
-
utes to achieve maximum stability.
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8 Test Probe Calibration
Calibrating a Single Probe