Calibration Procedure; Calibration Points - Fluke 9150 User Manual

At times the user may want to calibrate the unit to improve the temperature set-
point accuracy. Calibration is done by adjusting the controller probe calibration
constants CE1, CE2, and CE3 so that the temperature of the unit as measured
with a standard thermocouple agrees more closely with the set-point. The
thermometer used must be able to measure the well temperature with higher
accuracy than the desired accuracy of the unit.

11.1 Calibration Points

In calibrating the unit, CE1, CE2, and CE3 are adjusted to minimize the set-point
error at each of three different well temperatures. Any three reason- ably
separated temperatures may be used for the calibration. Improved results can be
obtained for shorter ranges when using temperatures that are just within the most
useful operating range of the unit. The farther apart the calibration temperatures,
the larger the calibration range but the calibration error is also greater over the
range. Choosing a range of 150°C to 500°C may allow the calibrator to have a
better accuracy of maybe ±2.0°C but outside that range the ac- curacy may be
greater than ±10.0°C.

11.2 Calibration Procedure

1. Choose three set-points to use in the calibration of CE1, CE2, and CE3
2. If the normal set-points are not used, initialize CT1, CT2, and CT3 to the
3. Set the unit to the low set-point. When the unit reaches the set-point and the
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parameters. These set-points are generally CT1 = 150°C, CT2 = 675°C and
CT3 = 1200°C but other set-points may be used if desired or necessary.
Using these three temperature set-points may result in ±4.0°C accuracy.
desired set points. Where CT1 is the low-set point and CT3 is the high set-
point.
display is stable, wait 15 minutes or so and take a reading from the
thermometer. Repeat step 3 for the other two set-points recording them as
Tm1, Tm2, and Tm3.
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