User manual

12-1
Chapter 12
Calibration Procedure
Note:
This procedure is to be considered a general guideline. Each
laboratory should write their own procedure based on their
equipment and their quality program. Each procedure should be
accompanied by an uncertainty analysis also based on the
laboratory’s equipment and environment.
Sometimes the user may want to calibrate the bath to improve the temperature
set-point accuracy. Calibration is done by adjusting the controller probe
calibration constants R0, ALPHA, and DELTA so that the temperature of the bath
as measured with a standard thermometer 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 bath. By using a good
thermometer and following this procedure the bath can be calibrated to an
accuracy of better than 0.5 °C up to 200 °C.
12.1 Calibration Points
In calibrating the bath, R0, ALPHA, and DELTA are to minimize the set-point
error at each of three different bath temperatures. Any three reasonably
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 Micro-Bath. The farther apart the calibration
temperatures, the larger will be the calibrated temperature range but the
calibration error will also be greater over the range. If for instance 50 °C to
150 °C is chosen as the calibration range then the calibrator may achieve an
accuracy of say ±0.3 °C over the range 50 to 150 °C. Choosing a range of 50 °C
to 90 °C may allow the calibrator to have a better accuracy of maybe ±0.2 °C
over that range but outside that range the accuracy may be only ±1.5 °C.