4.3 Calibration
The enclosure should be set and operated at the specified temperature and allowed to
reach steady state conditions before proceeding to the next step of measurement
recording.
The temperature readings of the chamber and of all standard sensors should be
recorded simultaneously. The recording interval shall commence after steady state
has been achieved and shall be a sufficient period of time to characterize or
determine the stability. A graphical record is preferable.
To confirm the enclosure performance and usage temperature range, a check of an
enclosure at a single temperature is not recommended. These guidelines recommend
that the chambers be calibrated at a minimum of two different temperatures. A single
temperature check may be performed if specified by the customer, or if other
technically valid reasons can be demonstrated.
4.4 Investigation of Enclosure Performance
a) The temperature uniformity and stability shall be calculated as in the definition.
As part of the calibration for discrete points of the chamber according to specific
checks, only uncertainty contributions based on the variation can be determined.
b) The raw data of indicating device and each sensor reading should be averaged.
The correction of standard might be added individually for better accuracy;
otherwise a component of uncertainty should be included in the uncertainty
budget for uncorrected errors. The calculation data should be reported.
c) An example of the enclosure calibration and data recording using 9 sensors at a
setting of 50 °C is shown below.