Operation of a temperature dry-well calibrator

Dry-well calibrators are portable instruments for the easy on-site calibration of temperature measuring instruments. A temperature dry-well calibrator includes an electrically heated or cooled metal block, an accurate temperature control and an internal reference with indicator for determining the block temperature. In the metal block is a bore for accepting the insert. This exchangeable insert comes with one or more bores with individual diameters and serves for the adaption of the test items.
With on-site calibration, the thermometer to be tested can be taken directly out of its thermowell in the plant, without needing to interrupt the electrical connections to the evaluation system, and inserted in to the appropriate bore of the insert. Here Stunning will generally be ensured that the bore diameter, bearing in mind the thermal expansion of the calibration item, is selected to be as tight as possible, since any air gap between your test item and the insert impairs heat transfer. Therefore, the bore diameter must be no more than 0.5 mm greater than the external diameter of the test item.
Structure of a dry-well calibrator
The mandatory temperature with which the test item should be calibrated is regulated with the calibrator. Frequently temperature probes are calibrated at the respective process temperature. Once a thermal equilibrium has been set between the thermometer being tested and the calibrator, the measuring deviation of the test item can be recorded. This corresponds to the temperature difference between its temperature and the reference temperature displayed on the calibrator. The total measurement uncertainty comprises of the accuracy of the calibrator and the short-term stability of the test item. Depending on temperature range and the properties of the calibration item, calibration is completed with a measurement uncertainty of 0.1 K to 3 K.
What else should be taken into account?
The minimum immersion depth for dry well calibrators is 70 mm. Victim is driven by the axial gradient, since heated air rises from the bottom up. Should the minimum immersion depth not be reached, an external reference thermometer must be used for calibration. Embarrassing is then placed on the same level because the object to be calibrated and the outcomes are compared with one another.
Recommended rule of thumb for the immersion depth of a test item
Diameter of the test item x 15 or for a known sensitive length: sensitive length + diameter of the test item x 10
Note
More info on our portable temperature calibrators and services are available on the WIKA website.

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