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Portable temperature calibrators

Efficient calibration with temperature calibrators from WIKA

Portable temperature calibrators (dry-well calibrators) are electronic controllers which automatically, quickly and dryly supply a temperature. Due to the high reliability, accuracy and simple operation, portable temperature calibrators are particularly suitable as a factory/working standard for the automatic testing and/or calibration of temperature measuring instruments of all types. A major advantage is offered by the large sleeve diameters and the fast, stable temperature control, since, as a result of these characteristics, the time for calibration can be used very effectively.
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What is a dry-well calibrator?

Portable dry-well calibrators, also known as temperature calibrators or dry blocks, are used for the accurate and reliable checking and calibration of temperature measuring instruments on site. Dry-well calibrators are essential for ensuring that temperature sensors provide accurate and consistent measured values over time.

How is a portable temperature calibrator constructed?

A portable temperature dry-well calibrator consists of a temperature-controlled metal block that is electrically heated or cooled. The metal blocks are interchangeable and available with different bores. The bores correspond to the individual diameters of the test items and their inserts. A dry-well calibrator should have at least one hole for the reference instrument and one hole for the thermometer being calibrated. The bores must have a certain fit with the inserts, which means that different inserts are necessary for the different temperature probes, so calibrators with interchangeable inserts are recommended. The calibrator regulates the required temperature at which the test item must be calibrated.

How do temperature calibrators work?

Temperature calibration takes place by measuring temperature points within the temperature range of the probe. These measurement results are then compared with a reference instrument or defined fixed points. For calibration, the test item is inserted firmly into the calibration insert. The clearance between the temperature probe and the insert must only be a few millimetres, as the ambient air can falsify the measured values and thus the calibration results. The inserts are then used to adjust the probe to the desired temperature in the block and thus calibrate it.

What are dry-well calibrators used for?

Portable dry-well calibrators are often used as the preferred calibration method, since the user is spared the need to handle liquid. Particularly sterile industries, such as the pharmaceutical industry or the food industry, use dry-well calibrators to calibrate their temperature measuring instruments. The probes do not come into contact with other substances that are harmful to the end product. Other areas of application include the chemical industries, iron and steel industries and also the traditional calibration laboratory.

What is the minimum immersion depth with dry-well calibrators?

For dry-well calibrators, the minimum immersion depth is 70 mm. If the minimum immersion depth is not reached, an external reference instrument, which is brought to the same height as the thermometer, must be used for calibration. To find out the appropriate immersion depth of a test item, the following rule of thumb can be applied:

Diameter of the test item x 15 or for a known sensitive length: sensitive length + diameter of the test item x 10.

What material are the inserts for a dry-well calibrator made from?

Depending on the diameter of the temperature sensor, an appropriate immersion sleeve is required for each temperature probe. In addition to the diameter, the material of which the insert is made is also a selection criterion. For extremely high temperatures, sleeves made of ceramic are recommended, whereas the most-common inserts are made of brass or aluminium.

FAQ
FAQ

For the insert of a dry well calibrator, how large should the bore diameter be?

The diameter of a test item determines the size of the drilled bore. The bore diameter should be as small as possible after taking into account the thermal expansion of the test item. This is because the air gap between the thermometer and the bore ...

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In temperature calibration, what is an axial gradient?

An axial gradient is the temperature difference, or temperature gradient, from the bottom (maximum immersion depth) to the top (surface of the calibrator).