Optris' calibration service

A regular check up of your infrared pyrometers or thermal imagers helps preventing measuring mistakes and innaccurate measuring results.

The calibration and adjustment of our customers' devices takes place in our state-of-the-art in-house calibration laboratories. When issuing certificates, not only laboratory temperature and humidity are documented, but also the measurement distance and source diameter (calibration geometry).

Optris' own reference devices are inspected by the National Metrology Institute of Germany (Physikalisch Technische Bundesanstalt) once every year, assuring our customers that our temperature measuring devices provide the highly accurate and reliable measuring results, that are being necessary in quality control processes.

Since we are keen on our international distribution partners' continous training, we support them in setting up reginal calibration laboratories.

How does the calibration of IR temperature measuring devices work?

Infrared thermometers are calibrated with the help of reference radiation sources, so called black bodies. These radiation sources are able to produce different temperatures with a high stability.

Knowing the exact value of the radiation temperature is essential for the calibration process. It can be measuren by either using a contact thermometer or a transfer standard infrared thermometer. This calue can then be used to determine the device constant for an initial calibration of the infrared sensors. In order to conduct post-calibration by customers or local calibration facilities, the calibration temperature should be close to the temperatures which occur during the respective applications.

Optris uses the transfer standard radiation thermometer LS-PTB (see image) to measure the radiation temperature of a reference source. The LS-PTB is based on the portable IR thermometer optris LS. The LS-PTB must be traceable to the International Temperature Scale from 1900 (ITS-90). It is calibrated by the PTB (German National Metrological Institute) in regular intervals.

ITS-90 is a very good approximation of thermodynamic temperature. It is based on 17 well-reproducible fixed values such as melting points of highly purity metals. Within the scope of its ITS-90, the LS-PTB is compared to PTB national temperature standards within a closed chain of comparative measurements with known uncertainty. Based on the LS-PTB, Optris produces the LS-DCI as a high-precision reference IR thermometer for its customers. The DCI units are produces with pre-selected components which ensure high measurement stability. In combination with dedicated calibration at multiple calibration points, the LS-DCI scores a even higher accuracy than the series devices.

The optics of an IR thermometer is described by the distance-to-spot-ratio. Depending on the quality of the optics, a certain amount of radiation is also received from sources outside the specified measurement spot. The maximum value here equals the radiation emitted by a hemispheric radiant source. The respective signal chance in correlation with resizing the radiation source is described as the size-of-source effect (SSE). As a result of this correlation, all manufacturers of IR thermometers use accurately defined geometries for the calibration of their units; meaning depending on the aperture of the radiation source a distance between the IR thermometer and the reference source is defined. Thus, the calue specified in datasheets and technical documentation as measurement field is generally a specific defined percentage of the radiation maximum – values of 90 % or 95 % are common.

Do you prefer to take care of the calibration on your own? Using the calibration source optris BR 400, it is a piece of cake.