Knowing the exact value of the radiation temperature is essential for the calibration process. It can be measured by either using a contact thermometer (in combination with the determination of the emissivity) or a transfer standard infrared thermometer. This value can then be used to determine the device constant for an initial calibration of the infrared sensors. In order to conduct a post-calibration by customers or local calibration facilities, the calibration temperature should be near the temperatures which occur at the respective applications.
Optris makes use of a transfer standard radiation thermometer CTlaser-PTB (see figure) to measure the radiation temperature of a reference source. The CTlaser- PTB is based on the IR thermometer optris CTlaser. The CTlaser-PTB needs to be traceable to the international temperature scale from 1990 (ITS-90). Thus, it is calibrated by the PTB (German national metrology institute) on a regular basis. 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 pure metals. Within the framework of ITS-90 the CTlaser-PTB is compared to national temperature standards from the PTB. This comparison within a closed chain of comparative measurements with a known uncertainty in measurement takes place on a regular basis.
Based on the CTlaser-PTB, Optris produces the CTlaser- DCI as a high-precision reference IR thermometer for its customers. The DCI units are produced with pre-selected components supporting high stability of measurement. In combination with a dedicated calibration at several calibration points the CTlaser-DCI achieves a higher accuracy than units from series production.
The optics of an IR thermometer is described by the distance-to-spot-ratio (D:S). 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 change in correlation with a resize of the radiation source is described by 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) a distance (a) between the IR thermometer and the reference source is defined. Thus, the value specified in datasheets and technical documentation as a measurement field is, in general, a certain defined percentage of this radiation maximum – values of 90 % or 95 % are common.
The newly developed optris Xi 80 combines the benefits of infrared cameras and infrared thermometers.
A full 80x80 thermal image eliminates the hunt for the hot spot and tedious positioning required with single spot temperature sensors. The integrated spot finder function will identify the hottest (or coldest) spot in the image and automatically communicate these measurements without an external PC.
A wide range of optics including the new 80° lens equips the Xi 80 to collect and analyze temperature information over a wide target area. The affordable pricing for this unit makes it a realistic alternative to replace existing spot temperature sensors or for OEM applications.
The newly developed optris Xi 400 combines the benefits of a robust, compact pyrometer and an advanced IR camera. The 80 Hz frame rate allows for the monitoring of fast thermal processes, even including a line-scan function. The spot finder IR camera has an optical resolution of 382 x 288 pixels and comes with an extensive ready-to-use package - including a versatile image processing software.
Due to its compact design and an affordable pricing, the new optris Xi spot finder IR camera is ideally suited for OEM applications.
The infrared cameras optris PI 400i / PI 450i are the smallest thermographic cameras in their class. Being equipped with a measurement speed of 80 Hz and an optical resolution of 382 x 288 pixels they provide real-time thermographic images in high speed.
The IR camera PI 450i is, due to its thermal sensitivity of 40 mK, specifically suited for the detection of slightest temperature differences, making it indispensable in quality control of products and in medical prevention.
The compact and high-performance infrared cameras offer a temperature range of -20°C up to 900°C, being optionally upgradeable up to 1500 °C. They can be delivered with exchangeable optics, industrial thermal imager equipment and they come with an extensive license-free thermography software package.