Influence of atmosphere on calibration of radiation thermometers

Mlačnik, Vid (author), Pušnik, Igor (author)

Current process of calibrating radiation thermometers, including thermal imagers, relies on measurement comparison with the temperature of a black body at a set distance. Over time, errors have been detected in calibrations of some radiation thermometers, which were correlated with moisture levels. In this study, effects of atmospheric air on thermal transmission were evaluated by the means of simulations using best available resources of the corresponding datasets. Sources of spectral transmissivity of air were listed, and transmissivity data was obtained from the HITRAN molecular absorption database. Transmissivity data of molecular species was compiled for usual atmospheric composition, including naturally occurring isotopologs. Final influence of spectral transmissivity was evaluated for spectral sensitivities of radiation thermometers in use, and total transmissivity and expected errors were presented for variable humidity and measured temperature. Results reveal that spectral range of measurements greatly influences susceptibility of instruments to atmospheric interference. In particular, great influence on measurements is evident for the high-temperature radiation pyrometer in the spectral range of 2–2.7 µm, which is in use in our laboratory as a traceable reference for high-temperature calibrations. Regarding the calibration process, a requirement arose for matching the humidity parameters during the temperature reference transfer to the lower tiers in the chain of traceability. Narrowing of the permitted range of humidity during the calibration, monitoring, and listing of atmospheric parameters in calibration certificates is necessary, for at least this thermometer and possibly for other thermometers as well.

• Language: English
• Keywords: transmissivity of air, radiation thermometer, calibration, measurement errors, measurement uncertainty, moisture, humidity, infrared thermometers
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FE - Faculty of Electrical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2021
• Number of pages: 13 str.
• Numbering: Vol. 21, iss. 16, art. 5509
• PID: 20.500.12556/RUL-136093
• UDC: 621.317:536.51
• ISSN on article: 1424-8220
• DOI: 10.3390/s21165509
• COBISS.SI-ID: 74176771
• Publication date in RUL: 12.04.2022

Record is a part of a journal

• Title: Sensors
• Shortened title: Sensors
• Publisher: MDPI
• ISSN: 1424-8220
• COBISS.SI-ID: 10176278

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.
• Licensing start date: 16.08.2021

Secondary language

• Language: Slovenian
• Keywords: transmisivnost zraka, sevalni termometri, kalibracija, merilne napake, merilna negotovost, zračna vlaga, infrardeči termometri

Projects

• Funder: ARRS - Slovenian Research Agency
• Project number: P2-0225
• Name: Metrologija in kakovost

• Funder: Other - Other funder or multiple funders
• Funding programme: Republic of Slovenia, Ministry of Economic Development and Technology, Metrology Institute
• Project number: 6401-18/2008/70