A Comparison of Radiometric and Spectrometric Emissivity Evaluation Methods in Infrared Thermometry

Area of Science:

• Physics
• Materials Science
• Metrology

Background:

• Accurate radiation thermometry relies on surface emissivity, which is often unknown and variable.
• Theoretical models for spectral emissivity exist but lack practical validation under application-relevant conditions.

Purpose of the Study:

• To compare spectral and radiometric emissivity evaluation methods on metallic samples up to 350 °C.
• To assess the practical validity of spectral emissivity evaluation against radiometric measurements.

Main Methods:

• Spectral emissivity evaluation using spectroscopy-measured data and instrument sensitivity.
• Radiometric emissivity evaluation using radiation thermometer radiance measurements and reference contact temperature.
• Comparison of methods on chromium nitride (CrN)-coated, raw metal, and polysiloxane-coated samples.

Main Results:

• Good agreement between spectral and radiometric methods observed for stable, homogeneous CrN-coated samples.
• Practical limitations identified for raw metals and polysiloxane-coated samples due to surface instability and inhomogeneity.
• Spectral emissivity evaluation confirmed as valid when underlying assumptions are met.

Conclusions:

• Spectral emissivity evaluation is practically valid under specific conditions, aligning with theoretical expectations.
• Radiometric evaluation remains the preferred method for in situ infrared thermometry applications.
• Surface condition significantly impacts the accuracy and agreement of emissivity evaluation methods.