For the most accurate IR temperature reading of a surface, which combination should the surface have?

• A. Low emissivity and low reflectivity
• B. High emissivity and low reflectivity
• C. High reflectivity and high emissivity
• D. Low emissivity and high reflectivity

Answer: (B)

When you measure surface temperature with an infrared tool, you want the surface to behave like a good emitter and not reflect a lot of ambient infrared energy. Emissivity is how efficiently a surface emits infrared radiation compared to a perfect emitter; high emissivity means most of what the sensor detects comes from the surface itself. Reflectivity is how much ambient infrared radiation is reflected off the surface into the sensor; low reflectivity means less stray radiation from surroundings contaminating the reading. So the best scenario is a surface that emits infrared well (high emissivity) and reflects little ambient energy (low reflectivity). This makes the sensor’s reading closely correspond to the actual surface temperature. Surfaces that are shiny or metal often have low emissivity and high reflectivity, which can skew readings, while matte, non-metallic surfaces with high emissivity yield more accurate results.