What emissivity setting should be used when measuring background/RTC in the example?

• A. Emissivity set to 1.0
• B. Emissivity set to 0
• C. Emissivity set to 0.5
• D. Emissivity set to 1.5

Answer: (A)

Emissivity controls how much of the infrared signal comes from the surface itself versus reflections from the surroundings. When measuring the background or using RTC, you want the reading to reflect the background’s emitted energy as if the surface were a perfect emitter. Setting emissivity to 1.0 achieves that, reducing influence from reflected ambient radiation and making the background temperature reading more accurate for RTC calibration. An emissivity of 0 would ignore the surface’s emission and be dominated by reflections, which isn’t appropriate here. A mid-range value like 0.5 would not align with the RTC background measurement, and 1.5 isn’t a physically valid emissivity. Therefore, 1.0 is the best setting.