When measuring reflected apparent temperature (RTC), what emissivity should be set to?

• A. 1.0
• B. 0.1
• C. 0.5
• D. 0.95

Answer: (A)

RTC is about the temperature of the surroundings that are reflected off the surface. The infrared signal you detect is a mix of the object’s own emission and radiation reflected from the environment. Emissivity determines how much of that signal is attributed to emission versus reflection. To isolate and measure the reflected component reliably, you set the emissivity to the maximum value, 1.0. With this setting, the reading emphasizes the reflected ambient temperature, making the RTC value meaningful. Using lower emissivity would increase the influence of the object’s emission on the measurement, muddying the RTC reading and making it less accurate.