Is a thermocouple suitable for measuring background or RTC according to the material?

• A. Yes
• B. No
• C. Only with a calibration
• D. Only at room temperature

Answer: (B)

Thermocouples are contact temperature sensors that read the actual temperature at the point where the probe touches. In infrared measurements, the background or RTC refers to the temperature information carried by the radiant energy the camera detects, which is a radiometric (radiant) temperature, not the surface temperature at a contact point. Because a thermocouple measures heat by conduction at its tip, it cannot reliably represent the radiant background seen by the camera. Calibrating a thermocouple won’t change what it measures, since it’s measuring contact temperature, not radiance. The right approach for background or RTC references is a non-contact, radiometric reference, not a thermocouple. So it is not suitable.