What is Emissivity?

The material emissivity (written as “ε” or “e”) is the relative power of its surface to emit heat by radiation. Materials are assigned an emissivity value between 0 and 1.0. Emissivity is a measure of a material’s ability to emit infrared energy. The emissivity of a surface is the ratio of the energy radiated from it to that from a blackbody at the same temperature, the same wavelength and under the same viewing conditions.

The Importance of Emissivity in Electrical Thermography 

Manufacturing facilities are full of equipment requiring periodic infrared (IR) inspection. The goal is to obtain an accurate assessment of equipment health. The most critical part of the assessment is properly compensating for the various emissivity values of all the components measured. Slight errors in emissivity compensation can lead to significant errors in temperature and ΔT (difference in temperature) calculations. Electrical cabinets are a good example, as they may contain materials with emissivity values ranging from 0.07 to 0.95.