Emissivity is a gain adjustment to compensate for the loss of the IR energy being emitted from the target material’s surface. Use a contact thermocouple and aim the Pyrometer at an adjacent spot (very close to the thermocouple) and adjust the emissivity of the sensor or thermal imaging camera to match the thermocouple temperature reading.
An Emissivity of 1.00 is 100% of incoming IR energy. Nothing in life has 100% IR energy emission. The closest is a blackbody calibration source that can produce and provide a constant IR energy output of approximately 0.998.
The emissivity is determined by the internal cavity shape of the blackbody source. A spherical cavity with a small aperture opening offers the highest emissivity. Other cavity designs which offer high emissivity are cylindrical and conical designs. When more internal reflections are contained within a cavity, the higher the IR emissivity emission.
When lowering the IR sensing devices emissivity down from 1.00 to 0.50, the output signal / temperature reading of the IR sensing device increases.