Theoretical Simulation for Evaluating Error in Irradiance Measurement Using Optical Detectors Having Different Cosine Responses

Cosine response is an important characteristic of an optical detector for irradiance measurements. The non-ideal cosine response of a detector may lead to errors in irradiance measurements. In this paper, a theoretical simulation of irradiance generated due to isotropic point light sources is carried out for different illumination conditions. Simulation results show that the errors in irradiance measurements due to the cosine error of detectors become significantly high at the edges and corners of the floor when a light source is placed at the center of the roof. Further, it is observed that the errors are more in the enclosures having a height smaller than the floor dimensions. Even calibrated detectors measure erratic values of irradiance for a wider angle of incidence. Therefore, cosine errors in irradiance measurements are of great importance especially during the current scenarios of the COVID-19 pandemic, for ensuring the correct dose of Ultraviolet Germicidal Irradiation (UVGI).