Upgradation of a spectral irradiance measurement facility at National Physical Laboratory, India

Abstract

This report describes the details of a recently upgraded spectral irradiance measurement facility in optical radiation standards at National Physical Laboratory, India. This facility provides the calibration of spectral irradiance in the wavelength range 280 nm -2500 nm. PTB, Braunschweig, Germany calibrated five numbers of 1000 W quartz halogen lamps, which are used as reference standards for spectral irradiance scale. In addition to providing the details of instruments, the procedure of calibration and evaluation of uncertainties is also described. For checking the fidelity, repeatability and reproducibility of the upgraded system, calibration of one of the PTB calibrated lamps, was done against the other four PTB calibrated lamps. These measurements not only provide confidence on the upgraded system but also verify the retention of the PTB certificate values after a lapse of two years after their calibration.

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

“…The generated electrical signal is proportional to the radiant flux incident on the detector surface. This radiant flux falling on surface of unit area is called irradiance in the context of radiometry [ 17 , 18 ]. Thus, a detector signal is directly proportional to irradiance [ 19 ].…”