• The Reference Spectrophotometer developed at NMC is the reference standard for the spectral transmittance measurement. Spectral transmittance is a basic quantity in spectrophotometry.


• The Reference Spectrophotometer is a single beam geometry instrument. The collimation of the parallel beam is 0.013 radian and the solid angle of collection of the detector system is 0.004 steradian. The fully characterised reference spectrophotometer establishes the national scale of spectral regular transmittance over the wavelength range of 350 nm to 1100 nm. Its measurement uncertainty is estimated to be 0.000052 transmittance units (0.052 % relative) for neutral density filters with nominal transmittance of 0.1 transmittance units.

Reference spectrophotometer

Schematic diagram of reference spectrophotometer