Based on a grating double-monochromator

a high-precision

automated and single-beam spectral radiometer was designed for the high-accuracy measurement of ultralow spectral transmissivity of ultraviolet filter. It mainly consists of a xenon arc lamp with high stabilization

a one-aperture screen with shutter

quartz lenses

a neutral density degradation plate

an ultraviolet grating double-monochromator

a photodetector and an electronic control system

and the spectral transmissivity is 10

-6

~10

-8

in spectral ranges from 200 nm to 400 nm. Measurement process can be controlled by a computer with special software. The principle

measurement method and datum processing method of the instrument were provided

and measurement uncertainty was analyzed. A filter sample was measured with this instrument

the measured results demonstrate that the spectral instrument has high precision

fast speed

and the measurement combined standard uncertainty is less than 3.16×10

-3

which meets the requirements of measurement precision. This instrument can be used to measure the spectral transmissivity of ultraviolet filter with high precision requirement.