Kipp&Zonen UVS-E-T UV Radiometers - Manual (Page 15)

15
They are exposed to spectral irradiances between
280nm and 400nm (step increments 1 nm, slit width 2
nm at FWHM). The spectral measurements are
performed sequentially as the monochromator has one
exit slit only. Nevertheless, identical monochromator
output signals can be achieved for the photo-diode and
the UVS radiometer by positioning the sensitive
surfaces of both detectors at the same distance from
the exit slit.
A calibration factor is defined as the ratio between the
radiometer output and the radiation input, i.e. the
radiometer reading divided by the UV irradiance. To
obtain the radiometric calibration factor,
ρ, in the
laboratory, the UV radiometer output and the UV
irradiance input are determined using the
monochromatic measurements.
The broad-band UV radiometer output can be
calculated according to:
U
UVS
= u
UVS
(
λ
)
• d λ
∫
where u
UVS
(
λ
) are the spectrally measured test UVS
readings. u
UVS
(
λ
) is also referred to as the spectral
response function. The index UVS denotes the variable
of a broad-band UVS radiometer. The radiometer-
weighted UV irradiance input, can be calculated as:
E
UVS
=
e
Si
(
λ
)
• s
UVS
(
λ
)
• d λ
∫
A
eff
where e
Si
(
λ
) is the irradiance (in units of W/nm) of the
monochromator output (measured with the photo-
diode), s
UVS
(
λ
) is the normalized spectral response
function of the test UVS radiometer (i.e.
u
UVS
(
λ
)/max(u
UVS
(
λ
)), and A
eff
is the effective area (in
m
2
) of the UVS radiometer detection surface. Finally,
the radiometric calibration factor is obtained from the
two monochromator-based measurements (U
UVS
and
E
UVS
) according to
ρ=U
UVS
/E
UVS
. The units of
ρ are
V/(W/m2).