The detector’s
spectral response follows closely the erythema action spectrum
(Fig.1.)[1]. Due to built-in Teflon diffuser the detector has
negligible azimuthal error making the measurement insensitive to
the rotation of the detector. Extended measurement range of 600 MED/Hr enables measurement of intense radiation.
The detector’s spectral response follows closely the erythema
action spectrum (Fig.1.)[1]. Due to built-in Teflon diffuser the detector has negligible
azimuthal error making the measurement insensitive to the rotation of the detector.
Extended measurement range of 600 MED/Hr enables measurement of intense radiation.
In conjunction with the Solar Simulator and XPS200 Xenon Lamp Power Supply the PMA2100
with the PMA2103 detector can operate as a smart dose controller/monitor substantially
enhancing the functionality of the Solar Simulator.
The measurement result can be shown in MED/Hr, µW/cm2 as
well as a time to accumulate 1 MED. The detector's high dynamic range allows measurements
down to 0.1 µW/cm2 with the ability to measure radiation as strong as 3.5
mW/cm2.
The biologic effectiveness of ultraviolet radiation is strongest for
wavelengths between 280 to 320 nm, classified as UV-B by the CIE. Several biologic action
spectra, functions relating wavelength and the biologic effectiveness, are shown in Figure
3. The most commonly used, erythema action spectrum [1], also referred to as CIE 1987
action spectrum, represents the sensitivity of human skin to sunburn.
Other biologic action spectra also exhibit rapid decline in UV effect with an increase
of wavelength over the UV-B range. In general the reading of an erythemally weighted
detector cannot be directly interpreted as biological effectiveness other than erythemal.
However, there are ways to make the necessary correction numerically [2].
The biologic effectiveness of the UV radiation can be measured in terms
of effective irradiance in radiometric units, for example [µW/cm2]. It is
often related to the sensitivity of the human skin to sunburn and expressed in Minimal
Erythemal Doses per Hour [MED/Hr]. One MED/Hr is the effective irradiance capable of
causing minimum redness (erythema) in an average number 2 skin. Based on a study [3], the
relationship between MED/Hr and radiometric units was determined to be:
1 [MED/Hr] = 5.83 [µW/cm2]
This formula is programmed into the PMA2103 detector allowing for easy
conversion of units. Consequently, the integrated effective dose can be expressed in
[mJoules/cm2] or MED.
Many sources produce UV radiation with a spectral irradiance changing
rapidly over narrow wavelengths range. Spectral irradiance of the solar UV (Fig. 4) is an
extreme example of such steep slope due to the UV-B and UV-C absorbing ozone layer.
