UVB DETECTOR
Data and application notes


PURPOSE

The SolData UVB detector is designed to measure ultraviolet radiation in the critical 280-315 nanometer (nm) spectral range. This type of radiation is particularly important in the evaluation of the risk of sunburn, skin cancer and eye injury. The UVB irradiance at the surface of the earth is also dependent on the thickness of the ozone layer.


DESCRIPTION

SPECTRAL RESPONSIVITY

The spectral responsivity of the instrument closely follows the CIE erythemal response curve shown at the right (CIE JG 17-22, 1987). The graph shows how human skin sensitivity to erythema (reddening/burning) varies with wavelength. The same response curve is believed to describe the skin response leading to skin cancer. The unit MED (minimum erythemal dose) is the minimum UVB exposure which will cause a detectable reddening of the skin for an average person. This corresponds to a total dose of 210 J/m2.


CIE Erythemal response to UV radiation.

The SolData UVB detector uses a SiC photodiode with CIE 87 response.

In the tropics UVB exposure can be extremely high. Skin protection here is essential.

TECHNICAL SPECIFICATIONS
Mass:100 gram
Diameter:59 mm
Height:52 mm
Cable:120 cm, 5 pole DIN
Detector:SiC photodiode
Spectral response:CIE 87
Spatial response:Cosine
Supply voltage:5-12 V DC (< 1 mA)
Output voltage:1 volt/6 UVI

NB: 1 UVI = 1 ultraviolet intensity unit

INTERFACE OPTIONS
Use a SolData battery box (type 102DBX) and a standard digital voltmeter as your readout.
The 5 pole DIN connector is compatible with the widely used PASCO Science Workshop ®.

5 POLE DIN CONNECTOR PIN CONNECTIONS
PIN (1)Signal out
PIN (4)+5V to 12V supply
PIN (5)Ground
With this information you can connect the detector directly to your own data collection system.


APPLICATION NOTES


Use the 104DM digital display unit to display output directly in UVI, MED, mW/m2 or other ultraviolet irradiance units of your choice.

The detector DIN connector is compatible with the PASCO Science Workshop ® data logger system. To connect to any data logger use DIN connector pin 5 for ground, pin 1 for the signal and pin 4 for the +5 V to 12 V supply voltatge.


CALIBRATION


The SolData UVB detector uses a SiC photodiode with CIE 87 response.

The SolData detector was compared with a YES instrument at the Danish Met Office in Copenhagen over a period of several days.


UVB UNITS OF MEASUREMENT

The UVB detector output signal U is proportional to the product of the CIE response R(L) and the spectral irradiance I(L) of the source being measured where L is the wavelength. U = integral of R(L) I(L) dL over the region of interest. Because UVB data is most often used to describe the biological effects of the radiation, the unit MED per hour is commonly used. A dose of one MED will cause a detectable reddening of the skin for an average person. This value corresponds to a total dose of 210 J/m2.

A dose rate of 1 MED per hour corresponds to (210 J/m2)/3600 s = 58.3 mW/m2. The effective UV intensity (UVI) is defined so that 1 UVI = 25 mW/m2 . Thus 1 MED/hour equals 2.33 UVI. SolData UVB detectors are calibrated so that ca. 6 UVI will yield an output signal of about 1 volt.

Example: You measure an output signal of 2 volts. This corresponds to a dose rate of 12 UVI = (12/2.33) = 5.15 MED/h. Under these conditions one MED would be received by the average person in 60/5.15 i.e. about 12 minutes.

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