Our UV Dosimeter system

The Scienterra UV Dosimeter is a small wearable device that measures personal UV exposure. It contains a UV sensor, microprocessor, and data storage. A single coin-cell battery keeps it running for about 12 months. Each data point is recorded as an individually timestamped measurement. The user can adjust the measurement sensitivity, the time interval between measurements, and the daily schedule.

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The dosimeter communicates via a proprietary wireless interface. A docking cradle connects to a computer's USB port. The cradle allows you to adjust configuration settings and download data. The data file can be processed with Excel, Matlab, IDL, or any data processing software.

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We offer a UVB dosimeter with a spectral response that closely matches the erythemal action spectrum. This is the type of UV radiation that causes sunburn. Most UVB rays are absorbed by atmospheric ozone, leaving only a small amount to reach the surface. Even at such reduced intensities, UVB exposure is hazardous, and is the leading cause of skin cancer.

This graph shows the spectral response function of the UVB sensor.

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We also offer a UVA dosimeter. The sensor measures UVA and UVB, but the atmosphere blocks most UVB rays. The UVA dosimeter accurately measures the radiation that passes through this atmospheric filter, which favors UVA by more than 99.5% (shaded area). There is a growing interest in UVA rays, which penetrate tissues, causing skin to age and thicken. UVA is also a carcinogen, and is linked to eye disease.

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A calibration compares a dosimeter to a reference instrument, under a range of UV radiation levels. Most researchers perform their own calibrations. To perform a calibration, you need a reference instrument, a rooftop, and a clear sky. Factory calibrations can also be provided if required.   

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The resulting calibration function converts raw data into useful radiation units, like UVI, or watts per square meter. Each dosimeter's calibration function is highly linear, so it's easy to perform the necessary calculation.  

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Once calibrated, dosimeters can provide ambient UV measurements with high accuracy and fine temporal resolution. In this example, the dosimeter (blue) reveals details about the afternoon clouds that are missed by the reference instrument (red).

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When looking at personal UV exposure, the dosimeter data will appear erratic. This is because of normal body movement. This example shows personal activity throughout the day, with episodes spent in sun, in shade, and indoors. When dosimeter data (blue) are calibrated and integrated, the accumulated daily dose (pink) can be calculated.

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