Solar meters are compact, handheld radiometers with simple pushbutton operation and NIST-traceable accuracy. They're proudly made in the USA. The Solar meter Model 4. 0 Standard UVA Meter measures the UVA region from 320-400nm. Applications include monitoring UV lamp intensity and aging, measuring outdoor UVA, testing acrylic shield transmission, testing window film/transmission, and testing eyewear UVA blocking capabilities. To operate your Solar meter, aim the sensor window located on the top panel of the meter directly at a UV source. Press and hold the push-button switch on the face of the meter and read the results in mW/cm on the LCD screen. For best results take note of the distance the reading was taken from the UV source in order to ensure repeatable results. A 9V battery is included, along with a rugged carrying case and Calibration Certificate.