The Solarmeter 6.5 UV Index Radiometer is a compact, handheld device which helps you understand the UVB levels within your reptile's enclosure. All UV light sources gradually lose output as they get older but this easy to use device will let you know when your UV tube needs to be replaced for a new one. For animals to thrive, it is important to have areas within their enclosure where they can access UVB in varying strengths as well as be without. Instructions for Use: Aim the sensor window located on the top panel of the meter directly at the UV source. Press and hold the push-button switch on the face of the meter. For best results take note of the distance the reading was taken from the UV source in order to ensure accurate repeatable results. - Compact. - Monitors UV Lamp intensity and ageing - Simple single-button operation - LCD Display