How to Use: Just the button on the front of the device. Point the sensor window on the top panel of the meter directly at the UV source. Read the notes on the LCD screen and make notes as needed. To accurate data, run multiple tests at the same distance and average. Battery operating voltage is 3V to 2.5V. Below 2.5V the LCD number begin to darken, indicating the need for battery replacement. Specification: Item Type: UVA Meter Irradiance Range: 0-1999 μW/cm² UVA Response: λp=320-400 nm Resolution: 1 μW/cm² Conversion Rate: 3.0 Readings / Sec Display: 3.5-bit LCD Size: 0.4 Inches High Operating Temperature: 32℉ to 90℉ Operating Humidity: 5% to 80% RH Accuracy: +10% REF NIST Product Size: . 165 x 75 x 30mm / 6.5 x 3 x 1.2in Power Supply: 2x1 5V AA Battery (Shipped Without Battery) Lens: UV Glass Weight: . 231g / 0.5oz Material: Silicone+ABS colour: As shown Package Contents: 1 x UVA Meter Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.