This meter is a for measuring light intensity. It is used in solar radiation measurement, solar research, physical and optical experiments, meteorology, and agriculture. It can also be used to measure glass light intensity to verify glass properties. For example: Measurement of light intensity through vehicle windows. Selectable from two units: W or m2 and Btu 4-1 or 2 digital display Data retention function Measure directly without adjustment. Steadily measure for a long period Product Name: Solar Power Meter Model: SM206 Resolution: 0.1W or m2, 0.1 Btu or (ft2-h) Display: 4-1 or 2LCD display, maximum displayed numerical value 19999 Error range: (10 percent Rand2dgts) R:readings Temperature error: 0.38W or m2 or [ 0.12 Btu or (ft2-h) or ] deviation at 25 Overload display: "OL" Range: 0.1-1999.9 W or m2, 0.1-1999.9 Btu or (ft2-h) Sampling time: 0.25t or s Operation temperature and humidity: 0C to 40C Less than 80 percent RH Storage temperature and humidity: -10C to 50C Less than 70 percent RH Drift: Less than 1.5 percent or year Dimensions and weight: 132(L) x 60(W) x 38 (H)mm Weight: . 150g Power Supply: 9V battery(NOT included) Battery operation life: . 100 hours color:As shown Material:plastic Package Contents: 1 x Solar Power 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.