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/m2 and Btu4-1/2 digital displayData retention functionMeasure directly without adjustment. Steadily measure for a long periodProduct Name: Solar Power MeterModel: SM206Resolution: 0.1W/m2, 0.1 Btu/(ft2-h)Display: 4-1/2LCD display, maximum displayed numerical value 19999Error range: (10%R+2dgts) R:readingsTemperature error: 0.38W/m2 / [ 0.12 Btu/(ft2-h)/] deviation at 25Overload display: "OL"Range: 0.1-1999.9 W/m2, 0.1-1999.9 Btu/(ft2-h)Sampling time: 0.25t/sOperation temperature and humidity: 0C to 40C Less than 80%RHStorage temperature and humidity: -10C to 50C Less than 70%RHDrift: Less than 1.5% /yearDimensions and weight: 132(L) x 60(W) x 38 (H)mmWeight: . 150gPower Supply: 9V battery(NOT included)Battery operation life: . 100 hourscolor:As shownMaterial:plasticPackage Contents:1 x Solar Power MeterOnly 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.