Features This meter is a precision instrument measuring the intensity of sunlight. There are two units that can be selected: W/m² and Btu.Measure directly without adjustment, steadily measure for a long period. It supports maximum value hold function and data hold function. It can also be used to measure the light transmission intensity of glass to verify the performance of the glass, for example, car window performance test. Widely used for solar radiation measurement, solar energy research, meteorology, agriculture, physical and optical experiments. Specification:Model: SM206 Resolution: 0.1W/m², 0.1Btu/(ft²-h) Range Error: ± (10%R+2dgts)R: readingsTemperature Error: ±0.38W/m²/℃[±0.12Btu/(ft²-h)/℃] deviation at 25°C Display: 4-1/2 LCD display, maximum display numerical value 19999 Overload Display: "OL" Shift: <±1.5% /year Measurement Range: 0.1-1999.9W/m², 0.1-1999.9Btu/(ft²-h) Sampling Time: 2.5 seconds/time Operating Temperature and Humidity: 0~40℃,  <80%RH Storage Temperature and Humidity: -10~50℃, <70%RH Battery: 9V battery (NOT included)Size: Approx. 132 x 60 x 38mm / 5.2 x 2.4 x 1.5inWeight: 325g / 11.5oz (approx.) Package list: 1 * Solar Radiation Measuring Instrument (battery is NOT included)1 * User Manual1 * Packing Box  Package List 1 * Solar Radiation Measuring Instrument (battery is NOT included) 1 * User Manual 1 * Packing Box