FeaturesLight Transmittance of window filmWide spectral range.Excellent long term stability.Cosine corrected.Automatic transmission measurements.Select either power or transmission.Solar energy power or transmission.Current time setting function.User calibration factor setting function.End-mount light sensor.Select either W/m2 or Btu / (ft2*h) unitsData Hold / MAX / AVG modes.Data Memory and Read function. (99 sets.)SpecificationDisplay:3-1/2 digits.Max.indication1999Range:2000W/m ,2 634Btu/(ft 2 * h)Resolution:1W/m21Btu/(ft2*h)Spectral response:400-1100nmAccuracy:Typically within ± 10W/m2[ ±3 Btu / (ft2*h) ] or ±5% , whichever is greater in sunlight; Additional temperature induced error ±0.38W/m2 / [ ±0.12 Btu / (ft2*h)/ ] from 25Angular accuracy:Cosine corrected <5% for angles <60 °Drift:<±2% / per yearCalibration:User recalibration availableOver-input:Display shows" "Sampling Time:Approx. 0.4 secondManu data memory and read:99 setsBattery:4pcs size AAA(Not included)Battery Life:Approx. 100 hoursOperating temp and humidity:0 to 50 below 80%RHStorage temp and Humidity:-10 to 60 below 70% RHWeight:Approx. 165gDimension:111(L)*64(W)*34(H)mmAccessories:Carrying Case, Operation Manual