1. The problem statement, all variables and given/known data Hello, I'm trying to use a solarimeter (thermopile) to measure the direct flux of solar radiation, in clear conditions, over varying solar zenith angles. The equipment has an output of volts, but I need to convert this to Lux and then convert this to watts per meter squared. How can I go about doing this as my light source has a mix of different wavelengths? I have also read that I can calculate the number of lumens per watt by using the luminosity function, but how could I get Watts per meter squared from this? Thank you.