Radiant power vs. irradiance

[jspec26]

Alright, I'm new to the forum, and I've got to say, it is quite impressive. Okay, my question: How do I convert radiant power (uW/10nm/Lumens) to W/m^2? I am conducting a simulated solar radiation test. I need to know the spectral power distribution of a certain metal hallide bulb. The manufacturer provided a chart of radiant power/wavelength. The standard I'm testing to (MIL-STD-810F) has tolerance bands in the UV, VIS, and IR that the bulb must conform to. The values given are in W/m^2. I have an eppley pyranometer, but it measures irradiance across the whole spectrum, I do not have filters available at this time. I'm sure there's got to be some formula for this. I have not taken calc yet, but have support from several engineers here as far as the math goes. Any help would be appreciated. Thanks!

 

[Nate810]

To convert radiant power (uW/10nm/Lumens) to W/m^2, you will need to convert the radiation intensity based on the wavelength of the light source. This can be done using the following formula:Radiant Power (in uW/10nm/Lumens) x (Wavelength in nm / 1000) = Radiant Power (in W/m^2).For example, if you have a metal halide bulb with a radiant power of 500 uW/10nm/Lumens at a wavelength of 450 nm, then the corresponding radiant power in W/m^2 would be 0.45 W/m^2.Once you have calculated the radiant power for each wavelength, you can then use this data to compare it to the tolerance bands in the UV, VIS, and IR that the bulb must conform to in order to pass the MIL-STD-810F test.

 

[kyle8921]

Radiant power and irradiance are two different measures of the amount of electromagnetic energy emitted by a source. Radiant power, measured in watts (W), is the total amount of energy emitted by a source, while irradiance, measured in watts per square meter (W/m^2), is the amount of energy received per unit area. In other words, radiant power is the total energy output of a source, while irradiance is the intensity of that energy at a particular location.

To convert from radiant power to irradiance, you will need to know the distance from the source and the area over which the irradiance is being measured. The formula for this conversion is:

Irradiance = Radiant power / (4 * π * distance^2)

In this formula, distance is measured in meters and irradiance is in W/m^2. This formula assumes that the source is spherical and that the irradiance is being measured at a distance much greater than the size of the source.

In your case, you will need to use the measured radiant power for the specific wavelengths of interest and the distance from the source to calculate the irradiance at those wavelengths. This will allow you to compare the irradiance values to the tolerance bands specified in the MIL-STD-810F standard.

It is also important to note that the eppley pyranometer measures total irradiance across the whole spectrum, so you will need to use filters to isolate the specific wavelengths of interest in order to accurately measure the irradiance at those wavelengths. Without filters, your measurements may include energy from other wavelengths that could affect the accuracy of your results.

I hope this helps and good luck with your simulated solar radiation test!