Designing a solar chamber

[MikeNoon]

I need to design a solar testing chamber that my client is basing on MIL-STD-810F, where they prescribe a range of illuminance from 55 to 1140W/m^2,delivered to three different sides of a 4' cube.

Using the conversion formula of 683 x 1140W/m^2 would give us a delivered amount of 778,620 lux, or roughly 77,800 foot-candles, per side of the cube. This would be roughly seven times the level of natural sunlight on a cloudless day, which is approximately 10,000 fc. Is this conversion and requirement correct, or is my customer looking for too high a level of illumination?

I can't figure out how I can fit enough luminaires around a 4' cube object to deliver that much light, in the required spectral mix of HPS and MV. Any ideas, or experience with these testing chambers to offer? Thanks in advance.
Mike Noon LC
Palindrome Lighting Design, Inc.

 

[IRstuff]

You indeed have all the correct numbers, but, unfortunately, they relate to apples and oranges. the 683 lm/W luminous efficacy, relates to in-band photopic illuminance, which is limited to 380 to 780 nm.

1150 W/m² relates to TOTAL solar irradiance, which every wavelength from 0 to infinity, based on Planck's blackbody radiation function.

The cheesy solution is to simply scale the 1150 W/m² to 100,000 lux, and ratio the 55 W/m² accordingly TTFN

 

[MikeNoon]

Thanks for the reply. So how does one determine how much "light" to throw on the subject object, once you have determined sources that supply the required spectral content? Is 100,000 lux (10K fc) the accepted norm within the testing industry? I can manage to configure a system that delivers 100,000 lux around the 4' test object, but 8 times that amount is a real problem.
Thanks,
Mike

 

[IRstuff]

I apologize for not asking what the intent of the requirement is. In most of the systems I deal with, the MIL-HDBK-310 condition is translated into an additional thermal load. Our systems are electro-optical, so the actual light load is tested as part of the sensor requirement and never tested at the system level.

As I was indicating last night, the 100,000 lux would be equivalent to the 1140 W/m^2, although it would need to be supplied from 5900K color temp sources to be correct. TTFN

 

[MikeNoon]

Aha....thanks for the clarification. I've got three different lamp sources to consider using, but the intensity had me confused. There are 4000w metal halides that meet the MIL-STD-810 spectrum range, or a combination of HPS and MV in a 2.1:1 ratio. I'll work them up and see what my client prefers. Thanks again.
Mike