[Radiance-general] Re: Re: I can't get even similar irradiance values$B!!(Bfrom$B!!(Ba lamp.

[Minki sung]

Dear Lars and Greg,

Thank you for your replying. As you said, the reflectance for UV is usually
lower than that for visible light. Actually, the box is an air handling unit
and the materials are mostly galvanized copper plates and the reflectance of
it for UV is referred from other reference. I thought the result might be
caused by incorrect reflectance so I have checked the values when only
direct components were calculated by deleting -ab option. The values dropped
eventually but were higher than those of experiment yet. I'm checking if
there are problems with the lamp model.

Sung


Message: 2
Date: Sun, 15 Mar 2009 23:18:57 +0800
From: "Lars O. Grobe" <lars.grobe at nus.edu.sg>
Subject: Re: [Radiance-general] I can't get even similar irradiance
	values	from	a lamp.
To: Radiance general discussion <radiance-general at radiance-online.org>
Message-ID: <49BD1C61.10300 at nus.edu.sg>
Content-Type: text/plain; charset=ISO-8859-1

Hi,

are you sure the material properties of the box match those you use in
your experiment? How did you define the materials?

Lars.



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Message: 3
Date: Sun, 15 Mar 2009 09:54:28 -0700
From: Greg Ward <gregoryjward at gmail.com>
Subject: Re: [Radiance-general] I can't get even similar irradiance
	values	from a lamp.
To: Radiance general discussion <radiance-general at radiance-online.org>
Message-ID: <A45DA6FC-7D4E-4B42-82EF-7FDD5CBECC3B at lmi.net>
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed

How did you measure the UV reflectance of the surfaces of your box?   
Most paints drop off dramatically from the visible spectrum to UV.   
White paints may re-emit UV as visible so they appear "whiter" under  
daylight illumination.  You really need to know the behavior of your  
paint with respect to ultraviolet wavelengths to do this correctly.

-Greg

> From: Minki Sung <minki.sung at gmail.com>
> Date: March 14, 2009 10:52:03 PM PDT
>
> Dear Radiance users,
>
> I'm writing here for third time and I always sorry for just asking.  
> I'm modeling a small box has a several bared cylindrical  
> fluorescent lamps (actually UV lamps) inside and want to know the  
> irradiance level on the surfaces of the box. The cylindrical lamps  
> has 32mm in diameter and 540mm in length and The radiance of 44W/sr/ 
> m2 calculated with the UV output of the lamps (7.5W) was applied to  
> the lamps. Before calculating the small box model I checked  
> irradiance values with an experiment measuring UV intensity at the  
> distance of 1 m and compared that with the same simple RADIANCE  
> calculation and the result was reasonable. However, the calculation  
> results are higher than those of experiments by 2~4 times with the  
> small box model. The small box is not simple but not so  
> complicated. I have modeled the lamp both as a cylinder and 72  
> polygons  but there were not so much changes. Only one channel was  
> used to calculate irradiances of UV from modeling to issuing  
> results and only diffused reflections were assumed. Geometric  
> errors or abnormal radiance distributions of lamps could be assumed  
> to cause the discrepancy, but 2~5 times are too large
> Here is my rtrace options.
>
> cat pts_sensor.pts | rtrace -I -oov -ar 128 -ad 512 -as 256 -ab 2 - 
> ds 0.02 uv.oct > uv.dat
>
> It would be appreciated if anyone give me advice.
>
>
> Sung



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