I can't get even similar irradiance values from a lamp.

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" <[email protected]>
Subject: Re: [Radiance-general] I can't get even similar irradiance
values from a lamp.
To: Radiance general discussion <[email protected]>
Message-ID: <[email protected]>
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.

------------------------------

Message: 3
Date: Sun, 15 Mar 2009 09:54:28 -0700
From: Greg Ward <[email protected]>
Subject: Re: [Radiance-general] I can't get even similar irradiance
values from a lamp.
To: Radiance general discussion <[email protected]>
Message-ID: <[email protected]>
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 <[email protected]>
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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