Unit conversion help

Tsonko Tsonev ttsonev at obzor.bio21.acad.bg
Sun Aug 24 13:29:32 EST 1997


In article <33F88EFA.8DB3A67E at mail.telepac.pt>, Monica Moura
<mtmoura at mail.telepac.pt> wrote:

> Please forgive me if this is too basic (or off topic) to post here, but
> I wonder if anyone could please help me with this conversion problem I
> have. How can I convert a value that is in lux (illuminance) to
> micromole*m^-2*sec^-1?
>
> Thanks in advance for your help,
>
> Best regards,
>
> Monica

Hi Monika,
Dr. Meunier is right writing "It depends on the spectrum of the source.
If I remember correctly, lux is relative to the human eye's sensitivity,
so conversions are approximative."

You can use the following conversion table suggested by LI-COR
(http://www.licor.com) and published also by Enoch & Kimball, eds.
(1985):

Conversion factors for converting 400 to 700 nm photometric values in
klux to 400 to 700 nm photosynthetic photon flux density (PPFD) in
micromole*m^-2*sec^-1

Light source
============
daylight		1 klux=18 micromole*m^-2*sec^-1
metal halide		1 klux=14 micromole*m^-2*sec^-1
sodium (HP)		1 klux=14 micromole*m^-2*sec^-1
mercury			1 klux=14 micromole*m^-2*sec^-1
white fluorescent	1 klux=12 micromole*m^-2*sec^-1
incandescent		1 klux=20 micromole*m^-2*sec^-1

References:
LI-COR, Radiation Measurement and Instrumentation, LI-COR, Inc.,
Lincoln, Nebraska, 1982, 49 pp.
Enoch H.Z., B.A.Kimball (eds.) Carbon Dioxide Enrichment of Greenhouse
Crops, vol. I CRC Press, Boca Raton, Florida, 1986, 182 pp.(here are
also other useful conversion tables)

Best regards,
T.Tsonev
--
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E-mail: ttsonev at obzor.bio21.acad.bg
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