University of Helsinki
I am evaluating specifications of array detector spectroradiometers.
In the literature one can see them used sometimes for measuring UV-B in sunlight or in UV-B supplementation studies with plants. These single monochromator instruments are not good enough for this. They can overestimate erythemal doses by 100% or more in some cases. So, be careful when reading papers! The most popular brand is Ocean Optics. They are good for visible light measurements. However, with special measuring and calibration procedures they could be used to measure UV-B. I have not seen these special calibrations applied in research with plants, only in the recent methodological literature. I became aware of these from a reference sent to me by Prof. L.O. Bjorn, and investigating this possibilities is also part of the work of one of the technical work groups of the COST action UV4growth. One of the experts on this type of calibration is here in Helsinki, at STUK. I will contact him.
We will buy an array detector spectroradiometer, because they are portable, they measure all wavelengths simultaneously and because they are much cheaper. If the money is enough we will buy a dual channel model, so that we can measure simultaneously at two positions (e.g. inside and above a canopy) or with two different integration times to increase the dynamic range.
Currently we have a LI-COR LI-1800 on loan. This is a very good instrument for visible light measurements. It needs new batteries and scanning takes minutes. The long scanning time is not much of a problem for lamps, LEDs or under clear skies, but under broken clouds or inside canopies it is a bit of a problem. The LI-1800 is battery powered so it is fine for field work. The machine we are using is 18 years old. For UV measurements we have access to a Macam double monochromator spectroradiometer at our department. It is not our own but can be used. The problem is that it is big, heavy and mains powered. It is a relatively reliable machine, but certainly good enough for measuring UV-B in experiments.
These are the key manufacturers of array-detector USB-powered spectroradiometers:
Ocean Optics
Avantes
StellarNet
AstraNet
Iternational Light
Only the first three have versatile and user-friendly software. The last two do not seem to make dual channel instruments, but of course one could always buy two single channel instruments.
I’ll update this when I make some progress.
The following are references to the special calibration: spectral stray light corrections.
Ylianttila, L.; Visuri, R.; Huurto, L. & Jokela, K.
Evaluation of a single-monochromator diode array spectroradiometer for sunbed UV-radiation measurements.
Photochem Photobiol, 2005, 81, 333-341, STUK, Radiation and Nuclear Safety Authority, Non-Ionizing Radiation Laboratory, Helsinki, Finland.
Zong, Y.; Brown, S. W.; Johnson, B. C.; Lykke, K. R. & Ohno, Y.
Simple spectral stray light correction method for array spectroradiometers.
Appl Opt, 2006, 45, 1111-1119, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA.
Coleman, A.; Sarkany, R. & Walker, S.
Clinical ultraviolet dosimetry with a CCD monochromator array spectroradiometer.
Phys Med Biol, 2008, 53, 5239-5255, St Thomas’ NHS Foundation Trust, London SE1 7EH, UK.
This reference is about a test of a limited spectral range instrument:
Ansko, I.; Eerme, K.; Lätt, S.; Noorma, M. & Veismann, U.
Study of suitability of AvaSpec array spectrometer for solar UV field measurements
Atmospheric Chemistry and Physics, 2008, 8, 3247-3253