Abstract
Abstract: A multi‐sensor system is described, based on a 1024 channel diode array spectrometer, to measure spectral radiant flux density in the range of 380 nm to 850 nm, with a resolution of 0.8 nm in minimal 16 milliseconds integration time per sensor (noon, clear sky conditions). 264 space‐integrating 4π sensors deployed in the canopies and 2 m above stand floor are sequentially connected to the spectrometer by means of 30‐m long fibre optics. During low‐level conditions (dawn, overcast sky) the system automatically lengthens the integration time of the spectrometer. About 3 sec per sensor, i.e., 13 min for the total of 264 sensors (worst case) are needed to collect spectral energy data, store them on hard disk and move the channel multiplexer to the next fibre optic position. The detection limit of quartz fibre sensors is 0.2 W/m 2 ; precision and absolute error of radiant flux density are smaller than 3 % and 10 %, respectively. The system, operating since 1999, is derived from a 20‐sensor pilot system developed for PAR measurements (PMMA fibre sensor, 400nm to 700 nm). Data achieved with the system serve to determine vertical profiles of wavelength dependent radiation extinction, with special respect to R/FR ratios and to develop a model of spectral radiation distribution in a mature forest stand, prerequisites for the computation of carbon gain of the stand and the evaluation of stand growth models.
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Claims 8
Claim · model-written summary
The canopy radiation instrument measured spectral flux over 380 nm to 850 nm.
Verbatim
e0“A multi‐sensor system is described, based on a 1024 channel diode array spectrometer, to measure spectral radiant flux density in the range of 380 nm to 850 nm, with a resolution of 0.8 nm in minimal 16 milliseconds integration time per sensor (noon, clear sky conditions).”
t0“Beech‐Spruce”
Claim · model-written summary
The instrument had 0.8 nm spectral resolution.
Verbatim
e0“A multi‐sensor system is described, based on a 1024 channel diode array spectrometer, to measure spectral radiant flux density in the range of 380 nm to 850 nm, with a resolution of 0.8 nm in minimal 16 milliseconds integration time per sensor (noon, clear sky conditions).”
t0“Beech‐Spruce”
Claim · model-written summary
The instrument integrated in a minimum 16 milliseconds per sensor at noon in clear sky.
Verbatim
e0“A multi‐sensor system is described, based on a 1024 channel diode array spectrometer, to measure spectral radiant flux density in the range of 380 nm to 850 nm, with a resolution of 0.8 nm in minimal 16 milliseconds integration time per sensor (noon, clear sky conditions).”
t0“Beech‐Spruce”
Claim · model-written summary
The system required about 3 sec per sensor in worst-case operation.
Verbatim
e0“About 3 sec per sensor, i.e., 13 min for the total of 264 sensors (worst case) are needed to collect spectral energy data, store them on hard disk and move the channel multiplexer to the next fibre optic position.”
t0“Beech‐Spruce”
Claim · model-written summary
The system required 13 min for 264 sensors in worst-case operation.
Verbatim
e0“About 3 sec per sensor, i.e., 13 min for the total of 264 sensors (worst case) are needed to collect spectral energy data, store them on hard disk and move the channel multiplexer to the next fibre optic position.”
t0“Beech‐Spruce”
Claim · model-written summary
Quartz fibre sensors had a 0.2 W/m 2 detection limit.
Verbatim
e0“The detection limit of quartz fibre sensors is 0.2 W/m 2 ; precision and absolute error of radiant flux density are smaller than 3 % and 10 %, respectively.”
t0“Beech‐Spruce”
Claim · model-written summary
Radiant flux density precision was below 3 %.
Verbatim
e0“The detection limit of quartz fibre sensors is 0.2 W/m 2 ; precision and absolute error of radiant flux density are smaller than 3 % and 10 %, respectively.”
t0“Beech‐Spruce”
Claim · model-written summary
Radiant flux density absolute error was below 10 %.
Verbatim
e0“The detection limit of quartz fibre sensors is 0.2 W/m 2 ; precision and absolute error of radiant flux density are smaller than 3 % and 10 %, respectively.”
t0“Beech‐Spruce”