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Photosynthetic Light Sensor for Measurements in Plant Canopies 1
Author(s) -
Norman J. M.,
Tanner C. B.,
Thurtell G. W.
Publication year - 1969
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1969.00021962006100060004x
Subject(s) - infrared , wavelength , signal (programming language) , optoelectronics , materials science , detector , optics , photosynthesis , photodetector , quantum efficiency , amplifier , physics , chemistry , computer science , biochemistry , cmos , programming language
A photosynthetic light sensor is described, which is based on experimental evidence that absorbed quanta at various wavelengths in the visible region (400‐700 nm) are nearly equally effective in initiating photosynthesis. Silicon photovoltaic cells are used as light detectors and their spectral response tailorded with Wratten filters to provide quantum response. A sharp near‐infrared cutoff is obtained by subtracting the signal of a cell sensing only the infrared from the signal of the cell sensing both the visible and infrared wavelengths. This pair of cells is then placed under heat absorbing glass to further reduce their differences. The differenced current signals from the cells are fed directly into an operational amplifier designed for current amplification. A fair cosine rtsponse is obtained by using a flat piece of diffusing plastic as the uppermost part of the sensor. Calculations and measurements are made to estimate errors resulting from imperfections in spectral tailoring and cosine correction.