PHOTOTUBE-TYPE INTEGRATING LIGHT RECORDERS: A SUMMARY OF PERFORMANCE OVER A FIVE-YEAR PERIOD

Abstract

Phototube-type integrating light recorders with opal glass globe receivers (cf. Sprague and Williams, Plant Physiol. 18: 131-133. 1943) were constructed and tested under field conditions. When properly adjusted these gave a linear response to sunlight at intensities greater than about 100 f. c. They proved to be rugged and were portable. DC-operated units could be placed in weather instrument cabinets in the field and read once a week. They provided integrated values for the daily amount of light, which were correlated closely (r = 0.968, n = 285) with the inte- grated radiant energy values obtained with an Eppley pyrheliometer The phototube-type instrument is apparently less sensitive to the declination of the sun than the Eppley pyrheliometer.