Tube Solarimeter - TSL
The familiar black and white ‘Monteith pattern’ Tube Solarimeters were originally conceived in 1964, and since that time thousands have been used in agronomic studies throughout the world.
Tube Solarimeters are vital for measuring solar radiation in crop growth studies. Ideal for outside use, they may also be used under natural light in glasshouses, but artificial lighting of higher infra-red content than daylight may pose problems.
To measure the fractional transmission of solar radiation through a crop canopy, a number of tubes are placed beneath the canopy; each tube is 970mm long. Their arrangement depends on the uniformity of the whole crop stand. Each TSL tube has a bubble level for accurate horizontal mounting.
A reference measure of incident solar radiation above the canopy is needed throughout the growing season. A Dome Solarimeter is preferred, but a second tube solarimeter provides acceptable accuracy. If the transmission measurements are to be converted into quantum units, then a reference PAR Quantum Sensor is needed above the crop as well.
Tubes produce an output proportional to the irradiance of total solar energy. This is preset to 15mV per kW.m-2 by comparison with a standard Kipp dome solarimeter. The sensitivity varies to some extent with the angle of the solar beam to the tube axis. For good practice, users are recommended to recheck the calibration in a similar manner, under the conditions of their experiment.
For crop studies, the output from each tube is usually integrated over periods of a day or longer, during the growing season. The Delta-T DL2e Logger is ideal for this purpose.
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