Fast-response pyrheliometer DR20-A1, DR15-A1

DR20 and DR15 are high-accuracy direct (normal incidence) solar radiation sensors, or pyrheliometers. DR20 complies with the Class A, and DR15 with the Class B specifications of the ISO 9060:2018 standard. These instruments are used in tracker-mounted operation, and offer analogue millivolt outputs. Both pyrheliometers have superior window heating that leads to high data availability. Hukseflux model DR15 pyrheliometer is an ISO 9060 spectrally flat Class B (old ISO classification “first class”) instrument. It replaces the models DR01, DR02 and DR03. DR20 is a new Class A instrument. It has a better temperature response than DR15. Both instruments offer the highest accuracy and highest data availability, featuring window heating at low offsets. At the same heating power, the heating has been improved with a factor 4, at a 4 times lower offset! DR20 and DR15 are applied in high-accuracy measurement of the solar radiation received by a plane surface from a 5 ° full field of view angle. This quantity, expressed in W/m2, is called “direct” solar radiation or DNI (direct normal irradiance). It is necessary to keep the instrument pointed at the sun by using a two-axis tracker. High data availability is attained by heating of the front window. This suppresses dew and frost deposition at a very low power consumption: DR20 / DR15 needs only 1 W to keep its window free from dew and frost. Using DR20 / DR15 pyrheliometers offer significant benefits over the use of competing models. The pyrheliometers offer the highest accuracy and highest data availability, featuring heating at low offsets.